Merge commit 'df552ff53e' into progress-bar

.github/workflows/ci.yml

@@ -1,4 +1,4 @@
-name: "Test"
+name: "CI"
 
 on:
   pull_request:
@@ -25,7 +25,7 @@ jobs:
         name: '${{ env.CACHIX_NAME }}'
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-    - run: nix-build -A checks.$(nix-instantiate --eval -E '(builtins.currentSystem)')
+    - run: nix --experimental-features 'nix-command flakes' flake check -L
 
   check_cachix:
     name: Cachix secret present for installer tests
@@ -74,3 +74,35 @@ jobs:
         install_url: '${{needs.installer.outputs.installerURL}}'
         install_options: "--tarball-url-prefix https://${{ env.CACHIX_NAME }}.cachix.org/serve"
     - run: nix-instantiate -E 'builtins.currentTime' --eval
+
+  docker_push_image:
+    needs: [check_cachix, tests]
+    if: >-
+      github.event_name == 'push' &&
+      github.ref_name == 'master' &&
+      needs.check_cachix.outputs.secret == 'true'
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2.4.0
+      with:
+        fetch-depth: 0
+    - uses: cachix/install-nix-action@v16
+    - run: echo CACHIX_NAME="$(echo $GITHUB_REPOSITORY-install-tests | tr "[A-Z]/" "[a-z]-")" >> $GITHUB_ENV
+    - run: echo NIX_VERSION="$(nix-instantiate --eval -E '(import ./default.nix).defaultPackage.${builtins.currentSystem}.version' | tr -d \")" >> $GITHUB_ENV
+    - uses: cachix/cachix-action@v10
+      if: needs.check_cachix.outputs.secret == 'true'
+      with:
+        name: '${{ env.CACHIX_NAME }}'
+        signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'
+        authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+    - run: nix --experimental-features 'nix-command flakes' build .#dockerImage -L
+    - run: docker load -i ./result/image.tar.gz
+    - run: docker tag nix:$NIX_VERSION nixos/nix:$NIX_VERSION
+    - run: docker tag nix:$NIX_VERSION nixos/nix:master
+    - name: Login to Docker Hub
+      uses: docker/login-action@v1
+      with:
+        username: ${{ secrets.DOCKERHUB_USERNAME }}
+        password: ${{ secrets.DOCKERHUB_TOKEN }}
+    - run: docker push nixos/nix:$NIX_VERSION
+    - run: docker push nixos/nix:master

.gitignore

@@ -120,3 +120,7 @@ GTAGS
 compile_commands.json
 
 nix-rust/target
+
+result
+
+.vscode/

.version

@@ -1 +1 @@
-2.6.0
+2.7.0

Makefile

@@ -10,7 +10,6 @@ makefiles = \
   src/libexpr/local.mk \
   src/libcmd/local.mk \
   src/nix/local.mk \
-  src/nlohmann/local.mk \
   src/resolve-system-dependencies/local.mk \
   scripts/local.mk \
   misc/bash/local.mk \

Makefile.config.in

@@ -16,6 +16,7 @@ LDFLAGS = @LDFLAGS@
 LIBARCHIVE_LIBS = @LIBARCHIVE_LIBS@
 LIBBROTLI_LIBS = @LIBBROTLI_LIBS@
 LIBCURL_LIBS = @LIBCURL_LIBS@
+LOWDOWN_LIBS = @LOWDOWN_LIBS@
 OPENSSL_LIBS = @OPENSSL_LIBS@
 LIBSECCOMP_LIBS = @LIBSECCOMP_LIBS@
 PACKAGE_NAME = @PACKAGE_NAME@

configure.ac

@@ -262,13 +262,17 @@ fi
 PKG_CHECK_MODULES([GTEST], [gtest_main])
 
 
+# Look for nlohmann/json.
+PKG_CHECK_MODULES([NLOHMANN_JSON], [nlohmann_json >= 3.9])
+
+
 # documentation generation switch
 AC_ARG_ENABLE(doc-gen, AS_HELP_STRING([--disable-doc-gen],[disable documentation generation]),
   doc_generate=$enableval, doc_generate=yes)
 AC_SUBST(doc_generate)
 
 # Look for lowdown library.
-PKG_CHECK_MODULES([LOWDOWN], [lowdown >= 0.8.0], [CXXFLAGS="$LOWDOWN_CFLAGS $CXXFLAGS"])
+PKG_CHECK_MODULES([LOWDOWN], [lowdown >= 0.9.0], [CXXFLAGS="$LOWDOWN_CFLAGS $CXXFLAGS"])
 
 # Setuid installations.
 AC_CHECK_FUNCS([setresuid setreuid lchown])

default.nix

@@ -1,3 +1,3 @@
-(import (fetchTarball https://github.com/edolstra/flake-compat/archive/master.tar.gz) {
+(import (fetchTarball "https://github.com/edolstra/flake-compat/archive/master.tar.gz") {
   src = ./.;
 }).defaultNix

doc/manual/generate-builtins.nix

@@ -6,9 +6,9 @@ builtins:
 concatStrings (map
   (name:
     let builtin = builtins.${name}; in
-    "<dt><code>${name} "
+    "<dt id=\"builtins-${name}\"><a href=\"#builtins-${name}\"><code>${name} "
     + concatStringsSep " " (map (s: "<var>${s}</var>") builtin.args)
-    + "</code></dt>"
+    + "</code></a></dt>"
     + "<dd>\n\n"
     + builtin.doc
     + "\n\n</dd>"

doc/manual/generate-options.nix

@@ -20,7 +20,7 @@ concatStrings (map
          # JSON, but that converts to "{ }" here.
          (if isAttrs option.value then "`\"\"`"
           else "`" + toString option.value + "`")) + "\n\n"
-       else "    **Default:** *machine-specific*")
+       else "    **Default:** *machine-specific*\n")
     + (if option.aliases != []
        then "    **Deprecated alias:** " + (concatStringsSep ", " (map (s: "`${s}`") option.aliases)) + "\n\n"
        else "")

doc/manual/local.mk

@@ -72,6 +72,7 @@ $(d)/builtins.json: $(bindir)/nix
 	@mv $@.tmp $@
 
 # Generate the HTML manual.
+html: $(docdir)/manual/index.html
 install: $(docdir)/manual/index.html
 
 # Generate 'nix' manpages.

doc/manual/src/SUMMARY.md.in

@@ -72,6 +72,7 @@
   - [CLI guideline](contributing/cli-guideline.md)
 - [Release Notes](release-notes/release-notes.md)
   - [Release X.Y (202?-??-??)](release-notes/rl-next.md)
+  - [Release 2.6 (2022-01-24)](release-notes/rl-2.6.md)
   - [Release 2.5 (2021-12-13)](release-notes/rl-2.5.md)
   - [Release 2.4 (2021-11-01)](release-notes/rl-2.4.md)
   - [Release 2.3 (2019-09-04)](release-notes/rl-2.3.md)

doc/manual/src/command-ref/nix-shell.md

@@ -101,7 +101,8 @@ The following common options are supported:
 
   - `NIX_BUILD_SHELL`\
     Shell used to start the interactive environment. Defaults to the
-    `bash` found in `PATH`.
+    `bash` found in `<nixpkgs>`, falling back to the `bash` found in
+    `PATH` if not found.
 
 # Examples
 

doc/manual/src/command-ref/nix-store.md

@@ -321,8 +321,8 @@ symlink.
     This query has one option:
 
       - `--include-outputs`
-        Also include the output path of store derivations, and their
-        closures.
+        Also include the existing output paths of store derivations,
+        and their closures.
 
     This query can be used to implement various kinds of deployment. A
     *source deployment* is obtained by distributing the closure of a

doc/manual/src/expressions/language-constructs.md

@@ -284,6 +284,10 @@ The points of interest are:
     function is called with the `localServer` argument set to `true` but
     the `db4` argument set to `null`, then the evaluation fails.
 
+    Note that `->` is the [logical
+    implication](https://en.wikipedia.org/wiki/Truth_table#Logical_implication)
+    Boolean operation.
+
 2.  This is a more subtle condition: if Subversion is built with Apache
     (`httpServer`) support, then the Expat library (an XML library) used
     by Subversion should be same as the one used by Apache. This is

doc/manual/src/release-notes/rl-2.4.md

@@ -276,6 +276,9 @@ more than 2800 commits from 195 contributors since release 2.3.
 
 * Plugins can now register `nix` subcommands.
 
+* The `--indirect` flag to `nix-store --add-root` has become a no-op.
+  `--add-root` will always generate indirect GC roots from now on.
+
 ## Incompatible changes
 
 * The `nix` command is now marked as an experimental feature. This

doc/manual/src/release-notes/rl-2.6.md

@@ -0,0 +1,21 @@
+# Release 2.6 (2022-01-24)
+
+* The Nix CLI now searches for a `flake.nix` up until the root of the current
+  Git repository or a filesystem boundary rather than just in the current
+  directory.
+* The TOML parser used by `builtins.fromTOML` has been replaced by [a
+  more compliant one](https://github.com/ToruNiina/toml11).
+* Added `:st`/`:show-trace` commands to `nix repl`, which are used to
+  set or toggle display of error traces.
+* New builtin function `builtins.zipAttrsWith` with the same
+  functionality as `lib.zipAttrsWith` from Nixpkgs, but much more
+  efficient.
+* New command `nix store copy-log` to copy build logs from one store
+  to another.
+* The `commit-lockfile-summary` option can be set to a non-empty
+  string to override the commit summary used when commiting an updated
+  lockfile.  This may be used in conjunction with the `nixConfig`
+  attribute in `flake.nix` to better conform to repository
+  conventions.
+* `docker run -ti nixos/nix:master` will place you in the Docker
+  container with the latest version of Nix from the `master` branch.

doc/manual/src/release-notes/rl-next.md

@@ -1,8 +1,28 @@
 # Release X.Y (202?-??-??)
 
-* The TOML parser used by `builtins.fromTOML` has been replaced by [a
-  more compliant one](https://github.com/ToruNiina/toml11).
-* Added `:st`/`:show-trace` commands to nix repl, which are used to
-  set or toggle display of error traces.
-* New builtin function `builtins.zipAttrsWith` with same functionality
-  as `lib.zipAttrsWith` from nixpkgs, but much more efficient.
+* A number of "default" flake output attributes have been
+  renamed. These are:
+
+  * `defaultPackage.<system>` → `packages.<system>.default`
+  * `defaultApps.<system>` → `apps.<system>.default`
+  * `defaultTemplate` → `templates.default`
+  * `defaultBundler.<system>` → `bundlers.<system>.default`
+  * `overlay` → `overlays.default`
+  * `devShell.<system>` → `devShells.<system>.default`
+
+  The old flake output attributes still work, but `nix flake check`
+  will warn about them.
+
+* `nix bundle` breaking API change now supports bundlers of the form
+  `bundler.<system>.<name>= derivation: another-derivation;`. This supports
+  additional functionality to inspect evaluation information during bundling. A
+  new [repository](https://github.com/NixOS/bundlers) has various bundlers
+  implemented.
+
+* `nix store ping` now reports the version of the remote Nix daemon.
+
+* `nix flake {init,new}` now display information about which files have been
+  created.
+
+* Templates can now define a `welcomeText` attribute, which is printed out by
+  `nix flake {init,new} --template <template>`.

docker.nix

@@ -21,6 +21,7 @@ let
     cacert.out
     findutils
     iana-etc
+    git
   ];
 
   users = {
@@ -200,6 +201,8 @@ let
 
       mkdir $out/tmp
 
+      mkdir -p $out/var/tmp
+
       mkdir -p $out/etc/nix
       cat $nixConfContentsPath > $out/etc/nix/nix.conf
 
@@ -235,6 +238,7 @@ pkgs.dockerTools.buildLayeredImageWithNixDb {
   '';
   fakeRootCommands = ''
     chmod 1777 tmp
+    chmod 1777 var/tmp
   '';
 
   config = {

flake.lock

@@ -31,10 +31,26 @@
         "type": "indirect"
       }
     },
+    "nixpkgs-regression": {
+      "locked": {
+        "lastModified": 1643052045,
+        "narHash": "sha256-uGJ0VXIhWKGXxkeNnq4TvV3CIOkUJ3PAoLZ3HMzNVMw=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "github"
+      },
+      "original": {
+        "id": "nixpkgs",
+        "rev": "215d4d0fd80ca5163643b03a33fde804a29cc1e2",
+        "type": "indirect"
+      }
+    },
     "root": {
       "inputs": {
         "lowdown-src": "lowdown-src",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-regression": "nixpkgs-regression"
       }
     }
   },

flake.nix

@@ -2,9 +2,10 @@
   description = "The purely functional package manager";
 
   inputs.nixpkgs.url = "nixpkgs/nixos-21.05-small";
+  inputs.nixpkgs-regression.url = "nixpkgs/215d4d0fd80ca5163643b03a33fde804a29cc1e2";
   inputs.lowdown-src = { url = "github:kristapsdz/lowdown"; flake = false; };
 
-  outputs = { self, nixpkgs, lowdown-src }:
+  outputs = { self, nixpkgs, nixpkgs-regression, lowdown-src }:
 
     let
 
@@ -132,6 +133,7 @@
                 ./boehmgc-coroutine-sp-fallback.diff
               ];
             }))
+            nlohmann_json
           ];
 
         perlDeps =
@@ -205,7 +207,8 @@
         installCheckPhase = "make installcheck -j$NIX_BUILD_CORES -l$NIX_BUILD_CORES";
       };
 
-      binaryTarball = buildPackages: nix: pkgs: let
+      binaryTarball = buildPackages: nix: pkgs:
+        let
           inherit (pkgs) cacert;
           installerClosureInfo = buildPackages.closureInfo { rootPaths = [ nix cacert ]; };
         in
@@ -299,6 +302,8 @@
 
             propagatedBuildInputs = propagatedDeps;
 
+            disallowedReferences = [ boost ];
+
             preConfigure =
               ''
                 # Copy libboost_context so we don't get all of Boost in our closure.
@@ -310,6 +315,13 @@
                   chmod u+w $out/lib/*.so.*
                   patchelf --set-rpath $out/lib:${currentStdenv.cc.cc.lib}/lib $out/lib/libboost_thread.so.*
                 ''}
+                ${lib.optionalString currentStdenv.isDarwin ''
+                  for LIB in $out/lib/*.dylib; do
+                    chmod u+w $LIB
+                    install_name_tool -id $LIB $LIB
+                  done
+                  install_name_tool -change ${boost}/lib/libboost_system.dylib $out/lib/libboost_system.dylib $out/lib/libboost_thread.dylib
+                ''}
               '';
 
             configureFlags = configureFlags ++
@@ -326,6 +338,12 @@
             postInstall = ''
               mkdir -p $doc/nix-support
               echo "doc manual $doc/share/doc/nix/manual" >> $doc/nix-support/hydra-build-products
+              ${lib.optionalString currentStdenv.isDarwin ''
+              install_name_tool \
+                -change ${boost}/lib/libboost_context.dylib \
+                $out/lib/libboost_context.dylib \
+                $out/lib/libnixutil.dylib
+              ''}
             '';
 
             doInstallCheck = true;
@@ -429,19 +447,7 @@
         installerScriptForGHA = installScriptFor [ "x86_64-linux" "x86_64-darwin" "armv6l-linux" "armv7l-linux"];
 
         # docker image with Nix inside
-        dockerImage = nixpkgs.lib.genAttrs linux64BitSystems (system:
-          let
-            pkgs = nixpkgsFor.${system};
-            image = import ./docker.nix { inherit pkgs; tag = version; };
-          in pkgs.runCommand "docker-image-tarball-${version}"
-            { meta.description = "Docker image with Nix for ${system}";
-            }
-            ''
-              mkdir -p $out/nix-support
-              image=$out/image.tar.gz
-              ln -s ${image} $image
-              echo "file binary-dist $image" >> $out/nix-support/hydra-build-products
-            '');
+        dockerImage = nixpkgs.lib.genAttrs linux64BitSystems (system: self.packages.${system}.dockerImage);
 
         # Line coverage analysis.
         coverage =
@@ -495,6 +501,12 @@
           inherit (self) overlay;
         });
 
+        tests.sourcehutFlakes = (import ./tests/sourcehut-flakes.nix rec {
+          system = "x86_64-linux";
+          inherit nixpkgs;
+          inherit (self) overlay;
+        });
+
         tests.setuid = nixpkgs.lib.genAttrs
           ["i686-linux" "x86_64-linux"]
           (system:
@@ -503,29 +515,23 @@
               inherit (self) overlay;
             });
 
-        /*
-        # Check whether we can still evaluate all of Nixpkgs.
+        # Make sure that nix-env still produces the exact same result
+        # on a particular version of Nixpkgs.
         tests.evalNixpkgs =
-          import (nixpkgs + "/pkgs/top-level/make-tarball.nix") {
-            # FIXME: fix pkgs/top-level/make-tarball.nix in NixOS to not require a revCount.
-            inherit nixpkgs;
-            pkgs = nixpkgsFor.x86_64-linux;
-            officialRelease = false;
-          };
-
-        # Check whether we can still evaluate NixOS.
-        tests.evalNixOS =
           with nixpkgsFor.x86_64-linux;
           runCommand "eval-nixos" { buildInputs = [ nix ]; }
             ''
-              export NIX_STATE_DIR=$TMPDIR
-
-              nix-instantiate ${nixpkgs}/nixos/release-combined.nix -A tested --dry-run \
-                --arg nixpkgs '{ outPath = ${nixpkgs}; revCount = 123; shortRev = "abcdefgh"; }'
-
-              touch $out
+              type -p nix-env
+              # Note: we're filtering out nixos-install-tools because https://github.com/NixOS/nixpkgs/pull/153594#issuecomment-1020530593.
+              time nix-env --store dummy:// -f ${nixpkgs-regression} -qaP --drv-path | sort | grep -v nixos-install-tools > packages
+              [[ $(sha1sum < packages | cut -c1-40) = ff451c521e61e4fe72bdbe2d0ca5d1809affa733 ]]
+              mkdir $out
             '';
-        */
+
+        metrics.nixpkgs = import "${nixpkgs-regression}/pkgs/top-level/metrics.nix" {
+          pkgs = nixpkgsFor.x86_64-linux;
+          nixpkgs = nixpkgs-regression;
+        };
 
         installTests = forAllSystems (system:
           let pkgs = nixpkgsFor.${system}; in
@@ -547,9 +553,9 @@
         binaryTarball = self.hydraJobs.binaryTarball.${system};
         perlBindings = self.hydraJobs.perlBindings.${system};
         installTests = self.hydraJobs.installTests.${system};
-      } // (if system == "x86_64-linux" then {
+      } // (nixpkgs.lib.optionalAttrs (builtins.elem system linux64BitSystems)) {
         dockerImage = self.hydraJobs.dockerImage.${system};
-      } else {}));
+      });
 
       packages = forAllSystems (system: {
         inherit (nixpkgsFor.${system}) nix;
@@ -594,6 +600,20 @@
 
           hardeningDisable = [ "pie" ];
         };
+        dockerImage =
+          let
+            pkgs = nixpkgsFor.${system};
+            image = import ./docker.nix { inherit pkgs; tag = version; };
+          in
+          pkgs.runCommand
+            "docker-image-tarball-${version}"
+            { meta.description = "Docker image with Nix for ${system}"; }
+            ''
+              mkdir -p $out/nix-support
+              image=$out/image.tar.gz
+              ln -s ${image} $image
+              echo "file binary-dist $image" >> $out/nix-support/hydra-build-products
+            '';
       } // builtins.listToAttrs (map (crossSystem: {
         name = "nix-${crossSystem}";
         value = let
@@ -637,8 +657,7 @@
         nixpkgsFor.${system}.lib.nameValuePair
           "nix-${stdenvName}"
           nixpkgsFor.${system}."${stdenvName}Packages".nix
-      ) stdenvs))
-      );
+      ) stdenvs)));
 
       defaultPackage = forAllSystems (system: self.packages.${system}.nix);
 

maintainers/upload-release.pl

@@ -55,6 +55,11 @@ my $releaseDir = "nix/$releaseName";
 my $tmpDir = "$TMPDIR/nix-release/$releaseName";
 File::Path::make_path($tmpDir);
 
+my $narCache = "$TMPDIR/nar-cache";
+File::Path::make_path($narCache);
+
+my $binaryCache = "https://cache.nixos.org/?local-nar-cache=$narCache";
+
 # S3 setup.
 my $aws_access_key_id = $ENV{'AWS_ACCESS_KEY_ID'} or die "No AWS_ACCESS_KEY_ID given.";
 my $aws_secret_access_key = $ENV{'AWS_SECRET_ACCESS_KEY'} or die "No AWS_SECRET_ACCESS_KEY given.";
@@ -80,6 +85,7 @@ sub downloadFile {
     my ($jobName, $productNr, $dstName) = @_;
 
     my $buildInfo = decode_json(fetch("$evalUrl/job/$jobName", 'application/json'));
+    #print STDERR "$jobName: ", Dumper($buildInfo), "\n";
 
     my $srcFile = $buildInfo->{buildproducts}->{$productNr}->{path} or die "job '$jobName' lacks product $productNr\n";
     $dstName //= basename($srcFile);
@@ -87,19 +93,27 @@ sub downloadFile {
 
     if (!-e $tmpFile) {
         print STDERR "downloading $srcFile to $tmpFile...\n";
-        system("NIX_REMOTE=https://cache.nixos.org/ nix store cat '$srcFile' > '$tmpFile'") == 0
+
+        my $fileInfo = decode_json(`NIX_REMOTE=$binaryCache nix store ls --json '$srcFile'`);
+
+        $srcFile = $fileInfo->{target} if $fileInfo->{type} eq 'symlink';
+
+        #print STDERR $srcFile, " ", Dumper($fileInfo), "\n";
+
+        system("NIX_REMOTE=$binaryCache nix store cat '$srcFile' > '$tmpFile'.tmp") == 0
             or die "unable to fetch $srcFile\n";
+        rename("$tmpFile.tmp", $tmpFile) or die;
     }
 
-    my $sha256_expected = $buildInfo->{buildproducts}->{$productNr}->{sha256hash} or die;
+    my $sha256_expected = $buildInfo->{buildproducts}->{$productNr}->{sha256hash};
     my $sha256_actual = `nix hash file --base16 --type sha256 '$tmpFile'`;
     chomp $sha256_actual;
-    if ($sha256_expected ne $sha256_actual) {
+    if (defined($sha256_expected) && $sha256_expected ne $sha256_actual) {
         print STDERR "file $tmpFile is corrupt, got $sha256_actual, expected $sha256_expected\n";
         exit 1;
     }
 
-    write_file("$tmpFile.sha256", $sha256_expected);
+    write_file("$tmpFile.sha256", $sha256_actual);
 
     if (! -e "$tmpFile.asc") {
         system("gpg2 --detach-sign --armor $tmpFile") == 0 or die "unable to sign $tmpFile\n";
@@ -117,6 +131,60 @@ downloadFile("binaryTarballCross.x86_64-linux.armv6l-linux", "1");
 downloadFile("binaryTarballCross.x86_64-linux.armv7l-linux", "1");
 downloadFile("installerScript", "1");
 
+# Upload docker images to dockerhub.
+my $dockerManifest = "";
+my $dockerManifestLatest = "";
+
+for my $platforms (["x86_64-linux", "amd64"], ["aarch64-linux", "arm64"]) {
+    my $system = $platforms->[0];
+    my $dockerPlatform = $platforms->[1];
+    my $fn = "nix-$version-docker-image-$dockerPlatform.tar.gz";
+    downloadFile("dockerImage.$system", "1", $fn);
+
+    print STDERR "loading docker image for $dockerPlatform...\n";
+    system("docker load -i $tmpDir/$fn") == 0 or die;
+
+    my $tag = "nixos/nix:$version-$dockerPlatform";
+    my $latestTag = "nixos/nix:latest-$dockerPlatform";
+
+    print STDERR "tagging $version docker image for $dockerPlatform...\n";
+    system("docker tag nix:$version $tag") == 0 or die;
+
+    if ($isLatest) {
+        print STDERR "tagging latest docker image for $dockerPlatform...\n";
+        system("docker tag nix:$version $latestTag") == 0 or die;
+    }
+
+    print STDERR "pushing $version docker image for $dockerPlatform...\n";
+    system("docker push -q $tag") == 0 or die;
+
+    if ($isLatest) {
+        print STDERR "pushing latest docker image for $dockerPlatform...\n";
+        system("docker push -q $latestTag") == 0 or die;
+    }
+
+    $dockerManifest .= " --amend $tag";
+    $dockerManifestLatest .= " --amend $latestTag"
+}
+
+print STDERR "creating multi-platform docker manifest...\n";
+system("docker manifest rm nixos/nix:$version");
+system("docker manifest create nixos/nix:$version $dockerManifest") == 0 or die;
+if ($isLatest) {
+    print STDERR "creating latest multi-platform docker manifest...\n";
+    system("docker manifest rm nixos/nix:latest");
+    system("docker manifest create nixos/nix:latest $dockerManifestLatest") == 0 or die;
+}
+
+print STDERR "pushing multi-platform docker manifest...\n";
+system("docker manifest push nixos/nix:$version") == 0 or die;
+
+if ($isLatest) {
+    print STDERR "pushing latest multi-platform docker manifest...\n";
+    system("docker manifest push nixos/nix:latest") == 0 or die;
+}
+
+# Upload release files to S3.
 for my $fn (glob "$tmpDir/*") {
     my $name = basename($fn);
     my $dstKey = "$releaseDir/" . $name;

misc/bash/completion.sh

@@ -15,7 +15,7 @@ function _complete_nix {
         else
             COMPREPLY+=("$completion")
         fi
-    done < <(NIX_GET_COMPLETIONS=$cword "${words[@]/#\~/$HOME}")
+    done < <(NIX_GET_COMPLETIONS=$cword "${words[@]/#\~/$HOME}" 2>/dev/null)
     __ltrim_colon_completions "$cur"
 }
 

misc/zsh/completion.zsh

@@ -4,7 +4,7 @@ function _nix() {
   local ifs_bk="$IFS"
   local input=("${(Q)words[@]}")
   IFS=$'\n'
-  local res=($(NIX_GET_COMPLETIONS=$((CURRENT - 1)) "$input[@]"))
+  local res=($(NIX_GET_COMPLETIONS=$((CURRENT - 1)) "$input[@]" 2>/dev/null))
   IFS="$ifs_bk"
   local tpe="${${res[1]}%%>	*}"
   local -a suggestions

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-"checksum rand_pcg 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)" = "abf9b09b01790cfe0364f52bf32995ea3c39f4d2dd011eac241d2914146d0b44"
-"checksum rand_xorshift 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cbf7e9e623549b0e21f6e97cf8ecf247c1a8fd2e8a992ae265314300b2455d5c"
-"checksum rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "678054eb77286b51581ba43620cc911abf02758c91f93f479767aed0f90458b2"
-"checksum redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)" = "2439c63f3f6139d1b57529d16bc3b8bb855230c8efcc5d3a896c8bea7c3b1e84"
-"checksum regex-syntax 0.6.12 (registry+https://github.com/rust-lang/crates.io-index)" = "11a7e20d1cce64ef2fed88b66d347f88bd9babb82845b2b858f3edbf59a4f716"
-"checksum remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)" = "4a83fa3702a688b9359eccba92d153ac33fd2e8462f9e0e3fdf155239ea7792e"
-"checksum rusty-fork 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "3dd93264e10c577503e926bd1430193eeb5d21b059148910082245309b424fae"
-"checksum tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6e24d9338a0a5be79593e2fa15a648add6138caa803e2d5bc782c371732ca9"
-"checksum wait-timeout 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9f200f5b12eb75f8c1ed65abd4b2db8a6e1b138a20de009dacee265a2498f3f6"
-"checksum wasi 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b89c3ce4ce14bdc6fb6beaf9ec7928ca331de5df7e5ea278375642a2f478570d"
-"checksum winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)" = "8093091eeb260906a183e6ae1abdba2ef5ef2257a21801128899c3fc699229c6"
-"checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
-"checksum winapi-x86_64-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"

nix-rust/Cargo.toml

@@ -1,23 +0,0 @@
-[package]
-name = "nix-rust"
-version = "0.1.0"
-authors = ["Eelco Dolstra <edolstra@gmail.com>"]
-edition = "2018"
-
-[lib]
-name = "nixrust"
-crate-type = ["cdylib"]
-
-[dependencies]
-libc = "0.2"
-#futures-preview = { version = "=0.3.0-alpha.19" }
-#hyper = "0.13.0-alpha.4"
-#http = "0.1"
-#tokio = { version = "0.2.0-alpha.6", default-features = false, features = ["rt-full"] }
-lazy_static = "1.4"
-#byteorder = "1.3"
-
-[dev-dependencies]
-hex = "0.3"
-assert_matches = "1.3"
-proptest = "0.9"

nix-rust/local.mk

@@ -1,48 +0,0 @@
-ifeq ($(OPTIMIZE), 1)
-  RUST_MODE = --release
-  RUST_DIR = release
-else
-  RUST_MODE =
-  RUST_DIR = debug
-endif
-
-libnixrust_PATH := $(d)/target/$(RUST_DIR)/libnixrust.$(SO_EXT)
-libnixrust_INSTALL_PATH := $(libdir)/libnixrust.$(SO_EXT)
-libnixrust_LDFLAGS_USE := -L$(d)/target/$(RUST_DIR) -lnixrust
-libnixrust_LDFLAGS_USE_INSTALLED := -L$(libdir) -lnixrust
-
-ifdef HOST_LINUX
-libnixrust_LDFLAGS_USE += -ldl
-libnixrust_LDFLAGS_USE_INSTALLED += -ldl
-endif
-
-ifdef HOST_DARWIN
-libnixrust_BUILD_FLAGS = NIX_LDFLAGS="-undefined dynamic_lookup"
-else
-libnixrust_LDFLAGS_USE += -Wl,-rpath,$(abspath $(d)/target/$(RUST_DIR))
-libnixrust_LDFLAGS_USE_INSTALLED += -Wl,-rpath,$(libdir)
-endif
-
-$(libnixrust_PATH): $(call rwildcard, $(d)/src, *.rs) $(d)/Cargo.toml
-	$(trace-gen) cd nix-rust && CARGO_HOME=$$(if [[ -d vendor ]]; then echo vendor; fi) \
-	$(libnixrust_BUILD_FLAGS) \
-	  cargo build $(RUST_MODE) $$(if [[ -d vendor ]]; then echo --offline; fi) \
-	&& touch target/$(RUST_DIR)/libnixrust.$(SO_EXT)
-
-$(libnixrust_INSTALL_PATH): $(libnixrust_PATH)
-	$(target-gen) cp $^ $@
-ifdef HOST_DARWIN
-	install_name_tool -id $@ $@
-endif
-
-clean: clean-rust
-
-clean-rust:
-	$(suppress) rm -rfv nix-rust/target
-
-ifndef HOST_DARWIN
-check: rust-tests
-
-rust-tests:
-	$(trace-test) cd nix-rust && CARGO_HOME=$$(if [[ -d vendor ]]; then echo vendor; fi) cargo test --release $$(if [[ -d vendor ]]; then echo --offline; fi)
-endif

nix-rust/src/c.rs

@@ -1,77 +0,0 @@
-use super::{error, store::path, store::StorePath, util};
-
-#[no_mangle]
-pub unsafe extern "C" fn ffi_String_new(s: &str, out: *mut String) {
-    // FIXME: check whether 's' is valid UTF-8?
-    out.write(s.to_string())
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn ffi_String_drop(self_: *mut String) {
-    std::ptr::drop_in_place(self_);
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_new(
-    path: &str,
-    store_dir: &str,
-) -> Result<StorePath, error::CppException> {
-    StorePath::new(std::path::Path::new(path), std::path::Path::new(store_dir))
-        .map_err(|err| err.into())
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_new2(
-    hash: &[u8; crate::store::path::STORE_PATH_HASH_BYTES],
-    name: &str,
-) -> Result<StorePath, error::CppException> {
-    StorePath::from_parts(*hash, name).map_err(|err| err.into())
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_fromBaseName(
-    base_name: &str,
-) -> Result<StorePath, error::CppException> {
-    StorePath::new_from_base_name(base_name).map_err(|err| err.into())
-}
-
-#[no_mangle]
-pub unsafe extern "C" fn ffi_StorePath_drop(self_: *mut StorePath) {
-    std::ptr::drop_in_place(self_);
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_to_string(self_: &StorePath) -> Vec<u8> {
-    let mut buf = vec![0; path::STORE_PATH_HASH_CHARS + 1 + self_.name.name().len()];
-    util::base32::encode_into(self_.hash.hash(), &mut buf[0..path::STORE_PATH_HASH_CHARS]);
-    buf[path::STORE_PATH_HASH_CHARS] = b'-';
-    buf[path::STORE_PATH_HASH_CHARS + 1..].clone_from_slice(self_.name.name().as_bytes());
-    buf
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_less_than(a: &StorePath, b: &StorePath) -> bool {
-    a < b
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_eq(a: &StorePath, b: &StorePath) -> bool {
-    a == b
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_clone(self_: &StorePath) -> StorePath {
-    self_.clone()
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_name(self_: &StorePath) -> &str {
-    self_.name.name()
-}
-
-#[no_mangle]
-pub extern "C" fn ffi_StorePath_hash_data(
-    self_: &StorePath,
-) -> &[u8; crate::store::path::STORE_PATH_HASH_BYTES] {
-    self_.hash.hash()
-}

nix-rust/src/error.rs

@@ -1,118 +0,0 @@
-use std::fmt;
-
-#[derive(Debug)]
-pub enum Error {
-    InvalidPath(crate::store::StorePath),
-    BadStorePath(std::path::PathBuf),
-    NotInStore(std::path::PathBuf),
-    BadNarInfo,
-    BadBase32,
-    StorePathNameEmpty,
-    StorePathNameTooLong,
-    BadStorePathName,
-    NarSizeFieldTooBig,
-    BadNarString,
-    BadNarPadding,
-    BadNarVersionMagic,
-    MissingNarOpenTag,
-    MissingNarCloseTag,
-    MissingNarField,
-    BadNarField(String),
-    BadExecutableField,
-    IOError(std::io::Error),
-    #[cfg(unused)]
-    HttpError(hyper::error::Error),
-    Misc(String),
-    #[cfg(not(test))]
-    Foreign(CppException),
-    BadTarFileMemberName(String),
-}
-
-impl From<std::io::Error> for Error {
-    fn from(err: std::io::Error) -> Self {
-        Error::IOError(err)
-    }
-}
-
-#[cfg(unused)]
-impl From<hyper::error::Error> for Error {
-    fn from(err: hyper::error::Error) -> Self {
-        Error::HttpError(err)
-    }
-}
-
-impl fmt::Display for Error {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Error::InvalidPath(_) => write!(f, "invalid path"),
-            Error::BadNarInfo => write!(f, ".narinfo file is corrupt"),
-            Error::BadStorePath(path) => write!(f, "path '{}' is not a store path", path.display()),
-            Error::NotInStore(path) => {
-                write!(f, "path '{}' is not in the Nix store", path.display())
-            }
-            Error::BadBase32 => write!(f, "invalid base32 string"),
-            Error::StorePathNameEmpty => write!(f, "store path name is empty"),
-            Error::StorePathNameTooLong => {
-                write!(f, "store path name is longer than 211 characters")
-            }
-            Error::BadStorePathName => write!(f, "store path name contains forbidden character"),
-            Error::NarSizeFieldTooBig => write!(f, "size field in NAR is too big"),
-            Error::BadNarString => write!(f, "NAR string is not valid UTF-8"),
-            Error::BadNarPadding => write!(f, "NAR padding is not zero"),
-            Error::BadNarVersionMagic => write!(f, "unsupported NAR version"),
-            Error::MissingNarOpenTag => write!(f, "NAR open tag is missing"),
-            Error::MissingNarCloseTag => write!(f, "NAR close tag is missing"),
-            Error::MissingNarField => write!(f, "expected NAR field is missing"),
-            Error::BadNarField(s) => write!(f, "unrecognized NAR field '{}'", s),
-            Error::BadExecutableField => write!(f, "bad 'executable' field in NAR"),
-            Error::IOError(err) => write!(f, "I/O error: {}", err),
-            #[cfg(unused)]
-            Error::HttpError(err) => write!(f, "HTTP error: {}", err),
-            #[cfg(not(test))]
-            Error::Foreign(_) => write!(f, "<C++ exception>"), // FIXME
-            Error::Misc(s) => write!(f, "{}", s),
-            Error::BadTarFileMemberName(s) => {
-                write!(f, "tar archive contains illegal file name '{}'", s)
-            }
-        }
-    }
-}
-
-#[cfg(not(test))]
-impl From<Error> for CppException {
-    fn from(err: Error) -> Self {
-        match err {
-            Error::Foreign(ex) => ex,
-            _ => CppException::new(&err.to_string()),
-        }
-    }
-}
-
-#[cfg(not(test))]
-#[repr(C)]
-#[derive(Debug)]
-pub struct CppException(*const libc::c_void); // == std::exception_ptr*
-
-#[cfg(not(test))]
-impl CppException {
-    fn new(s: &str) -> Self {
-        Self(unsafe { make_error(s) })
-    }
-}
-
-#[cfg(not(test))]
-impl Drop for CppException {
-    fn drop(&mut self) {
-        unsafe {
-            destroy_error(self.0);
-        }
-    }
-}
-
-#[cfg(not(test))]
-extern "C" {
-    #[allow(improper_ctypes)] // YOLO
-    fn make_error(s: &str) -> *const libc::c_void;
-
-    fn destroy_error(exc: *const libc::c_void);
-}

nix-rust/src/lib.rs

@@ -1,10 +0,0 @@
-#[allow(improper_ctypes_definitions)]
-#[cfg(not(test))]
-mod c;
-mod error;
-#[cfg(unused)]
-mod nar;
-mod store;
-mod util;
-
-pub use error::Error;

nix-rust/src/nar.rs

@@ -1,126 +0,0 @@
-use crate::Error;
-use byteorder::{LittleEndian, ReadBytesExt};
-use std::convert::TryFrom;
-use std::io::Read;
-
-pub fn parse<R: Read>(input: &mut R) -> Result<(), Error> {
-    if String::read(input)? != NAR_VERSION_MAGIC {
-        return Err(Error::BadNarVersionMagic);
-    }
-
-    parse_file(input)
-}
-
-const NAR_VERSION_MAGIC: &str = "nix-archive-1";
-
-fn parse_file<R: Read>(input: &mut R) -> Result<(), Error> {
-    if String::read(input)? != "(" {
-        return Err(Error::MissingNarOpenTag);
-    }
-
-    if String::read(input)? != "type" {
-        return Err(Error::MissingNarField);
-    }
-
-    match String::read(input)?.as_ref() {
-        "regular" => {
-            let mut _executable = false;
-            let mut tag = String::read(input)?;
-            if tag == "executable" {
-                _executable = true;
-                if String::read(input)? != "" {
-                    return Err(Error::BadExecutableField);
-                }
-                tag = String::read(input)?;
-            }
-            if tag != "contents" {
-                return Err(Error::MissingNarField);
-            }
-            let _contents = Vec::<u8>::read(input)?;
-            if String::read(input)? != ")" {
-                return Err(Error::MissingNarCloseTag);
-            }
-        }
-        "directory" => loop {
-            match String::read(input)?.as_ref() {
-                "entry" => {
-                    if String::read(input)? != "(" {
-                        return Err(Error::MissingNarOpenTag);
-                    }
-                    if String::read(input)? != "name" {
-                        return Err(Error::MissingNarField);
-                    }
-                    let _name = String::read(input)?;
-                    if String::read(input)? != "node" {
-                        return Err(Error::MissingNarField);
-                    }
-                    parse_file(input)?;
-                    let tag = String::read(input)?;
-                    if tag != ")" {
-                        return Err(Error::MissingNarCloseTag);
-                    }
-                }
-                ")" => break,
-                s => return Err(Error::BadNarField(s.into())),
-            }
-        },
-        "symlink" => {
-            if String::read(input)? != "target" {
-                return Err(Error::MissingNarField);
-            }
-            let _target = String::read(input)?;
-            if String::read(input)? != ")" {
-                return Err(Error::MissingNarCloseTag);
-            }
-        }
-        s => return Err(Error::BadNarField(s.into())),
-    }
-
-    Ok(())
-}
-
-trait Deserialize: Sized {
-    fn read<R: Read>(input: &mut R) -> Result<Self, Error>;
-}
-
-impl Deserialize for String {
-    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
-        let buf = Deserialize::read(input)?;
-        Ok(String::from_utf8(buf).map_err(|_| Error::BadNarString)?)
-    }
-}
-
-impl Deserialize for Vec<u8> {
-    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
-        let n: usize = Deserialize::read(input)?;
-        let mut buf = vec![0; n];
-        input.read_exact(&mut buf)?;
-        skip_padding(input, n)?;
-        Ok(buf)
-    }
-}
-
-fn skip_padding<R: Read>(input: &mut R, len: usize) -> Result<(), Error> {
-    if len % 8 != 0 {
-        let mut buf = [0; 8];
-        let buf = &mut buf[0..8 - (len % 8)];
-        input.read_exact(buf)?;
-        if !buf.iter().all(|b| *b == 0) {
-            return Err(Error::BadNarPadding);
-        }
-    }
-    Ok(())
-}
-
-impl Deserialize for u64 {
-    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
-        Ok(input.read_u64::<LittleEndian>()?)
-    }
-}
-
-impl Deserialize for usize {
-    fn read<R: Read>(input: &mut R) -> Result<Self, Error> {
-        let n: u64 = Deserialize::read(input)?;
-        Ok(usize::try_from(n).map_err(|_| Error::NarSizeFieldTooBig)?)
-    }
-}

nix-rust/src/store/binary_cache_store.rs

@@ -1,48 +0,0 @@
-use super::{PathInfo, Store, StorePath};
-use crate::Error;
-use hyper::client::Client;
-
-pub struct BinaryCacheStore {
-    base_uri: String,
-    client: Client<hyper::client::HttpConnector, hyper::Body>,
-}
-
-impl BinaryCacheStore {
-    pub fn new(base_uri: String) -> Self {
-        Self {
-            base_uri,
-            client: Client::new(),
-        }
-    }
-}
-
-impl Store for BinaryCacheStore {
-    fn query_path_info(
-        &self,
-        path: &StorePath,
-    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<PathInfo, Error>> + Send>> {
-        let uri = format!("{}/{}.narinfo", self.base_uri.clone(), path.hash);
-        let path = path.clone();
-        let client = self.client.clone();
-        let store_dir = self.store_dir().to_string();
-
-        Box::pin(async move {
-            let response = client.get(uri.parse::<hyper::Uri>().unwrap()).await?;
-
-            if response.status() == hyper::StatusCode::NOT_FOUND
-                || response.status() == hyper::StatusCode::FORBIDDEN
-            {
-                return Err(Error::InvalidPath(path));
-            }
-
-            let mut body = response.into_body();
-
-            let mut bytes = Vec::new();
-            while let Some(next) = body.next().await {
-                bytes.extend(next?);
-            }
-
-            PathInfo::parse_nar_info(std::str::from_utf8(&bytes).unwrap(), &store_dir)
-        })
-    }
-}

nix-rust/src/store/mod.rs

@@ -1,17 +0,0 @@
-pub mod path;
-
-#[cfg(unused)]
-mod binary_cache_store;
-#[cfg(unused)]
-mod path_info;
-#[cfg(unused)]
-mod store;
-
-pub use path::{StorePath, StorePathHash, StorePathName};
-
-#[cfg(unused)]
-pub use binary_cache_store::BinaryCacheStore;
-#[cfg(unused)]
-pub use path_info::PathInfo;
-#[cfg(unused)]
-pub use store::Store;

nix-rust/src/store/path.rs

@@ -1,224 +0,0 @@
-use crate::error::Error;
-use crate::util::base32;
-use std::fmt;
-use std::path::Path;
-
-#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
-pub struct StorePath {
-    pub hash: StorePathHash,
-    pub name: StorePathName,
-}
-
-pub const STORE_PATH_HASH_BYTES: usize = 20;
-pub const STORE_PATH_HASH_CHARS: usize = 32;
-
-impl StorePath {
-    pub fn new(path: &Path, store_dir: &Path) -> Result<Self, Error> {
-        if path.parent() != Some(store_dir) {
-            return Err(Error::NotInStore(path.into()));
-        }
-        Self::new_from_base_name(
-            path.file_name()
-                .ok_or_else(|| Error::BadStorePath(path.into()))?
-                .to_str()
-                .ok_or_else(|| Error::BadStorePath(path.into()))?,
-        )
-    }
-
-    pub fn from_parts(hash: [u8; STORE_PATH_HASH_BYTES], name: &str) -> Result<Self, Error> {
-        Ok(StorePath {
-            hash: StorePathHash(hash),
-            name: StorePathName::new(name)?,
-        })
-    }
-
-    pub fn new_from_base_name(base_name: &str) -> Result<Self, Error> {
-        if base_name.len() < STORE_PATH_HASH_CHARS + 1
-            || base_name.as_bytes()[STORE_PATH_HASH_CHARS] != b'-'
-        {
-            return Err(Error::BadStorePath(base_name.into()));
-        }
-
-        Ok(StorePath {
-            hash: StorePathHash::new(&base_name[0..STORE_PATH_HASH_CHARS])?,
-            name: StorePathName::new(&base_name[STORE_PATH_HASH_CHARS + 1..])?,
-        })
-    }
-}
-
-impl fmt::Display for StorePath {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        write!(f, "{}-{}", self.hash, self.name)
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub struct StorePathHash([u8; STORE_PATH_HASH_BYTES]);
-
-impl StorePathHash {
-    pub fn new(s: &str) -> Result<Self, Error> {
-        assert_eq!(s.len(), STORE_PATH_HASH_CHARS);
-        let v = base32::decode(s)?;
-        assert_eq!(v.len(), STORE_PATH_HASH_BYTES);
-        let mut bytes: [u8; 20] = Default::default();
-        bytes.copy_from_slice(&v[0..STORE_PATH_HASH_BYTES]);
-        Ok(Self(bytes))
-    }
-
-    pub fn hash(&self) -> &[u8; STORE_PATH_HASH_BYTES] {
-        &self.0
-    }
-}
-
-impl fmt::Display for StorePathHash {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let mut buf = vec![0; STORE_PATH_HASH_CHARS];
-        base32::encode_into(&self.0, &mut buf);
-        f.write_str(std::str::from_utf8(&buf).unwrap())
-    }
-}
-
-impl Ord for StorePathHash {
-    fn cmp(&self, other: &Self) -> std::cmp::Ordering {
-        // Historically we've sorted store paths by their base32
-        // serialization, but our base32 encodes bytes in reverse
-        // order. So compare them in reverse order as well.
-        self.0.iter().rev().cmp(other.0.iter().rev())
-    }
-}
-
-impl PartialOrd for StorePathHash {
-    fn partial_cmp(&self, other: &Self) -> Option<std::cmp::Ordering> {
-        Some(self.cmp(other))
-    }
-}
-
-#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Debug)]
-pub struct StorePathName(String);
-
-impl StorePathName {
-    pub fn new(s: &str) -> Result<Self, Error> {
-        if s.is_empty() {
-            return Err(Error::StorePathNameEmpty);
-        }
-
-        if s.len() > 211 {
-            return Err(Error::StorePathNameTooLong);
-        }
-
-        let is_good_path_name = s.chars().all(|c| {
-            c.is_ascii_alphabetic()
-                || c.is_ascii_digit()
-                || c == '+'
-                || c == '-'
-                || c == '.'
-                || c == '_'
-                || c == '?'
-                || c == '='
-        });
-        if s.starts_with('.') || !is_good_path_name {
-            return Err(Error::BadStorePathName);
-        }
-
-        Ok(Self(s.to_string()))
-    }
-
-    pub fn name(&self) -> &str {
-        &self.0
-    }
-}
-
-impl fmt::Display for StorePathName {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str(&self.0)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use assert_matches::assert_matches;
-
-    #[test]
-    fn test_parse() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-konsole-18.12.3";
-        let p = StorePath::new_from_base_name(&s).unwrap();
-        assert_eq!(p.name.0, "konsole-18.12.3");
-        assert_eq!(
-            p.hash.0,
-            [
-                0x9f, 0x76, 0x49, 0x20, 0xf6, 0x5d, 0xe9, 0x71, 0xc4, 0xca, 0x46, 0x21, 0xab, 0xff,
-                0x9b, 0x44, 0xef, 0x87, 0x0f, 0x3c
-            ]
-        );
-    }
-
-    #[test]
-    fn test_no_name() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::StorePathNameEmpty)
-        );
-    }
-
-    #[test]
-    fn test_no_dash() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::BadStorePath(_))
-        );
-    }
-
-    #[test]
-    fn test_short_hash() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxl-konsole-18.12.3";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::BadStorePath(_))
-        );
-    }
-
-    #[test]
-    fn test_invalid_hash() {
-        let s = "7h7qgvs4kgzsn8e6rb273saxyqh4jxlz-konsole-18.12.3";
-        assert_matches!(StorePath::new_from_base_name(&s), Err(Error::BadBase32));
-    }
-
-    #[test]
-    fn test_long_name() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
-        assert_matches!(StorePath::new_from_base_name(&s), Ok(_));
-    }
-
-    #[test]
-    fn test_too_long_name() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::StorePathNameTooLong)
-        );
-    }
-
-    #[test]
-    fn test_bad_name() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-foo bar";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::BadStorePathName)
-        );
-
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-kónsole";
-        assert_matches!(
-            StorePath::new_from_base_name(&s),
-            Err(Error::BadStorePathName)
-        );
-    }
-
-    #[test]
-    fn test_roundtrip() {
-        let s = "7h7qgvs4kgzsn8a6rb273saxyqh4jxlz-konsole-18.12.3";
-        assert_eq!(StorePath::new_from_base_name(&s).unwrap().to_string(), s);
-    }
-}

nix-rust/src/store/path_info.rs

@@ -1,70 +0,0 @@
-use crate::store::StorePath;
-use crate::Error;
-use std::collections::BTreeSet;
-
-#[derive(Clone, Debug)]
-pub struct PathInfo {
-    pub path: StorePath,
-    pub references: BTreeSet<StorePath>,
-    pub nar_size: u64,
-    pub deriver: Option<StorePath>,
-
-    // Additional binary cache info.
-    pub url: Option<String>,
-    pub compression: Option<String>,
-    pub file_size: Option<u64>,
-}
-
-impl PathInfo {
-    pub fn parse_nar_info(nar_info: &str, store_dir: &str) -> Result<Self, Error> {
-        let mut path = None;
-        let mut references = BTreeSet::new();
-        let mut nar_size = None;
-        let mut deriver = None;
-        let mut url = None;
-        let mut compression = None;
-        let mut file_size = None;
-
-        for line in nar_info.lines() {
-            let colon = line.find(':').ok_or(Error::BadNarInfo)?;
-
-            let (name, value) = line.split_at(colon);
-
-            if !value.starts_with(": ") {
-                return Err(Error::BadNarInfo);
-            }
-
-            let value = &value[2..];
-
-            if name == "StorePath" {
-                path = Some(StorePath::new(std::path::Path::new(value), store_dir)?);
-            } else if name == "NarSize" {
-                nar_size = Some(u64::from_str_radix(value, 10).map_err(|_| Error::BadNarInfo)?);
-            } else if name == "References" {
-                if !value.is_empty() {
-                    for r in value.split(' ') {
-                        references.insert(StorePath::new_from_base_name(r)?);
-                    }
-                }
-            } else if name == "Deriver" {
-                deriver = Some(StorePath::new_from_base_name(value)?);
-            } else if name == "URL" {
-                url = Some(value.into());
-            } else if name == "Compression" {
-                compression = Some(value.into());
-            } else if name == "FileSize" {
-                file_size = Some(u64::from_str_radix(value, 10).map_err(|_| Error::BadNarInfo)?);
-            }
-        }
-
-        Ok(PathInfo {
-            path: path.ok_or(Error::BadNarInfo)?,
-            references,
-            nar_size: nar_size.ok_or(Error::BadNarInfo)?,
-            deriver,
-            url: Some(url.ok_or(Error::BadNarInfo)?),
-            compression,
-            file_size,
-        })
-    }
-}

nix-rust/src/store/store.rs

@@ -1,53 +0,0 @@
-use super::{PathInfo, StorePath};
-use crate::Error;
-use std::collections::{BTreeMap, BTreeSet};
-use std::path::Path;
-
-pub trait Store: Send + Sync {
-    fn store_dir(&self) -> &str {
-        "/nix/store"
-    }
-
-    fn query_path_info(
-        &self,
-        store_path: &StorePath,
-    ) -> std::pin::Pin<Box<dyn std::future::Future<Output = Result<PathInfo, Error>> + Send>>;
-}
-
-impl dyn Store {
-    pub fn parse_store_path(&self, path: &Path) -> Result<StorePath, Error> {
-        StorePath::new(path, self.store_dir())
-    }
-
-    pub async fn compute_path_closure(
-        &self,
-        roots: BTreeSet<StorePath>,
-    ) -> Result<BTreeMap<StorePath, PathInfo>, Error> {
-        let mut done = BTreeSet::new();
-        let mut result = BTreeMap::new();
-        let mut pending = vec![];
-
-        for root in roots {
-            pending.push(self.query_path_info(&root));
-            done.insert(root);
-        }
-
-        while !pending.is_empty() {
-            let (info, _, remaining) = futures::future::select_all(pending).await;
-            pending = remaining;
-
-            let info = info?;
-
-            for path in &info.references {
-                if !done.contains(path) {
-                    pending.push(self.query_path_info(&path));
-                    done.insert(path.clone());
-                }
-            }
-
-            result.insert(info.path.clone(), info);
-        }
-
-        Ok(result)
-    }
-}

nix-rust/src/util/base32.rs

@@ -1,160 +0,0 @@
-use crate::error::Error;
-use lazy_static::lazy_static;
-
-pub fn encoded_len(input_len: usize) -> usize {
-    if input_len == 0 {
-        0
-    } else {
-        (input_len * 8 - 1) / 5 + 1
-    }
-}
-
-pub fn decoded_len(input_len: usize) -> usize {
-    input_len * 5 / 8
-}
-
-static BASE32_CHARS: &[u8; 32] = &b"0123456789abcdfghijklmnpqrsvwxyz";
-
-lazy_static! {
-    static ref BASE32_CHARS_REVERSE: Box<[u8; 256]> = {
-        let mut xs = [0xffu8; 256];
-        for (n, c) in BASE32_CHARS.iter().enumerate() {
-            xs[*c as usize] = n as u8;
-        }
-        Box::new(xs)
-    };
-}
-
-pub fn encode(input: &[u8]) -> String {
-    let mut buf = vec![0; encoded_len(input.len())];
-    encode_into(input, &mut buf);
-    std::str::from_utf8(&buf).unwrap().to_string()
-}
-
-pub fn encode_into(input: &[u8], output: &mut [u8]) {
-    let len = encoded_len(input.len());
-    assert_eq!(len, output.len());
-
-    let mut nr_bits_left: usize = 0;
-    let mut bits_left: u16 = 0;
-    let mut pos = len;
-
-    for b in input {
-        bits_left |= (*b as u16) << nr_bits_left;
-        nr_bits_left += 8;
-        while nr_bits_left > 5 {
-            output[pos - 1] = BASE32_CHARS[(bits_left & 0x1f) as usize];
-            pos -= 1;
-            bits_left >>= 5;
-            nr_bits_left -= 5;
-        }
-    }
-
-    if nr_bits_left > 0 {
-        output[pos - 1] = BASE32_CHARS[(bits_left & 0x1f) as usize];
-        pos -= 1;
-    }
-
-    assert_eq!(pos, 0);
-}
-
-pub fn decode(input: &str) -> Result<Vec<u8>, crate::Error> {
-    let mut res = Vec::with_capacity(decoded_len(input.len()));
-
-    let mut nr_bits_left: usize = 0;
-    let mut bits_left: u16 = 0;
-
-    for c in input.chars().rev() {
-        let b = BASE32_CHARS_REVERSE[c as usize];
-        if b == 0xff {
-            return Err(Error::BadBase32);
-        }
-        bits_left |= (b as u16) << nr_bits_left;
-        nr_bits_left += 5;
-        if nr_bits_left >= 8 {
-            res.push((bits_left & 0xff) as u8);
-            bits_left >>= 8;
-            nr_bits_left -= 8;
-        }
-    }
-
-    if nr_bits_left > 0 && bits_left != 0 {
-        return Err(Error::BadBase32);
-    }
-
-    Ok(res)
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use assert_matches::assert_matches;
-    use hex;
-    use proptest::proptest;
-
-    #[test]
-    fn test_encode() {
-        assert_eq!(encode(&[]), "");
-
-        assert_eq!(
-            encode(&hex::decode("0839703786356bca59b0f4a32987eb2e6de43ae8").unwrap()),
-            "x0xf8v9fxf3jk8zln1cwlsrmhqvp0f88"
-        );
-
-        assert_eq!(
-            encode(
-                &hex::decode("ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad")
-                    .unwrap()
-            ),
-            "1b8m03r63zqhnjf7l5wnldhh7c134ap5vpj0850ymkq1iyzicy5s"
-        );
-
-        assert_eq!(
-            encode(
-                &hex::decode("ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f")
-                    .unwrap()
-            ),
-            "2gs8k559z4rlahfx0y688s49m2vvszylcikrfinm30ly9rak69236nkam5ydvly1ai7xac99vxfc4ii84hawjbk876blyk1jfhkbbyx"
-        );
-    }
-
-    #[test]
-    fn test_decode() {
-        assert_eq!(hex::encode(decode("").unwrap()), "");
-
-        assert_eq!(
-            hex::encode(decode("x0xf8v9fxf3jk8zln1cwlsrmhqvp0f88").unwrap()),
-            "0839703786356bca59b0f4a32987eb2e6de43ae8"
-        );
-
-        assert_eq!(
-            hex::encode(decode("1b8m03r63zqhnjf7l5wnldhh7c134ap5vpj0850ymkq1iyzicy5s").unwrap()),
-            "ba7816bf8f01cfea414140de5dae2223b00361a396177a9cb410ff61f20015ad"
-        );
-
-        assert_eq!(
-            hex::encode(decode("2gs8k559z4rlahfx0y688s49m2vvszylcikrfinm30ly9rak69236nkam5ydvly1ai7xac99vxfc4ii84hawjbk876blyk1jfhkbbyx").unwrap()),
-            "ddaf35a193617abacc417349ae20413112e6fa4e89a97ea20a9eeee64b55d39a2192992a274fc1a836ba3c23a3feebbd454d4423643ce80e2a9ac94fa54ca49f"
-        );
-
-        assert_matches!(
-            decode("xoxf8v9fxf3jk8zln1cwlsrmhqvp0f88"),
-            Err(Error::BadBase32)
-        );
-        assert_matches!(
-            decode("2b8m03r63zqhnjf7l5wnldhh7c134ap5vpj0850ymkq1iyzicy5s"),
-            Err(Error::BadBase32)
-        );
-        assert_matches!(decode("2"), Err(Error::BadBase32));
-        assert_matches!(decode("2gs"), Err(Error::BadBase32));
-        assert_matches!(decode("2gs8"), Err(Error::BadBase32));
-    }
-
-    proptest! {
-
-        #[test]
-        fn roundtrip(s: Vec<u8>) {
-            assert_eq!(s, decode(&encode(&s)).unwrap());
-        }
-    }
-}

nix-rust/src/util/mod.rs

@@ -1 +0,0 @@
-pub mod base32;

perl/lib/Nix/Store.xs

@@ -240,7 +240,7 @@ SV * convertHash(char * algo, char * s, int toBase32)
     PPCODE:
         try {
             auto h = Hash::parseAny(s, parseHashType(algo));
-            string s = h.to_string(toBase32 ? Base32 : Base16, false);
+            auto s = h.to_string(toBase32 ? Base32 : Base16, false);
             XPUSHs(sv_2mortal(newSVpv(s.c_str(), 0)));
         } catch (Error & e) {
             croak("%s", e.what());

scripts/check-hydra-status.sh

@@ -16,12 +16,17 @@ someBuildFailed=0
 for buildId in $BUILDS_FOR_LATEST_EVAL; do
   buildInfo=$(curl -sS -H 'Accept: application/json' "https://hydra.nixos.org/build/$buildId")
 
-  buildStatus=$(echo "$buildInfo" | \
-    jq -r '.buildstatus')
+  finished=$(echo "$buildInfo" | jq -r '.finished')
 
-  if [[ "$buildStatus" -ne 0 ]]; then
+  if [[ $finished = 0 ]]; then
+    continue
+  fi
+
+  buildStatus=$(echo "$buildInfo" | jq -r '.buildstatus')
+
+  if [[ $buildStatus != 0 ]]; then
     someBuildFailed=1
-    echo "Job “$(echo "$buildInfo" | jq -r '.job')” failed on hydra"
+    echo "Job “$(echo "$buildInfo" | jq -r '.job')” failed on hydra: $buildInfo"
   fi
 done
 

scripts/install-multi-user.sh

@@ -576,21 +576,40 @@ create_directories() {
         # since this bit is cross-platform:
         # - first try with `command -vp` to try and find
         #   chown in the usual places
+        #   * to work around some sort of deficiency in
+        #     `command -p` in macOS bash 3.2, we also add
+        #     PATH="$(getconf PATH 2>/dev/null)". As long as
+        #     getconf is found, this should set a sane PATH
+        #     which `command -p` in bash 3.2 appears to use.
+        #     A bash with a properly-working `command -p`
+        #     should ignore this hard-set PATH in favor of
+        #     whatever it obtains internally. See
+        #     github.com/NixOS/nix/issues/5768
         # - fall back on `command -v` which would find
         #   any chown on path
         # if we don't find one, the command is already
         # hiding behind || true, and the general state
         # should be one the user can repair once they
         # figure out where chown is...
-        local get_chr_own="$(command -vp chown)"
+        local get_chr_own="$(PATH="$(getconf PATH 2>/dev/null)" command -vp chown)"
         if [[ -z "$get_chr_own" ]]; then
             get_chr_own="$(command -v chown)"
         fi
+
+        if [[ -z "$get_chr_own" ]]; then
+            reminder <<EOF
+I wanted to take root ownership of existing Nix store files,
+but I couldn't locate 'chown'. (You may need to fix your PATH.)
+To manually change file ownership, you can run:
+    sudo chown -R 'root:$NIX_BUILD_GROUP_NAME' '$NIX_ROOT'
+EOF
+        else
             _sudo "to take root ownership of existing Nix store files" \
                   "$get_chr_own" -R "root:$NIX_BUILD_GROUP_NAME" "$NIX_ROOT" || true
         fi
+    fi
     _sudo "to make the basic directory structure of Nix (part 1)" \
-          install -dv -m 0755 /nix /nix/var /nix/var/log /nix/var/log/nix /nix/var/log/nix/drvs /nix/var/nix{,/db,/gcroots,/profiles,/temproots,/userpool} /nix/var/nix/{gcroots,profiles}/per-user
+          install -dv -m 0755 /nix /nix/var /nix/var/log /nix/var/log/nix /nix/var/log/nix/drvs /nix/var/nix{,/db,/gcroots,/profiles,/temproots,/userpool,/daemon-socket} /nix/var/nix/{gcroots,profiles}/per-user
 
     _sudo "to make the basic directory structure of Nix (part 2)" \
           install -dv -g "$NIX_BUILD_GROUP_NAME" -m 1775 /nix/store

scripts/nix-profile.sh.in

@@ -24,6 +24,9 @@ if [ -n "$HOME" ] && [ -n "$USER" ]; then
         export NIX_SSL_CERT_FILE="$NIX_LINK/etc/ca-bundle.crt"
     fi
 
+    # Only use MANPATH if it is already set. In general `man` will just simply
+    # pick up `.nix-profile/share/man` because is it close to `.nix-profile/bin`
+    # which is in the $PATH. For more info, run `manpath -d`.
     if [ -n "${MANPATH-}" ]; then
         export MANPATH="$NIX_LINK/share/man:$MANPATH"
     fi

shell.nix

@@ -1,3 +1,3 @@
-(import (fetchTarball https://github.com/edolstra/flake-compat/archive/master.tar.gz) {
+(import (fetchTarball "https://github.com/edolstra/flake-compat/archive/master.tar.gz") {
   src = ./.;
 }).shellNix

src/build-remote/build-remote.cc

@@ -32,7 +32,7 @@ std::string escapeUri(std::string uri)
     return uri;
 }
 
-static string currentLoad;
+static std::string currentLoad;
 
 static AutoCloseFD openSlotLock(const Machine & m, uint64_t slot)
 {
@@ -97,7 +97,7 @@ static int main_build_remote(int argc, char * * argv)
         }
 
         std::optional<StorePath> drvPath;
-        string storeUri;
+        std::string storeUri;
 
         while (true) {
 
@@ -183,7 +183,7 @@ static int main_build_remote(int argc, char * * argv)
                     else
                     {
                         // build the hint template.
-                        string errorText =
+                        std::string errorText =
                             "Failed to find a machine for remote build!\n"
                             "derivation: %s\nrequired (system, features): (%s, %s)";
                         errorText += "\n%s available machines:";
@@ -193,7 +193,7 @@ static int main_build_remote(int argc, char * * argv)
                             errorText += "\n(%s, %s, %s, %s)";
 
                         // add the template values.
-                        string drvstr;
+                        std::string drvstr;
                         if (drvPath.has_value())
                             drvstr = drvPath->to_string();
                         else
@@ -208,7 +208,7 @@ static int main_build_remote(int argc, char * * argv)
 
                         for (auto & m : machines)
                             error
-                                % concatStringsSep<vector<string>>(", ", m.systemTypes)
+                                % concatStringsSep<std::vector<std::string>>(", ", m.systemTypes)
                                 % m.maxJobs
                                 % concatStringsSep<StringSet>(", ", m.supportedFeatures)
                                 % concatStringsSep<StringSet>(", ", m.mandatoryFeatures);

src/libcmd/command.cc

@@ -54,6 +54,36 @@ void StoreCommand::run()
     run(getStore());
 }
 
+CopyCommand::CopyCommand()
+{
+    addFlag({
+        .longName = "from",
+        .description = "URL of the source Nix store.",
+        .labels = {"store-uri"},
+        .handler = {&srcUri},
+    });
+
+    addFlag({
+        .longName = "to",
+        .description = "URL of the destination Nix store.",
+        .labels = {"store-uri"},
+        .handler = {&dstUri},
+    });
+}
+
+ref<Store> CopyCommand::createStore()
+{
+    return srcUri.empty() ? StoreCommand::createStore() : openStore(srcUri);
+}
+
+ref<Store> CopyCommand::getDstStore()
+{
+    if (srcUri.empty() && dstUri.empty())
+        throw UsageError("you must pass '--from' and/or '--to'");
+
+    return dstUri.empty() ? openStore() : openStore(dstUri);
+}
+
 EvalCommand::EvalCommand()
 {
 }
@@ -73,13 +103,16 @@ ref<Store> EvalCommand::getEvalStore()
 
 ref<EvalState> EvalCommand::getEvalState()
 {
-    if (!evalState) evalState =
+    if (!evalState)
+        evalState =
             #if HAVE_BOEHMGC
             std::allocate_shared<EvalState>(traceable_allocator<EvalState>(),
+                searchPath, getEvalStore(), getStore())
             #else
             std::make_shared<EvalState>(
+                searchPath, getEvalStore(), getStore())
             #endif
-            searchPath, getEvalStore(), getStore());
+            ;
     return ref<EvalState>(evalState);
 }
 

src/libcmd/command.hh

@@ -43,6 +43,19 @@ private:
     std::shared_ptr<Store> _store;
 };
 
+/* A command that copies something between `--from` and `--to`
+   stores. */
+struct CopyCommand : virtual StoreCommand
+{
+    std::string srcUri, dstUri;
+
+    CopyCommand();
+
+    ref<Store> createStore() override;
+
+    ref<Store> getDstStore();
+};
+
 struct EvalCommand : virtual StoreCommand, MixEvalArgs
 {
     EvalCommand();

src/libcmd/installables.cc

@@ -97,7 +97,7 @@ MixFlakeOptions::MixFlakeOptions()
             lockFlags.writeLockFile = false;
             lockFlags.inputOverrides.insert_or_assign(
                 flake::parseInputPath(inputPath),
-                parseFlakeRef(flakeRef, absPath(".")));
+                parseFlakeRef(flakeRef, absPath("."), true));
         }}
     });
 
@@ -158,7 +158,10 @@ SourceExprCommand::SourceExprCommand()
 
 Strings SourceExprCommand::getDefaultFlakeAttrPaths()
 {
-    return {"defaultPackage." + settings.thisSystem.get()};
+    return {
+        "packages." + settings.thisSystem.get() + ".default",
+        "defaultPackage." + settings.thisSystem.get()
+    };
 }
 
 Strings SourceExprCommand::getDefaultFlakeAttrPathPrefixes()
@@ -198,8 +201,9 @@ void SourceExprCommand::completeInstallable(std::string_view prefix)
             prefix_ = "";
         }
 
-        Value &v1(*findAlongAttrPath(*state, prefix_, *autoArgs, root).first);
-        state->forceValue(v1);
+        auto [v, pos] = findAlongAttrPath(*state, prefix_, *autoArgs, root);
+        Value &v1(*v);
+        state->forceValue(v1, pos);
         Value v2;
         state->autoCallFunction(*autoArgs, v1, v2);
 
@@ -345,6 +349,18 @@ Installable::getCursor(EvalState & state)
     return cursors[0];
 }
 
+static StorePath getDeriver(
+    ref<Store> store,
+    const Installable & i,
+    const StorePath & drvPath)
+{
+    auto derivers = store->queryValidDerivers(drvPath);
+    if (derivers.empty())
+        throw Error("'%s' does not have a known deriver", i.what());
+    // FIXME: use all derivers?
+    return *derivers.begin();
+}
+
 struct InstallableStorePath : Installable
 {
     ref<Store> store;
@@ -353,7 +369,7 @@ struct InstallableStorePath : Installable
     InstallableStorePath(ref<Store> store, StorePath && storePath)
         : store(store), storePath(std::move(storePath)) { }
 
-    std::string what() override { return store->printStorePath(storePath); }
+    std::string what() const override { return store->printStorePath(storePath); }
 
     DerivedPaths toDerivedPaths() override
     {
@@ -374,6 +390,15 @@ struct InstallableStorePath : Installable
         }
     }
 
+    StorePathSet toDrvPaths(ref<Store> store) override
+    {
+        if (storePath.isDerivation()) {
+            return {storePath};
+        } else {
+            return {getDeriver(store, *this, storePath)};
+        }
+    }
+
     std::optional<StorePath> getStorePath() override
     {
         return storePath;
@@ -402,6 +427,14 @@ DerivedPaths InstallableValue::toDerivedPaths()
     return res;
 }
 
+StorePathSet InstallableValue::toDrvPaths(ref<Store> store)
+{
+    StorePathSet res;
+    for (auto & drv : toDerivations())
+        res.insert(drv.drvPath);
+    return res;
+}
+
 struct InstallableAttrPath : InstallableValue
 {
     SourceExprCommand & cmd;
@@ -412,12 +445,12 @@ struct InstallableAttrPath : InstallableValue
         : InstallableValue(state), cmd(cmd), v(allocRootValue(v)), attrPath(attrPath)
     { }
 
-    std::string what() override { return attrPath; }
+    std::string what() const override { return attrPath; }
 
     std::pair<Value *, Pos> toValue(EvalState & state) override
     {
         auto [vRes, pos] = findAlongAttrPath(state, attrPath, *cmd.getAutoArgs(state), **v);
-        state.forceValue(*vRes);
+        state.forceValue(*vRes, pos);
         return {vRes, pos};
     }
 
@@ -467,7 +500,7 @@ Value * InstallableFlake::getFlakeOutputs(EvalState & state, const flake::Locked
     auto aOutputs = vFlake->attrs->get(state.symbols.create("outputs"));
     assert(aOutputs);
 
-    state.forceValue(*aOutputs->value);
+    state.forceValue(*aOutputs->value, [&]() { return aOutputs->value->determinePos(noPos); });
 
     return aOutputs->value;
 }
@@ -492,7 +525,7 @@ ref<eval_cache::EvalCache> openEvalCache(
             auto vFlake = state.allocValue();
             flake::callFlake(state, *lockedFlake, *vFlake);
 
-            state.forceAttrs(*vFlake);
+            state.forceAttrs(*vFlake, noPos);
 
             auto aOutputs = vFlake->attrs->get(state.symbols.create("outputs"));
             assert(aOutputs);
@@ -515,13 +548,14 @@ InstallableFlake::InstallableFlake(
     SourceExprCommand * cmd,
     ref<EvalState> state,
     FlakeRef && flakeRef,
-    Strings && attrPaths,
-    Strings && prefixes,
+    std::string_view fragment,
+    Strings attrPaths,
+    Strings prefixes,
     const flake::LockFlags & lockFlags)
     : InstallableValue(state),
       flakeRef(flakeRef),
-      attrPaths(attrPaths),
-      prefixes(prefixes),
+      attrPaths(fragment == "" ? attrPaths : Strings{(std::string) fragment}),
+      prefixes(fragment == "" ? Strings{} : prefixes),
       lockFlags(lockFlags)
 {
     if (cmd && cmd->getAutoArgs(*state)->size())
@@ -538,6 +572,8 @@ std::tuple<std::string, FlakeRef, InstallableValue::DerivationInfo> InstallableF
     auto root = cache->getRoot();
 
     for (auto & attrPath : getActualAttrPaths()) {
+        debug("trying flake output attribute '%s'", attrPath);
+
         auto attr = root->findAlongAttrPath(
             parseAttrPath(*state, attrPath),
             true
@@ -581,7 +617,7 @@ std::pair<Value *, Pos> InstallableFlake::toValue(EvalState & state)
     for (auto & attrPath : getActualAttrPaths()) {
         try {
             auto [v, pos] = findAlongAttrPath(state, attrPath, *emptyArgs, *vOutputs);
-            state.forceValue(*v);
+            state.forceValue(*v, pos);
             return {v, pos};
         } catch (AttrPathNotFound & e) {
         }
@@ -680,7 +716,8 @@ std::vector<std::shared_ptr<Installable>> SourceExprCommand::parseInstallables(
                         this,
                         getEvalState(),
                         std::move(flakeRef),
-                        fragment == "" ? getDefaultFlakeAttrPaths() : Strings{fragment},
+                        fragment,
+                        getDefaultFlakeAttrPaths(),
                         getDefaultFlakeAttrPathPrefixes(),
                         lockFlags));
                 continue;
@@ -838,11 +875,7 @@ StorePathSet toDerivations(
                 [&](const DerivedPath::Opaque & bo) {
                     if (!useDeriver)
                         throw Error("argument '%s' did not evaluate to a derivation", i->what());
-                    auto derivers = store->queryValidDerivers(bo.path);
-                    if (derivers.empty())
-                        throw Error("'%s' does not have a known deriver", i->what());
-                    // FIXME: use all derivers?
-                    drvPaths.insert(*derivers.begin());
+                    drvPaths.insert(getDeriver(store, *i, bo.path));
                 },
                 [&](const DerivedPath::Built & bfd) {
                     drvPaths.insert(bfd.drvPath);

src/libcmd/installables.hh

@@ -33,10 +33,15 @@ struct Installable
 {
     virtual ~Installable() { }
 
-    virtual std::string what() = 0;
+    virtual std::string what() const = 0;
 
     virtual DerivedPaths toDerivedPaths() = 0;
 
+    virtual StorePathSet toDrvPaths(ref<Store> store)
+    {
+        throw Error("'%s' cannot be converted to a derivation path", what());
+    }
+
     DerivedPath toDerivedPath();
 
     UnresolvedApp toApp(EvalState & state);
@@ -81,6 +86,8 @@ struct InstallableValue : Installable
     virtual std::vector<DerivationInfo> toDerivations() = 0;
 
     DerivedPaths toDerivedPaths() override;
+
+    StorePathSet toDrvPaths(ref<Store> store) override;
 };
 
 struct InstallableFlake : InstallableValue
@@ -95,11 +102,12 @@ struct InstallableFlake : InstallableValue
         SourceExprCommand * cmd,
         ref<EvalState> state,
         FlakeRef && flakeRef,
-        Strings && attrPaths,
-        Strings && prefixes,
+        std::string_view fragment,
+        Strings attrPaths,
+        Strings prefixes,
         const flake::LockFlags & lockFlags);
 
-    std::string what() override { return flakeRef.to_string() + "#" + *attrPaths.begin(); }
+    std::string what() const override { return flakeRef.to_string() + "#" + *attrPaths.begin(); }
 
     std::vector<std::string> getActualAttrPaths();
 

src/libcmd/local.mk

@@ -8,7 +8,7 @@ libcmd_SOURCES := $(wildcard $(d)/*.cc)
 
 libcmd_CXXFLAGS += -I src/libutil -I src/libstore -I src/libexpr -I src/libmain -I src/libfetchers
 
-libcmd_LDFLAGS += -llowdown -pthread
+libcmd_LDFLAGS += $(LOWDOWN_LIBS) -pthread
 
 libcmd_LIBS = libstore libutil libexpr libmain libfetchers
 

src/libexpr/attr-path.cc

@@ -9,7 +9,7 @@ namespace nix {
 static Strings parseAttrPath(std::string_view s)
 {
     Strings res;
-    string cur;
+    std::string cur;
     auto i = s.begin();
     while (i != s.end()) {
         if (*i == '.') {
@@ -41,7 +41,7 @@ std::vector<Symbol> parseAttrPath(EvalState & state, std::string_view s)
 }
 
 
-std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const string & attrPath,
+std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const std::string & attrPath,
     Bindings & autoArgs, Value & vIn)
 {
     Strings tokens = parseAttrPath(attrPath);
@@ -58,7 +58,7 @@ std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const string & attr
         Value * vNew = state.allocValue();
         state.autoCallFunction(autoArgs, *v, *vNew);
         v = vNew;
-        state.forceValue(*v);
+        state.forceValue(*v, noPos);
 
         /* It should evaluate to either a set or an expression,
            according to what is specified in the attrPath. */
@@ -121,7 +121,7 @@ Pos findPackageFilename(EvalState & state, Value & v, std::string what)
     std::string filename(pos, 0, colon);
     unsigned int lineno;
     try {
-        lineno = std::stoi(std::string(pos, colon + 1));
+        lineno = std::stoi(std::string(pos, colon + 1, std::string::npos));
     } catch (std::invalid_argument & e) {
         throw ParseError("cannot parse line number '%s'", pos);
     }

src/libexpr/attr-path.hh

@@ -10,8 +10,11 @@ namespace nix {
 MakeError(AttrPathNotFound, Error);
 MakeError(NoPositionInfo, Error);
 
-std::pair<Value *, Pos> findAlongAttrPath(EvalState & state, const string & attrPath,
-    Bindings & autoArgs, Value & vIn);
+std::pair<Value *, Pos> findAlongAttrPath(
+    EvalState & state,
+    const std::string & attrPath,
+    Bindings & autoArgs,
+    Value & vIn);
 
 /* Heuristic to find the filename and lineno or a nix value. */
 Pos findPackageFilename(EvalState & state, Value & v, std::string what);

src/libexpr/attr-set.hh

@@ -105,7 +105,7 @@ public:
         for (size_t n = 0; n < size_; n++)
             res.emplace_back(&attrs[n]);
         std::sort(res.begin(), res.end(), [](const Attr * a, const Attr * b) {
-            return (const string &) a->name < (const string &) b->name;
+            return (const std::string &) a->name < (const std::string &) b->name;
         });
         return res;
     }
@@ -121,6 +121,8 @@ class BindingsBuilder
     Bindings * bindings;
 
 public:
+    // needed by std::back_inserter
+    using value_type = Attr;
 
     EvalState & state;
 
@@ -134,6 +136,11 @@ public:
     }
 
     void insert(const Attr & attr)
+    {
+        push_back(attr);
+    }
+
+    void push_back(const Attr & attr)
     {
         bindings->push_back(attr);
     }

src/libexpr/common-eval-args.cc

@@ -77,7 +77,7 @@ Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
     for (auto & i : autoArgs) {
         auto v = state.allocValue();
         if (i.second[0] == 'E')
-            state.mkThunk_(*v, state.parseExprFromString(string(i.second, 1), absPath(".")));
+            state.mkThunk_(*v, state.parseExprFromString(i.second.substr(1), absPath(".")));
         else
             v->mkString(((std::string_view) i.second).substr(1));
         res.insert(state.symbols.create(i.first), v);
@@ -85,17 +85,17 @@ Bindings * MixEvalArgs::getAutoArgs(EvalState & state)
     return res.finish();
 }
 
-Path lookupFileArg(EvalState & state, string s)
+Path lookupFileArg(EvalState & state, std::string_view s)
 {
     if (isUri(s)) {
         return state.store->toRealPath(
             fetchers::downloadTarball(
                 state.store, resolveUri(s), "source", false).first.storePath);
     } else if (s.size() > 2 && s.at(0) == '<' && s.at(s.size() - 1) == '>') {
-        Path p = s.substr(1, s.size() - 2);
+        Path p(s.substr(1, s.size() - 2));
         return state.findFile(p);
     } else
-        return absPath(s);
+        return absPath(std::string(s));
 }
 
 }

src/libexpr/common-eval-args.hh

@@ -22,6 +22,6 @@ private:
     std::map<std::string, std::string> autoArgs;
 };
 
-Path lookupFileArg(EvalState & state, string s);
+Path lookupFileArg(EvalState & state, std::string_view s);
 
 }

src/libexpr/eval-cache.cc

@@ -336,7 +336,7 @@ Value & AttrCursor::getValue()
     if (!_value) {
         if (parent) {
             auto & vParent = parent->first->getValue();
-            root->state.forceAttrs(vParent);
+            root->state.forceAttrs(vParent, noPos);
             auto attr = vParent.attrs->get(parent->second);
             if (!attr)
                 throw Error("attribute '%s' is unexpectedly missing", getAttrPathStr());
@@ -381,7 +381,7 @@ Value & AttrCursor::forceValue()
     auto & v = getValue();
 
     try {
-        root->state.forceValue(v);
+        root->state.forceValue(v, noPos);
     } catch (EvalError &) {
         debug("setting '%s' to failed", getAttrPathStr());
         if (root->db)
@@ -596,7 +596,7 @@ std::vector<Symbol> AttrCursor::getAttrs()
     for (auto & attr : *getValue().attrs)
         attrs.push_back(attr.name);
     std::sort(attrs.begin(), attrs.end(), [](const Symbol & a, const Symbol & b) {
-        return (const string &) a < (const string &) b;
+        return (const std::string &) a < (const std::string &) b;
     });
 
     if (root->db)

src/libexpr/eval-inline.hh

@@ -15,12 +15,6 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s))
     });
 }
 
-LocalNoInlineNoReturn(void throwTypeError(const char * s, const Value & v))
-{
-    throw TypeError(s, showType(v));
-}
-
-
 LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const Value & v))
 {
     throw TypeError({
@@ -31,6 +25,13 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
 
 
 void EvalState::forceValue(Value & v, const Pos & pos)
+{
+    forceValue(v, [&]() { return pos; });
+}
+
+
+template<typename Callable>
+void EvalState::forceValue(Value & v, Callable getPos)
 {
     if (v.isThunk()) {
         Env * env = v.thunk.env;
@@ -47,31 +48,22 @@ void EvalState::forceValue(Value & v, const Pos & pos)
     else if (v.isApp())
         callFunction(*v.app.left, *v.app.right, v, noPos);
     else if (v.isBlackhole())
-        throwEvalError(pos, "infinite recursion encountered");
-}
-
-
-inline void EvalState::forceAttrs(Value & v)
-{
-    forceValue(v);
-    if (v.type() != nAttrs)
-        throwTypeError("value is %1% while a set was expected", v);
+        throwEvalError(getPos(), "infinite recursion encountered");
 }
 
 
 inline void EvalState::forceAttrs(Value & v, const Pos & pos)
 {
-    forceValue(v, pos);
-    if (v.type() != nAttrs)
-        throwTypeError(pos, "value is %1% while a set was expected", v);
+    forceAttrs(v, [&]() { return pos; });
 }
 
 
-inline void EvalState::forceList(Value & v)
+template <typename Callable>
+inline void EvalState::forceAttrs(Value & v, Callable getPos)
 {
-    forceValue(v);
-    if (!v.isList())
-        throwTypeError("value is %1% while a list was expected", v);
+    forceValue(v, getPos);
+    if (v.type() != nAttrs)
+        throwTypeError(getPos(), "value is %1% while a set was expected", v);
 }
 
 

src/libexpr/eval.cc

@@ -1,5 +1,6 @@
 #include "eval.hh"
 #include "hash.hh"
+#include "types.hh"
 #include "util.hh"
 #include "store-api.hh"
 #include "derivations.hh"
@@ -36,6 +37,19 @@
 namespace nix {
 
 
+static char * allocString(size_t size)
+{
+    char * t;
+#if HAVE_BOEHMGC
+    t = (char *) GC_MALLOC_ATOMIC(size);
+#else
+    t = malloc(size);
+#endif
+    if (!t) throw std::bad_alloc();
+    return t;
+}
+
+
 static char * dupString(const char * s)
 {
     char * t;
@@ -169,7 +183,7 @@ const Value *getPrimOp(const Value &v) {
     return primOp;
 }
 
-string showType(ValueType type)
+std::string_view showType(ValueType type)
 {
     switch (type) {
         case nInt: return "an integer";
@@ -188,20 +202,20 @@ string showType(ValueType type)
 }
 
 
-string showType(const Value & v)
+std::string showType(const Value & v)
 {
     switch (v.internalType) {
         case tString: return v.string.context ? "a string with context" : "a string";
         case tPrimOp:
-            return fmt("the built-in function '%s'", string(v.primOp->name));
+            return fmt("the built-in function '%s'", std::string(v.primOp->name));
         case tPrimOpApp:
-            return fmt("the partially applied built-in function '%s'", string(getPrimOp(v)->primOp->name));
+            return fmt("the partially applied built-in function '%s'", std::string(getPrimOp(v)->primOp->name));
         case tExternal: return v.external->showType();
         case tThunk: return "a thunk";
         case tApp: return "a function application";
         case tBlackhole: return "a black hole";
     default:
-        return showType(v.type());
+        return std::string(showType(v.type()));
     }
 }
 
@@ -342,7 +356,7 @@ void initGC()
 
 /* Very hacky way to parse $NIX_PATH, which is colon-separated, but
    can contain URLs (e.g. "nixpkgs=https://bla...:foo=https://"). */
-static Strings parseNixPath(const string & s)
+static Strings parseNixPath(const std::string & s)
 {
     Strings res;
 
@@ -412,11 +426,21 @@ EvalState::EvalState(
     , sDescription(symbols.create("description"))
     , sSelf(symbols.create("self"))
     , sEpsilon(symbols.create(""))
+    , sStartSet(symbols.create("startSet"))
+    , sOperator(symbols.create("operator"))
+    , sKey(symbols.create("key"))
+    , sPath(symbols.create("path"))
+    , sPrefix(symbols.create("prefix"))
     , repair(NoRepair)
     , emptyBindings(0)
     , store(store)
     , buildStore(buildStore ? buildStore : store)
     , regexCache(makeRegexCache())
+#if HAVE_BOEHMGC
+    , valueAllocCache(std::allocate_shared<void *>(traceable_allocator<void *>(), nullptr))
+#else
+    , valueAllocCache(std::make_shared<void *>(nullptr))
+#endif
     , baseEnv(allocEnv(128))
     , staticBaseEnv(false, 0)
 {
@@ -582,7 +606,7 @@ Path EvalState::toRealPath(const Path & path, const PathSet & context)
 }
 
 
-Value * EvalState::addConstant(const string & name, Value & v)
+Value * EvalState::addConstant(const std::string & name, Value & v)
 {
     Value * v2 = allocValue();
     *v2 = v;
@@ -591,19 +615,19 @@ Value * EvalState::addConstant(const string & name, Value & v)
 }
 
 
-void EvalState::addConstant(const string & name, Value * v)
+void EvalState::addConstant(const std::string & name, Value * v)
 {
     staticBaseEnv.vars.emplace_back(symbols.create(name), baseEnvDispl);
     baseEnv.values[baseEnvDispl++] = v;
-    string name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
+    auto name2 = name.substr(0, 2) == "__" ? name.substr(2) : name;
     baseEnv.values[0]->attrs->push_back(Attr(symbols.create(name2), v));
 }
 
 
-Value * EvalState::addPrimOp(const string & name,
+Value * EvalState::addPrimOp(const std::string & name,
     size_t arity, PrimOpFun primOp)
 {
-    auto name2 = string(name, 0, 2) == "__" ? string(name, 2) : name;
+    auto name2 = name.substr(0, 2) == "__" ? name.substr(2) : name;
     Symbol sym = symbols.create(name2);
 
     /* Hack to make constants lazy: turn them into a application of
@@ -651,7 +675,7 @@ Value * EvalState::addPrimOp(PrimOp && primOp)
 }
 
 
-Value & EvalState::getBuiltin(const string & name)
+Value & EvalState::getBuiltin(const std::string & name)
 {
     return *baseEnv.values[0]->attrs->find(symbols.create(name))->value;
 }
@@ -679,12 +703,12 @@ std::optional<EvalState::Doc> EvalState::getDoc(Value & v)
    evaluator.  So here are some helper functions for throwing
    exceptions. */
 
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const std::string & s2))
 {
     throw EvalError(s, s2);
 }
 
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const std::string & s2))
 {
     throw EvalError({
         .msg = hintfmt(s, s2),
@@ -692,12 +716,12 @@ LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const
     });
 }
 
-LocalNoInlineNoReturn(void throwEvalError(const char * s, const string & s2, const string & s3))
+LocalNoInlineNoReturn(void throwEvalError(const char * s, const std::string & s2, const std::string & s3))
 {
     throw EvalError(s, s2, s3);
 }
 
-LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const string & s2, const string & s3))
+LocalNoInlineNoReturn(void throwEvalError(const Pos & pos, const char * s, const std::string & s2, const std::string & s3))
 {
     throw EvalError({
         .msg = hintfmt(s, s2, s3),
@@ -730,7 +754,12 @@ LocalNoInlineNoReturn(void throwTypeError(const Pos & pos, const char * s, const
     });
 }
 
-LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwTypeError(const char * s, const Value & v))
+{
+    throw TypeError(s, showType(v));
+}
+
+LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s, const std::string & s1))
 {
     throw AssertionError({
         .msg = hintfmt(s, s1),
@@ -738,7 +767,7 @@ LocalNoInlineNoReturn(void throwAssertionError(const Pos & pos, const char * s,
     });
 }
 
-LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char * s, const std::string & s1))
 {
     throw UndefinedVarError({
         .msg = hintfmt(s, s1),
@@ -746,7 +775,7 @@ LocalNoInlineNoReturn(void throwUndefinedVarError(const Pos & pos, const char *
     });
 }
 
-LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const string & s1))
+LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char * s, const std::string & s1))
 {
     throw MissingArgumentError({
         .msg = hintfmt(s, s1),
@@ -754,12 +783,12 @@ LocalNoInlineNoReturn(void throwMissingArgumentError(const Pos & pos, const char
     });
 }
 
-LocalNoInline(void addErrorTrace(Error & e, const char * s, const string & s2))
+LocalNoInline(void addErrorTrace(Error & e, const char * s, const std::string & s2))
 {
     e.addTrace(std::nullopt, s, s2);
 }
 
-LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, const string & s2))
+LocalNoInline(void addErrorTrace(Error & e, const Pos & pos, const char * s, const std::string & s2))
 {
     e.addTrace(pos, s, s2);
 }
@@ -771,17 +800,28 @@ void Value::mkString(std::string_view s)
 }
 
 
+static void copyContextToValue(Value & v, const PathSet & context)
+{
+    if (!context.empty()) {
+        size_t n = 0;
+        v.string.context = (const char * *)
+            allocBytes((context.size() + 1) * sizeof(char *));
+        for (auto & i : context)
+            v.string.context[n++] = dupString(i.c_str());
+        v.string.context[n] = 0;
+    }
+}
+
 void Value::mkString(std::string_view s, const PathSet & context)
 {
     mkString(s);
-    if (!context.empty()) {
-        size_t n = 0;
-        string.context = (const char * *)
-            allocBytes((context.size() + 1) * sizeof(char *));
-        for (auto & i : context)
-            string.context[n++] = dupString(i.c_str());
-        string.context[n] = 0;
+    copyContextToValue(*this, context);
 }
+
+void Value::mkStringMove(const char * s, const PathSet & context)
+{
+    mkString(s);
+    copyContextToValue(*this, context);
 }
 
 
@@ -823,15 +863,15 @@ Value * EvalState::allocValue()
        GC_malloc_many returns a linked list of objects of the given size, where the first word
        of each object is also the pointer to the next object in the list. This also means that we
        have to explicitly clear the first word of every object we take. */
-    if (!valueAllocCache) {
-        valueAllocCache = GC_malloc_many(sizeof(Value));
-        if (!valueAllocCache) throw std::bad_alloc();
+    if (!*valueAllocCache) {
+        *valueAllocCache = GC_malloc_many(sizeof(Value));
+        if (!*valueAllocCache) throw std::bad_alloc();
     }
 
     /* GC_NEXT is a convenience macro for accessing the first word of an object.
        Take the first list item, advance the list to the next item, and clear the next pointer. */
-    void * p = valueAllocCache;
-    GC_PTR_STORE_AND_DIRTY(&valueAllocCache, GC_NEXT(p));
+    void * p = *valueAllocCache;
+    GC_PTR_STORE_AND_DIRTY(&*valueAllocCache, GC_NEXT(p));
     GC_NEXT(p) = nullptr;
 
     nrValues++;
@@ -1103,7 +1143,7 @@ void ExprAttrs::eval(EvalState & state, Env & env, Value & v)
            Hence we need __overrides.) */
         if (hasOverrides) {
             Value * vOverrides = (*v.attrs)[overrides->second.displ].value;
-            state.forceAttrs(*vOverrides);
+            state.forceAttrs(*vOverrides, [&]() { return vOverrides->determinePos(noPos); });
             Bindings * newBnds = state.allocBindings(v.attrs->capacity() + vOverrides->attrs->size());
             for (auto & i : *v.attrs)
                 newBnds->push_back(i);
@@ -1181,7 +1221,7 @@ void ExprVar::eval(EvalState & state, Env & env, Value & v)
 }
 
 
-static string showAttrPath(EvalState & state, Env & env, const AttrPath & attrPath)
+static std::string showAttrPath(EvalState & state, Env & env, const AttrPath & attrPath)
 {
     std::ostringstream out;
     bool first = true;
@@ -1251,7 +1291,7 @@ void ExprOpHasAttr::eval(EvalState & state, Env & env, Value & v)
     e->eval(state, env, vTmp);
 
     for (auto & i : attrPath) {
-        state.forceValue(*vAttrs);
+        state.forceValue(*vAttrs, noPos);
         Bindings::iterator j;
         Symbol name = getName(i, state, env);
         if (vAttrs->type() != nAttrs ||
@@ -1339,7 +1379,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                     /* Nope, so show the first unexpected argument to the
                        user. */
                     for (auto & i : *args[0]->attrs)
-                        if (!lambda.formals->argNames.count(i.name))
+                        if (!lambda.formals->has(i.name))
                             throwTypeError(pos, "%1% called with unexpected argument '%2%'", lambda, i.name);
                     abort(); // can't happen
                 }
@@ -1355,7 +1395,7 @@ void EvalState::callFunction(Value & fun, size_t nrArgs, Value * * args, Value &
                 if (loggerSettings.showTrace.get()) {
                     addErrorTrace(e, lambda.pos, "while evaluating %s",
                         (lambda.name.set()
-                            ? "'" + (string) lambda.name + "'"
+                            ? "'" + (const std::string &) lambda.name + "'"
                             : "anonymous lambda"));
                     addErrorTrace(e, pos, "from call site%s", "");
                 }
@@ -1465,14 +1505,16 @@ void EvalState::incrFunctionCall(ExprLambda * fun)
 
 void EvalState::autoCallFunction(Bindings & args, Value & fun, Value & res)
 {
-    forceValue(fun);
+    auto pos = fun.determinePos(noPos);
+
+    forceValue(fun, pos);
 
     if (fun.type() == nAttrs) {
         auto found = fun.attrs->find(sFunctor);
         if (found != fun.attrs->end()) {
             Value * v = allocValue();
-            callFunction(*found->value, fun, *v, noPos);
-            forceValue(*v);
+            callFunction(*found->value, fun, *v, pos);
+            forceValue(*v, pos);
             return autoCallFunction(args, *v, res);
         }
     }
@@ -1660,15 +1702,39 @@ void EvalState::concatLists(Value & v, size_t nrLists, Value * * lists, const Po
 void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
 {
     PathSet context;
-    std::ostringstream s;
+    std::vector<BackedStringView> s;
+    size_t sSize = 0;
     NixInt n = 0;
     NixFloat nf = 0;
 
     bool first = !forceString;
     ValueType firstType = nString;
 
+    const auto str = [&] {
+        std::string result;
+        result.reserve(sSize);
+        for (const auto & part : s) result += *part;
+        return result;
+    };
+    /* c_str() is not str().c_str() because we want to create a string
+       Value. allocating a GC'd string directly and moving it into a
+       Value lets us avoid an allocation and copy. */
+    const auto c_str = [&] {
+        char * result = allocString(sSize + 1);
+        char * tmp = result;
+        for (const auto & part : s) {
+            memcpy(tmp, part->data(), part->size());
+            tmp += part->size();
+        }
+        *tmp = 0;
+        return result;
+    };
+
+    Value values[es->size()];
+    Value * vTmpP = values;
+
     for (auto & [i_pos, i] : *es) {
-        Value vTmp;
+        Value & vTmp = *vTmpP++;
         i->eval(state, env, vTmp);
 
         /* If the first element is a path, then the result will also
@@ -1696,11 +1762,15 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
                 nf += vTmp.fpoint;
             } else
                 throwEvalError(i_pos, "cannot add %1% to a float", showType(vTmp));
-        } else
+        } else {
+            if (s.empty()) s.reserve(es->size());
             /* skip canonization of first path, which would only be not
             canonized in the first place if it's coming from a ./${foo} type
             path */
-            s << state.coerceToString(i_pos, vTmp, context, false, firstType == nString, !first);
+            auto part = state.coerceToString(i_pos, vTmp, context, false, firstType == nString, !first);
+            sSize += part->size();
+            s.emplace_back(std::move(part));
+        }
 
         first = false;
     }
@@ -1712,9 +1782,9 @@ void ExprConcatStrings::eval(EvalState & state, Env & env, Value & v)
     else if (firstType == nPath) {
         if (!context.empty())
             throwEvalError(pos, "a string that refers to a store path cannot be appended to a path");
-        v.mkPath(canonPath(s.str()));
+        v.mkPath(canonPath(str()));
     } else
-        v.mkString(s.str(), context);
+        v.mkStringMove(c_str(), context);
 }
 
 
@@ -1733,7 +1803,7 @@ void EvalState::forceValueDeep(Value & v)
     recurse = [&](Value & v) {
         if (!seen.insert(&v).second) return;
 
-        forceValue(v);
+        forceValue(v, [&]() { return v.determinePos(noPos); });
 
         if (v.type() == nAttrs) {
             for (auto & i : *v.attrs)
@@ -1798,7 +1868,7 @@ void EvalState::forceFunction(Value & v, const Pos & pos)
 }
 
 
-string EvalState::forceString(Value & v, const Pos & pos)
+std::string_view EvalState::forceString(Value & v, const Pos & pos)
 {
     forceValue(v, pos);
     if (v.type() != nString) {
@@ -1807,13 +1877,13 @@ string EvalState::forceString(Value & v, const Pos & pos)
         else
             throwTypeError("value is %1% while a string was expected", v);
     }
-    return string(v.string.s);
+    return v.string.s;
 }
 
 
 /* Decode a context string ‘!<name>!<path>’ into a pair <path,
    name>. */
-std::pair<string, string> decodeContext(std::string_view s)
+std::pair<std::string, std::string> decodeContext(std::string_view s)
 {
     if (s.at(0) == '!') {
         size_t index = s.find("!", 1);
@@ -1842,17 +1912,17 @@ std::vector<std::pair<Path, std::string>> Value::getContext()
 }
 
 
-string EvalState::forceString(Value & v, PathSet & context, const Pos & pos)
+std::string_view EvalState::forceString(Value & v, PathSet & context, const Pos & pos)
 {
-    string s = forceString(v, pos);
+    auto s = forceString(v, pos);
     copyContext(v, context);
     return s;
 }
 
 
-string EvalState::forceStringNoCtx(Value & v, const Pos & pos)
+std::string_view EvalState::forceStringNoCtx(Value & v, const Pos & pos)
 {
-    string s = forceString(v, pos);
+    auto s = forceString(v, pos);
     if (v.string.context) {
         if (pos)
             throwEvalError(pos, "the string '%1%' is not allowed to refer to a store path (such as '%2%')",
@@ -1870,47 +1940,48 @@ bool EvalState::isDerivation(Value & v)
     if (v.type() != nAttrs) return false;
     Bindings::iterator i = v.attrs->find(sType);
     if (i == v.attrs->end()) return false;
-    forceValue(*i->value);
+    forceValue(*i->value, *i->pos);
     if (i->value->type() != nString) return false;
     return strcmp(i->value->string.s, "derivation") == 0;
 }
 
 
-std::optional<string> EvalState::tryAttrsToString(const Pos & pos, Value & v,
+std::optional<std::string> EvalState::tryAttrsToString(const Pos & pos, Value & v,
     PathSet & context, bool coerceMore, bool copyToStore)
 {
     auto i = v.attrs->find(sToString);
     if (i != v.attrs->end()) {
         Value v1;
         callFunction(*i->value, v, v1, pos);
-        return coerceToString(pos, v1, context, coerceMore, copyToStore);
+        return coerceToString(pos, v1, context, coerceMore, copyToStore).toOwned();
     }
 
     return {};
 }
 
-string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
+BackedStringView EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
     bool coerceMore, bool copyToStore, bool canonicalizePath)
 {
     forceValue(v, pos);
 
-    string s;
-
     if (v.type() == nString) {
         copyContext(v, context);
-        return v.string.s;
+        return std::string_view(v.string.s);
     }
 
     if (v.type() == nPath) {
-        Path path(canonicalizePath ? canonPath(v.path) : v.path);
-        return copyToStore ? copyPathToStore(context, path) : path;
+        BackedStringView path(PathView(v.path));
+        if (canonicalizePath)
+            path = canonPath(*path);
+        if (copyToStore)
+            path = copyPathToStore(context, std::move(path).toOwned());
+        return path;
     }
 
     if (v.type() == nAttrs) {
         auto maybeString = tryAttrsToString(pos, v, context, coerceMore, copyToStore);
-        if (maybeString) {
-            return *maybeString;
-        }
+        if (maybeString)
+            return std::move(*maybeString);
         auto i = v.attrs->find(sOutPath);
         if (i == v.attrs->end()) throwTypeError(pos, "cannot coerce a set to a string");
         return coerceToString(pos, *i->value, context, coerceMore, copyToStore);
@@ -1930,16 +2001,15 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
         if (v.type() == nNull) return "";
 
         if (v.isList()) {
-            string result;
+            std::string result;
             for (auto [n, v2] : enumerate(v.listItems())) {
-                result += coerceToString(pos, *v2,
-                    context, coerceMore, copyToStore);
+                result += *coerceToString(pos, *v2, context, coerceMore, copyToStore);
                 if (n < v.listSize() - 1
                     /* !!! not quite correct */
                     && (!v2->isList() || v2->listSize() != 0))
                     result += " ";
             }
-            return result;
+            return std::move(result);
         }
     }
 
@@ -1947,7 +2017,7 @@ string EvalState::coerceToString(const Pos & pos, Value & v, PathSet & context,
 }
 
 
-string EvalState::copyPathToStore(PathSet & context, const Path & path)
+std::string EvalState::copyPathToStore(PathSet & context, const Path & path)
 {
     if (nix::isDerivation(path))
         throwEvalError("file names are not allowed to end in '%1%'", drvExtension);
@@ -1973,7 +2043,7 @@ string EvalState::copyPathToStore(PathSet & context, const Path & path)
 
 Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
 {
-    string path = coerceToString(pos, v, context, false, false);
+    auto path = coerceToString(pos, v, context, false, false).toOwned();
     if (path == "" || path[0] != '/')
         throwEvalError(pos, "string '%1%' doesn't represent an absolute path", path);
     return path;
@@ -1982,8 +2052,8 @@ Path EvalState::coerceToPath(const Pos & pos, Value & v, PathSet & context)
 
 bool EvalState::eqValues(Value & v1, Value & v2)
 {
-    forceValue(v1);
-    forceValue(v2);
+    forceValue(v1, noPos);
+    forceValue(v2, noPos);
 
     /* !!! Hack to support some old broken code that relies on pointer
        equality tests between sets.  (Specifically, builderDefs calls
@@ -2143,11 +2213,11 @@ void EvalState::printStats()
                 for (auto & i : functionCalls) {
                     auto obj = list.object();
                     if (i.first->name.set())
-                        obj.attr("name", (const string &) i.first->name);
+                        obj.attr("name", (const std::string &) i.first->name);
                     else
                         obj.attr("name", nullptr);
                     if (i.first->pos) {
-                        obj.attr("file", (const string &) i.first->pos.file);
+                        obj.attr("file", (const std::string &) i.first->pos.file);
                         obj.attr("line", i.first->pos.line);
                         obj.attr("column", i.first->pos.column);
                     }
@@ -2159,7 +2229,7 @@ void EvalState::printStats()
                 for (auto & i : attrSelects) {
                     auto obj = list.object();
                     if (i.first) {
-                        obj.attr("file", (const string &) i.first.file);
+                        obj.attr("file", (const std::string &) i.first.file);
                         obj.attr("line", i.first.line);
                         obj.attr("column", i.first.column);
                     }
@@ -2176,7 +2246,7 @@ void EvalState::printStats()
 }
 
 
-string ExternalValueBase::coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const
+std::string ExternalValueBase::coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const
 {
     throw TypeError({
         .msg = hintfmt("cannot coerce %1% to a string", showType()),

src/libexpr/eval.hh

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "attr-set.hh"
+#include "types.hh"
 #include "value.hh"
 #include "nixexpr.hh"
 #include "symbol-table.hh"
@@ -80,7 +81,8 @@ public:
         sContentAddressed,
         sOutputHash, sOutputHashAlgo, sOutputHashMode,
         sRecurseForDerivations,
-        sDescription, sSelf, sEpsilon;
+        sDescription, sSelf, sEpsilon, sStartSet, sOperator, sKey, sPath,
+        sPrefix;
     Symbol sDerivationNix;
 
     /* If set, force copying files to the Nix store even if they
@@ -132,7 +134,7 @@ private:
     std::shared_ptr<RegexCache> regexCache;
 
     /* Allocation cache for GC'd Value objects. */
-    void * valueAllocCache = nullptr;
+    std::shared_ptr<void *> valueAllocCache;
 
 public:
 
@@ -148,7 +150,7 @@ public:
         const Pos & pos
     );
 
-    void addToSearchPath(const string & s);
+    void addToSearchPath(const std::string & s);
 
     SearchPath getSearchPath() { return searchPath; }
 
@@ -179,8 +181,8 @@ public:
     Expr * parseExprFromFile(const Path & path, StaticEnv & staticEnv);
 
     /* Parse a Nix expression from the specified string. */
-    Expr * parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv);
-    Expr * parseExprFromString(std::string_view s, const Path & basePath);
+    Expr * parseExprFromString(std::string s, const Path & basePath, StaticEnv & staticEnv);
+    Expr * parseExprFromString(std::string s, const Path & basePath);
 
     Expr * parseStdin();
 
@@ -200,8 +202,8 @@ public:
     void resetFileCache();
 
     /* Look up a file in the search path. */
-    Path findFile(const string & path);
-    Path findFile(SearchPath & searchPath, const string & path, const Pos & pos = noPos);
+    Path findFile(const std::string_view path);
+    Path findFile(SearchPath & searchPath, const std::string_view path, const Pos & pos = noPos);
 
     /* If the specified search path element is a URI, download it. */
     std::pair<bool, std::string> resolveSearchPathElem(const SearchPathElem & elem);
@@ -220,7 +222,10 @@ public:
        of the evaluation of the thunk.  If `v' is a delayed function
        application, call the function and overwrite `v' with the
        result.  Otherwise, this is a no-op. */
-    inline void forceValue(Value & v, const Pos & pos = noPos);
+    inline void forceValue(Value & v, const Pos & pos);
+
+    template <typename Callable>
+    inline void forceValue(Value & v, Callable getPos);
 
     /* Force a value, then recursively force list elements and
        attributes. */
@@ -230,31 +235,34 @@ public:
     NixInt forceInt(Value & v, const Pos & pos);
     NixFloat forceFloat(Value & v, const Pos & pos);
     bool forceBool(Value & v, const Pos & pos);
-    inline void forceAttrs(Value & v);
-    inline void forceAttrs(Value & v, const Pos & pos);
-    inline void forceList(Value & v);
+
+    void forceAttrs(Value & v, const Pos & pos);
+
+    template <typename Callable>
+    inline void forceAttrs(Value & v, Callable getPos);
+
     inline void forceList(Value & v, const Pos & pos);
     void forceFunction(Value & v, const Pos & pos); // either lambda or primop
-    string forceString(Value & v, const Pos & pos = noPos);
-    string forceString(Value & v, PathSet & context, const Pos & pos = noPos);
-    string forceStringNoCtx(Value & v, const Pos & pos = noPos);
+    std::string_view forceString(Value & v, const Pos & pos = noPos);
+    std::string_view forceString(Value & v, PathSet & context, const Pos & pos = noPos);
+    std::string_view forceStringNoCtx(Value & v, const Pos & pos = noPos);
 
     /* Return true iff the value `v' denotes a derivation (i.e. a
        set with attribute `type = "derivation"'). */
     bool isDerivation(Value & v);
 
-    std::optional<string> tryAttrsToString(const Pos & pos, Value & v,
+    std::optional<std::string> tryAttrsToString(const Pos & pos, Value & v,
         PathSet & context, bool coerceMore = false, bool copyToStore = true);
 
     /* String coercion.  Converts strings, paths and derivations to a
        string.  If `coerceMore' is set, also converts nulls, integers,
        booleans and lists to a string.  If `copyToStore' is set,
        referenced paths are copied to the Nix store as a side effect. */
-    string coerceToString(const Pos & pos, Value & v, PathSet & context,
+    BackedStringView coerceToString(const Pos & pos, Value & v, PathSet & context,
         bool coerceMore = false, bool copyToStore = true,
         bool canonicalizePath = true);
 
-    string copyPathToStore(PathSet & context, const Path & path);
+    std::string copyPathToStore(PathSet & context, const Path & path);
 
     /* Path coercion.  Converts strings, paths and derivations to a
        path.  The result is guaranteed to be a canonicalised, absolute
@@ -276,18 +284,18 @@ private:
 
     void createBaseEnv();
 
-    Value * addConstant(const string & name, Value & v);
+    Value * addConstant(const std::string & name, Value & v);
 
-    void addConstant(const string & name, Value * v);
+    void addConstant(const std::string & name, Value * v);
 
-    Value * addPrimOp(const string & name,
+    Value * addPrimOp(const std::string & name,
         size_t arity, PrimOpFun primOp);
 
     Value * addPrimOp(PrimOp && primOp);
 
 public:
 
-    Value & getBuiltin(const string & name);
+    Value & getBuiltin(const std::string & name);
 
     struct Doc
     {
@@ -308,8 +316,8 @@ private:
     friend struct ExprAttrs;
     friend struct ExprLet;
 
-    Expr * parse(const char * text, FileOrigin origin, const Path & path,
-        const Path & basePath, StaticEnv & staticEnv);
+    Expr * parse(char * text, size_t length, FileOrigin origin, const PathView path,
+        const PathView basePath, StaticEnv & staticEnv);
 
 public:
 
@@ -399,18 +407,19 @@ private:
     friend struct ExprSelect;
     friend void prim_getAttr(EvalState & state, const Pos & pos, Value * * args, Value & v);
     friend void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v);
+    friend void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v);
 
     friend struct Value;
 };
 
 
 /* Return a string representing the type of the value `v'. */
-string showType(ValueType type);
-string showType(const Value & v);
+std::string_view showType(ValueType type);
+std::string showType(const Value & v);
 
 /* Decode a context string ‘!<name>!<path>’ into a pair <path,
    name>. */
-std::pair<string, string> decodeContext(std::string_view s);
+std::pair<std::string, std::string> decodeContext(std::string_view s);
 
 /* If `path' refers to a directory, then append "/default.nix". */
 Path resolveExprPath(Path path);

src/libexpr/flake/flake.cc

@@ -89,11 +89,11 @@ static void expectType(EvalState & state, ValueType type,
 
 static std::map<FlakeId, FlakeInput> parseFlakeInputs(
     EvalState & state, Value * value, const Pos & pos,
-    const std::optional<Path> & baseDir);
+    const std::optional<Path> & baseDir, InputPath lockRootPath);
 
 static FlakeInput parseFlakeInput(EvalState & state,
     const std::string & inputName, Value * value, const Pos & pos,
-    const std::optional<Path> & baseDir)
+    const std::optional<Path> & baseDir, InputPath lockRootPath)
 {
     expectType(state, nAttrs, *value, pos);
 
@@ -117,10 +117,12 @@ static FlakeInput parseFlakeInput(EvalState & state,
                 expectType(state, nBool, *attr.value, *attr.pos);
                 input.isFlake = attr.value->boolean;
             } else if (attr.name == sInputs) {
-                input.overrides = parseFlakeInputs(state, attr.value, *attr.pos, baseDir);
+                input.overrides = parseFlakeInputs(state, attr.value, *attr.pos, baseDir, lockRootPath);
             } else if (attr.name == sFollows) {
                 expectType(state, nString, *attr.value, *attr.pos);
-                input.follows = parseInputPath(attr.value->string.s);
+                auto follows(parseInputPath(attr.value->string.s));
+                follows.insert(follows.begin(), lockRootPath.begin(), lockRootPath.end());
+                input.follows = follows;
             } else {
                 switch (attr.value->type()) {
                     case nString:
@@ -166,7 +168,7 @@ static FlakeInput parseFlakeInput(EvalState & state,
 
 static std::map<FlakeId, FlakeInput> parseFlakeInputs(
     EvalState & state, Value * value, const Pos & pos,
-    const std::optional<Path> & baseDir)
+    const std::optional<Path> & baseDir, InputPath lockRootPath)
 {
     std::map<FlakeId, FlakeInput> inputs;
 
@@ -178,7 +180,8 @@ static std::map<FlakeId, FlakeInput> parseFlakeInputs(
                 inputAttr.name,
                 inputAttr.value,
                 *inputAttr.pos,
-                baseDir));
+                baseDir,
+                lockRootPath));
     }
 
     return inputs;
@@ -188,7 +191,8 @@ static Flake getFlake(
     EvalState & state,
     const FlakeRef & originalRef,
     bool allowLookup,
-    FlakeCache & flakeCache)
+    FlakeCache & flakeCache,
+    InputPath lockRootPath)
 {
     auto [sourceInfo, resolvedRef, lockedRef] = fetchOrSubstituteTree(
         state, originalRef, allowLookup, flakeCache);
@@ -223,7 +227,7 @@ static Flake getFlake(
     auto sInputs = state.symbols.create("inputs");
 
     if (auto inputs = vInfo.attrs->get(sInputs))
-        flake.inputs = parseFlakeInputs(state, inputs->value, *inputs->pos, flakeDir);
+        flake.inputs = parseFlakeInputs(state, inputs->value, *inputs->pos, flakeDir, lockRootPath);
 
     auto sOutputs = state.symbols.create("outputs");
 
@@ -250,10 +254,12 @@ static Flake getFlake(
         for (auto & setting : *nixConfig->value->attrs) {
             forceTrivialValue(state, *setting.value, *setting.pos);
             if (setting.value->type() == nString)
-                flake.config.settings.insert({setting.name, state.forceStringNoCtx(*setting.value, *setting.pos)});
+                flake.config.settings.insert({setting.name, std::string(state.forceStringNoCtx(*setting.value, *setting.pos))});
             else if (setting.value->type() == nPath) {
                 PathSet emptyContext = {};
-                flake.config.settings.insert({setting.name, state.coerceToString(*setting.pos, *setting.value, emptyContext, false, true, true)});
+                flake.config.settings.emplace(
+                    setting.name,
+                    state.coerceToString(*setting.pos, *setting.value, emptyContext, false, true, true) .toOwned());
             }
             else if (setting.value->type() == nInt)
                 flake.config.settings.insert({setting.name, state.forceInt(*setting.value, *setting.pos)});
@@ -265,7 +271,7 @@ static Flake getFlake(
                     if (elem->type() != nString)
                         throw TypeError("list element in flake configuration setting '%s' is %s while a string is expected",
                             setting.name, showType(*setting.value));
-                    ss.push_back(state.forceStringNoCtx(*elem, *setting.pos));
+                    ss.emplace_back(state.forceStringNoCtx(*elem, *setting.pos));
                 }
                 flake.config.settings.insert({setting.name, ss});
             }
@@ -287,6 +293,11 @@ static Flake getFlake(
     return flake;
 }
 
+Flake getFlake(EvalState & state, const FlakeRef & originalRef, bool allowLookup, FlakeCache & flakeCache)
+{
+    return getFlake(state, originalRef, allowLookup, flakeCache, {});
+}
+
 Flake getFlake(EvalState & state, const FlakeRef & originalRef, bool allowLookup)
 {
     FlakeCache flakeCache;
@@ -334,22 +345,12 @@ LockedFlake lockFlake(
 
         std::vector<FlakeRef> parents;
 
-        struct LockParent {
-            /* The path to this parent. */
-            InputPath path;
-
-            /* Whether we are currently inside a top-level lockfile
-               (inputs absolute) or subordinate lockfile (inputs
-               relative). */
-            bool absolute;
-        };
-
         std::function<void(
             const FlakeInputs & flakeInputs,
             std::shared_ptr<Node> node,
             const InputPath & inputPathPrefix,
             std::shared_ptr<const Node> oldNode,
-            const LockParent & parent,
+            const InputPath & lockRootPath,
             const Path & parentPath,
             bool trustLock)>
             computeLocks;
@@ -359,7 +360,7 @@ LockedFlake lockFlake(
             std::shared_ptr<Node> node,
             const InputPath & inputPathPrefix,
             std::shared_ptr<const Node> oldNode,
-            const LockParent & parent,
+            const InputPath & lockRootPath,
             const Path & parentPath,
             bool trustLock)
         {
@@ -404,17 +405,7 @@ LockedFlake lockFlake(
                     if (input.follows) {
                         InputPath target;
 
-                        if (parent.absolute && !hasOverride) {
-                            target = *input.follows;
-                        } else {
-                            if (hasOverride) {
-                                target = inputPathPrefix;
-                                target.pop_back();
-                            } else
-                                target = parent.path;
-
-                            for (auto & i : *input.follows) target.push_back(i);
-                        }
+                        target.insert(target.end(), input.follows->begin(), input.follows->end());
 
                         debug("input '%s' follows '%s'", inputPathS, printInputPath(target));
                         node->inputs.insert_or_assign(id, target);
@@ -487,30 +478,32 @@ LockedFlake lockFlake(
                                             break;
                                         }
                                     }
+                                    auto absoluteFollows(lockRootPath);
+                                    absoluteFollows.insert(absoluteFollows.end(), follows->begin(), follows->end());
                                     fakeInputs.emplace(i.first, FlakeInput {
-                                        .follows = *follows,
+                                        .follows = absoluteFollows,
                                     });
                                 }
                             }
                         }
 
-                        LockParent newParent {
-                            .path = inputPath,
-                            .absolute = true
-                        };
-
+                        auto localPath(parentPath);
+                        // If this input is a path, recurse it down.
+                        // This allows us to resolve path inputs relative to the current flake.
+                        if ((*input.ref).input.getType() == "path")
+                            localPath = absPath(*input.ref->input.getSourcePath(), parentPath);
                         computeLocks(
                             mustRefetch
-                            ? getFlake(state, oldLock->lockedRef, false, flakeCache).inputs
+                            ? getFlake(state, oldLock->lockedRef, false, flakeCache, inputPath).inputs
                             : fakeInputs,
-                            childNode, inputPath, oldLock, newParent, parentPath, !mustRefetch);
+                            childNode, inputPath, oldLock, lockRootPath, parentPath, !mustRefetch);
 
                     } else {
                         /* We need to create a new lock file entry. So fetch
                            this input. */
                         debug("creating new input '%s'", inputPathS);
 
-                        if (!lockFlags.allowMutable && !input.ref->input.isImmutable())
+                        if (!lockFlags.allowMutable && !input.ref->input.isLocked())
                             throw Error("cannot update flake input '%s' in pure mode", inputPathS);
 
                         if (input.isFlake) {
@@ -522,7 +515,7 @@ LockedFlake lockFlake(
                             if (localRef.input.getType() == "path")
                                 localPath = absPath(*input.ref->input.getSourcePath(), parentPath);
 
-                            auto inputFlake = getFlake(state, localRef, useRegistries, flakeCache);
+                            auto inputFlake = getFlake(state, localRef, useRegistries, flakeCache, inputPath);
 
                             /* Note: in case of an --override-input, we use
                                the *original* ref (input2.ref) for the
@@ -543,13 +536,6 @@ LockedFlake lockFlake(
                             parents.push_back(*input.ref);
                             Finally cleanup([&]() { parents.pop_back(); });
 
-                            // Follows paths from existing inputs in the top-level lockfile are absolute,
-                            // whereas paths in subordinate lockfiles are relative to those lockfiles.
-                            LockParent newParent {
-                                .path = inputPath,
-                                .absolute = oldLock ? true : false
-                            };
-
                             /* Recursively process the inputs of this
                                flake. Also, unless we already have this flake
                                in the top-level lock file, use this flake's
@@ -560,7 +546,7 @@ LockedFlake lockFlake(
                                 ? std::dynamic_pointer_cast<const Node>(oldLock)
                                 : LockFile::read(
                                     inputFlake.sourceInfo->actualPath + "/" + inputFlake.lockedRef.subdir + "/flake.lock").root,
-                                newParent, localPath, false);
+                                oldLock ? lockRootPath : inputPath, localPath, false);
                         }
 
                         else {
@@ -578,17 +564,12 @@ LockedFlake lockFlake(
             }
         };
 
-        LockParent parent {
-            .path = {},
-            .absolute = true
-        };
-
         // Bring in the current ref for relative path resolution if we have it
         auto parentPath = canonPath(flake.sourceInfo->actualPath + "/" + flake.lockedRef.subdir, true);
 
         computeLocks(
             flake.inputs, newLockFile.root, {},
-            lockFlags.recreateLockFile ? nullptr : oldLockFile.root, parent, parentPath, false);
+            lockFlags.recreateLockFile ? nullptr : oldLockFile.root, {}, parentPath, false);
 
         for (auto & i : lockFlags.inputOverrides)
             if (!overridesUsed.count(i.first))
@@ -635,12 +616,24 @@ LockedFlake lockFlake(
 
                         newLockFile.write(path);
 
+                        std::optional<std::string> commitMessage = std::nullopt;
+                        if (lockFlags.commitLockFile) {
+                            std::string cm;
+
+                            cm = settings.commitLockFileSummary.get();
+
+                            if (cm == "") {
+                                cm = fmt("%s: %s", relPath, lockFileExists ? "Update" : "Add");
+                            }
+
+                            cm += "\n\nFlake lock file updates:\n\n";
+                            cm += filterANSIEscapes(diff, true);
+                            commitMessage = cm;
+                        }
+
                         topRef.input.markChangedFile(
                             (topRef.subdir == "" ? "" : topRef.subdir + "/") + "flake.lock",
-                            lockFlags.commitLockFile
-                            ? std::optional<std::string>(fmt("%s: %s\n\nFlake lock file changes:\n\n%s",
-                                    relPath, lockFileExists ? "Update" : "Add", filterANSIEscapes(diff, true)))
-                            : std::nullopt);
+                            commitMessage);
 
                         /* Rewriting the lockfile changed the top-level
                            repo, so we should re-read it. FIXME: we could
@@ -659,7 +652,7 @@ LockedFlake lockFlake(
                            now. Corner case: we could have reverted from a
                            dirty to a clean tree! */
                         if (flake.lockedRef.input == prevLockedRef.input
-                            && !flake.lockedRef.input.isImmutable())
+                            && !flake.lockedRef.input.isLocked())
                             throw Error("'%s' did not change after I updated its 'flake.lock' file; is 'flake.lock' under version control?", flake.originalRef);
                     }
                 } else
@@ -716,10 +709,10 @@ static void prim_getFlake(EvalState & state, const Pos & pos, Value * * args, Va
 {
     state.requireExperimentalFeatureOnEvaluation(Xp::Flakes, "builtins.getFlake", pos);
 
-    auto flakeRefS = state.forceStringNoCtx(*args[0], pos);
+    std::string flakeRefS(state.forceStringNoCtx(*args[0], pos));
     auto flakeRef = parseFlakeRef(flakeRefS, {}, true);
-    if (evalSettings.pureEval && !flakeRef.input.isImmutable())
-        throw Error("cannot call 'getFlake' on mutable flake reference '%s', at %s (use --impure to override)", flakeRefS, pos);
+    if (evalSettings.pureEval && !flakeRef.input.isLocked())
+        throw Error("cannot call 'getFlake' on unlocked flake reference '%s', at %s (use --impure to override)", flakeRefS, pos);
 
     callFlake(state,
         lockFlake(state, flakeRef,

src/libexpr/flake/flakeref.cc

@@ -122,6 +122,28 @@ std::pair<FlakeRef, std::string> parseFlakeRefWithFragment(
 
             if (isFlake) {
 
+                if (!allowMissing && !pathExists(path + "/flake.nix")){
+                    notice("path '%s' does not contain a 'flake.nix', searching up",path);
+
+                    // Save device to detect filesystem boundary
+                    dev_t device = lstat(path).st_dev;
+                    bool found = false;
+                    while (path != "/") {
+                        if (pathExists(path + "/flake.nix")) {
+                            found = true;
+                            break;
+                        } else if (pathExists(path + "/.git"))
+                            throw Error("path '%s' is not part of a flake (neither it nor its parent directories contain a 'flake.nix' file)", path);
+                        else {
+                            if (lstat(path).st_dev != device)
+                                throw Error("unable to find a flake before encountering filesystem boundary at '%s'", path);
+                        }
+                        path = dirOf(path);
+                    }
+                    if (!found)
+                        throw BadURL("could not find a flake.nix file");
+                }
+
                 if (!S_ISDIR(lstat(path).st_mode))
                     throw BadURL("path '%s' is not a flake (because it's not a directory)", path);
 

src/libexpr/flake/lockfile.cc

@@ -35,7 +35,7 @@ LockedNode::LockedNode(const nlohmann::json & json)
     , originalRef(getFlakeRef(json, "original", nullptr))
     , isFlake(json.find("flake") != json.end() ? (bool) json["flake"] : true)
 {
-    if (!lockedRef.input.isImmutable())
+    if (!lockedRef.input.isLocked())
         throw Error("lockfile contains mutable lock '%s'",
             fetchers::attrsToJSON(lockedRef.input.toAttrs()));
 }
@@ -220,7 +220,7 @@ bool LockFile::isImmutable() const
     for (auto & i : nodes) {
         if (i == root) continue;
         auto lockedNode = std::dynamic_pointer_cast<const LockedNode>(i);
-        if (lockedNode && !lockedNode->lockedRef.input.isImmutable()) return false;
+        if (lockedNode && !lockedNode->lockedRef.input.isLocked()) return false;
     }
 
     return true;

src/libexpr/get-drvs.cc

@@ -11,8 +11,8 @@
 namespace nix {
 
 
-DrvInfo::DrvInfo(EvalState & state, const string & attrPath, Bindings * attrs)
-    : state(&state), attrs(attrs), attrPath(attrPath)
+DrvInfo::DrvInfo(EvalState & state, std::string attrPath, Bindings * attrs)
+    : state(&state), attrs(attrs), attrPath(std::move(attrPath))
 {
 }
 
@@ -47,7 +47,7 @@ DrvInfo::DrvInfo(EvalState & state, ref<Store> store, const std::string & drvPat
 }
 
 
-string DrvInfo::queryName() const
+std::string DrvInfo::queryName() const
 {
     if (name == "" && attrs) {
         auto i = attrs->find(state->sName);
@@ -58,7 +58,7 @@ string DrvInfo::queryName() const
 }
 
 
-string DrvInfo::querySystem() const
+std::string DrvInfo::querySystem() const
 {
     if (system == "" && attrs) {
         auto i = attrs->find(state->sSystem);
@@ -68,7 +68,7 @@ string DrvInfo::querySystem() const
 }
 
 
-string DrvInfo::queryDrvPath() const
+std::string DrvInfo::queryDrvPath() const
 {
     if (drvPath == "" && attrs) {
         Bindings::iterator i = attrs->find(state->sDrvPath);
@@ -79,7 +79,7 @@ string DrvInfo::queryDrvPath() const
 }
 
 
-string DrvInfo::queryOutPath() const
+std::string DrvInfo::queryOutPath() const
 {
     if (!outPath && attrs) {
         Bindings::iterator i = attrs->find(state->sOutPath);
@@ -104,10 +104,10 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool onlyOutputsToInstall)
             /* For each output... */
             for (auto elem : i->value->listItems()) {
                 /* Evaluate the corresponding set. */
-                string name = state->forceStringNoCtx(*elem, *i->pos);
+                std::string name(state->forceStringNoCtx(*elem, *i->pos));
                 Bindings::iterator out = attrs->find(state->symbols.create(name));
                 if (out == attrs->end()) continue; // FIXME: throw error?
-                state->forceAttrs(*out->value);
+                state->forceAttrs(*out->value, *i->pos);
 
                 /* And evaluate its ‘outPath’ attribute. */
                 Bindings::iterator outPath = out->value->attrs->find(state->sOutPath);
@@ -138,7 +138,7 @@ DrvInfo::Outputs DrvInfo::queryOutputs(bool onlyOutputsToInstall)
 }
 
 
-string DrvInfo::queryOutputName() const
+std::string DrvInfo::queryOutputName() const
 {
     if (outputName == "" && attrs) {
         Bindings::iterator i = attrs->find(state->sOutputName);
@@ -172,7 +172,7 @@ StringSet DrvInfo::queryMetaNames()
 
 bool DrvInfo::checkMeta(Value & v)
 {
-    state->forceValue(v);
+    state->forceValue(v, [&]() { return v.determinePos(noPos); });
     if (v.type() == nList) {
         for (auto elem : v.listItems())
             if (!checkMeta(*elem)) return false;
@@ -190,7 +190,7 @@ bool DrvInfo::checkMeta(Value & v)
 }
 
 
-Value * DrvInfo::queryMeta(const string & name)
+Value * DrvInfo::queryMeta(const std::string & name)
 {
     if (!getMeta()) return 0;
     Bindings::iterator a = meta->find(state->symbols.create(name));
@@ -199,7 +199,7 @@ Value * DrvInfo::queryMeta(const string & name)
 }
 
 
-string DrvInfo::queryMetaString(const string & name)
+std::string DrvInfo::queryMetaString(const std::string & name)
 {
     Value * v = queryMeta(name);
     if (!v || v->type() != nString) return "";
@@ -207,7 +207,7 @@ string DrvInfo::queryMetaString(const string & name)
 }
 
 
-NixInt DrvInfo::queryMetaInt(const string & name, NixInt def)
+NixInt DrvInfo::queryMetaInt(const std::string & name, NixInt def)
 {
     Value * v = queryMeta(name);
     if (!v) return def;
@@ -221,7 +221,7 @@ NixInt DrvInfo::queryMetaInt(const string & name, NixInt def)
     return def;
 }
 
-NixFloat DrvInfo::queryMetaFloat(const string & name, NixFloat def)
+NixFloat DrvInfo::queryMetaFloat(const std::string & name, NixFloat def)
 {
     Value * v = queryMeta(name);
     if (!v) return def;
@@ -236,7 +236,7 @@ NixFloat DrvInfo::queryMetaFloat(const string & name, NixFloat def)
 }
 
 
-bool DrvInfo::queryMetaBool(const string & name, bool def)
+bool DrvInfo::queryMetaBool(const std::string & name, bool def)
 {
     Value * v = queryMeta(name);
     if (!v) return def;
@@ -251,7 +251,7 @@ bool DrvInfo::queryMetaBool(const string & name, bool def)
 }
 
 
-void DrvInfo::setMeta(const string & name, Value * v)
+void DrvInfo::setMeta(const std::string & name, Value * v)
 {
     getMeta();
     auto attrs = state->buildBindings(1 + (meta ? meta->size() : 0));
@@ -266,7 +266,7 @@ void DrvInfo::setMeta(const string & name, Value * v)
 
 
 /* Cache for already considered attrsets. */
-typedef set<Bindings *> Done;
+typedef std::set<Bindings *> Done;
 
 
 /* Evaluate value `v'.  If it evaluates to a set of type `derivation',
@@ -274,11 +274,11 @@ typedef set<Bindings *> Done;
    The result boolean indicates whether it makes sense
    for the caller to recursively search for derivations in `v'. */
 static bool getDerivation(EvalState & state, Value & v,
-    const string & attrPath, DrvInfos & drvs, Done & done,
+    const std::string & attrPath, DrvInfos & drvs, Done & done,
     bool ignoreAssertionFailures)
 {
     try {
-        state.forceValue(v);
+        state.forceValue(v, [&]() { return v.determinePos(noPos); });
         if (!state.isDerivation(v)) return true;
 
         /* Remove spurious duplicates (e.g., a set like `rec { x =
@@ -311,7 +311,7 @@ std::optional<DrvInfo> getDerivation(EvalState & state, Value & v,
 }
 
 
-static string addToPath(const string & s1, const string & s2)
+static std::string addToPath(const std::string & s1, const std::string & s2)
 {
     return s1.empty() ? s2 : s1 + "." + s2;
 }
@@ -321,7 +321,7 @@ static std::regex attrRegex("[A-Za-z_][A-Za-z0-9-_+]*");
 
 
 static void getDerivations(EvalState & state, Value & vIn,
-    const string & pathPrefix, Bindings & autoArgs,
+    const std::string & pathPrefix, Bindings & autoArgs,
     DrvInfos & drvs, Done & done,
     bool ignoreAssertionFailures)
 {
@@ -346,7 +346,7 @@ static void getDerivations(EvalState & state, Value & vIn,
             debug("evaluating attribute '%1%'", i->name);
             if (!std::regex_match(std::string(i->name), attrRegex))
                 continue;
-            string pathPrefix2 = addToPath(pathPrefix, i->name);
+            std::string pathPrefix2 = addToPath(pathPrefix, i->name);
             if (combineChannels)
                 getDerivations(state, *i->value, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
             else if (getDerivation(state, *i->value, pathPrefix2, drvs, done, ignoreAssertionFailures)) {
@@ -364,7 +364,7 @@ static void getDerivations(EvalState & state, Value & vIn,
 
     else if (v.type() == nList) {
         for (auto [n, elem] : enumerate(v.listItems())) {
-            string pathPrefix2 = addToPath(pathPrefix, fmt("%d", n));
+            std::string pathPrefix2 = addToPath(pathPrefix, fmt("%d", n));
             if (getDerivation(state, *elem, pathPrefix2, drvs, done, ignoreAssertionFailures))
                 getDerivations(state, *elem, pathPrefix2, autoArgs, drvs, done, ignoreAssertionFailures);
         }
@@ -374,7 +374,7 @@ static void getDerivations(EvalState & state, Value & vIn,
 }
 
 
-void getDerivations(EvalState & state, Value & v, const string & pathPrefix,
+void getDerivations(EvalState & state, Value & v, const std::string & pathPrefix,
     Bindings & autoArgs, DrvInfos & drvs, bool ignoreAssertionFailures)
 {
     Done done;

src/libexpr/get-drvs.hh

@@ -12,16 +12,16 @@ namespace nix {
 struct DrvInfo
 {
 public:
-    typedef std::map<string, Path> Outputs;
+    typedef std::map<std::string, Path> Outputs;
 
 private:
     EvalState * state;
 
-    mutable string name;
-    mutable string system;
-    mutable string drvPath;
-    mutable std::optional<string> outPath;
-    mutable string outputName;
+    mutable std::string name;
+    mutable std::string system;
+    mutable std::string drvPath;
+    mutable std::optional<std::string> outPath;
+    mutable std::string outputName;
     Outputs outputs;
 
     bool failed = false; // set if we get an AssertionError
@@ -33,36 +33,36 @@ private:
     bool checkMeta(Value & v);
 
 public:
-    string attrPath; /* path towards the derivation */
+    std::string attrPath; /* path towards the derivation */
 
     DrvInfo(EvalState & state) : state(&state) { };
-    DrvInfo(EvalState & state, const string & attrPath, Bindings * attrs);
+    DrvInfo(EvalState & state, std::string attrPath, Bindings * attrs);
     DrvInfo(EvalState & state, ref<Store> store, const std::string & drvPathWithOutputs);
 
-    string queryName() const;
-    string querySystem() const;
-    string queryDrvPath() const;
-    string queryOutPath() const;
-    string queryOutputName() const;
+    std::string queryName() const;
+    std::string querySystem() const;
+    std::string queryDrvPath() const;
+    std::string queryOutPath() const;
+    std::string queryOutputName() const;
     /** Return the list of outputs. The "outputs to install" are determined by `meta.outputsToInstall`. */
     Outputs queryOutputs(bool onlyOutputsToInstall = false);
 
     StringSet queryMetaNames();
-    Value * queryMeta(const string & name);
-    string queryMetaString(const string & name);
-    NixInt queryMetaInt(const string & name, NixInt def);
-    NixFloat queryMetaFloat(const string & name, NixFloat def);
-    bool queryMetaBool(const string & name, bool def);
-    void setMeta(const string & name, Value * v);
+    Value * queryMeta(const std::string & name);
+    std::string queryMetaString(const std::string & name);
+    NixInt queryMetaInt(const std::string & name, NixInt def);
+    NixFloat queryMetaFloat(const std::string & name, NixFloat def);
+    bool queryMetaBool(const std::string & name, bool def);
+    void setMeta(const std::string & name, Value * v);
 
     /*
     MetaInfo queryMetaInfo(EvalState & state) const;
     MetaValue queryMetaInfo(EvalState & state, const string & name) const;
     */
 
-    void setName(const string & s) { name = s; }
-    void setDrvPath(const string & s) { drvPath = s; }
-    void setOutPath(const string & s) { outPath = s; }
+    void setName(const std::string & s) { name = s; }
+    void setDrvPath(const std::string & s) { drvPath = s; }
+    void setOutPath(const std::string & s) { outPath = s; }
 
     void setFailed() { failed = true; };
     bool hasFailed() { return failed; };
@@ -70,9 +70,9 @@ public:
 
 
 #if HAVE_BOEHMGC
-typedef list<DrvInfo, traceable_allocator<DrvInfo> > DrvInfos;
+typedef std::list<DrvInfo, traceable_allocator<DrvInfo> > DrvInfos;
 #else
-typedef list<DrvInfo> DrvInfos;
+typedef std::list<DrvInfo> DrvInfos;
 #endif
 
 
@@ -81,7 +81,7 @@ typedef list<DrvInfo> DrvInfos;
 std::optional<DrvInfo> getDerivation(EvalState & state,
     Value & v, bool ignoreAssertionFailures);
 
-void getDerivations(EvalState & state, Value & v, const string & pathPrefix,
+void getDerivations(EvalState & state, Value & v, const std::string & pathPrefix,
     Bindings & autoArgs, DrvInfos & drvs,
     bool ignoreAssertionFailures);
 

src/libexpr/json-to-value.cc

@@ -163,7 +163,7 @@ public:
     }
 };
 
-void parseJSON(EvalState & state, const string & s_, Value & v)
+void parseJSON(EvalState & state, const std::string_view & s_, Value & v)
 {
     JSONSax parser(state, v);
     bool res = json::sax_parse(s_, &parser);

src/libexpr/json-to-value.hh

@@ -8,6 +8,6 @@ namespace nix {
 
 MakeError(JSONParseError, EvalError);
 
-void parseJSON(EvalState & state, const string & s, Value & v);
+void parseJSON(EvalState & state, const std::string_view & s, Value & v);
 
 }

src/libexpr/lexer.l

@@ -64,29 +64,32 @@ static void adjustLoc(YYLTYPE * loc, const char * s, size_t len)
 }
 
 
-// FIXME: optimize
-static Expr * unescapeStr(SymbolTable & symbols, const char * s, size_t length)
+// we make use of the fact that the parser receives a private copy of the input
+// string and can munge around in it.
+static StringToken unescapeStr(SymbolTable & symbols, char * s, size_t length)
 {
-    string t;
-    t.reserve(length);
+    char * result = s;
+    char * t = s;
     char c;
+    // the input string is terminated with *two* NULs, so we can safely take
+    // *one* character after the one being checked against.
     while ((c = *s++)) {
         if (c == '\\') {
-            assert(*s);
             c = *s++;
-            if (c == 'n') t += '\n';
-            else if (c == 'r') t += '\r';
-            else if (c == 't') t += '\t';
-            else t += c;
+            if (c == 'n') *t = '\n';
+            else if (c == 'r') *t = '\r';
+            else if (c == 't') *t = '\t';
+            else *t = c;
         }
         else if (c == '\r') {
             /* Normalise CR and CR/LF into LF. */
-            t += '\n';
+            *t = '\n';
             if (*s == '\n') s++; /* cr/lf */
         }
-        else t += c;
+        else *t = c;
+        t++;
     }
-    return new ExprString(symbols.create(t));
+    return {result, size_t(t - result)};
 }
 
 
@@ -139,7 +142,7 @@ or          { return OR_KW; }
 \/\/        { return UPDATE; }
 \+\+        { return CONCAT; }
 
-{ID}        { yylval->id = strdup(yytext); return ID; }
+{ID}        { yylval->id = {yytext, (size_t) yyleng}; return ID; }
 {INT}       { errno = 0;
               try {
                   yylval->n = boost::lexical_cast<int64_t>(yytext);
@@ -173,7 +176,7 @@ or          { return OR_KW; }
                 /* It is impossible to match strings ending with '$' with one
                    regex because trailing contexts are only valid at the end
                    of a rule. (A sane but undocumented limitation.) */
-                yylval->e = unescapeStr(data->symbols, yytext, yyleng);
+                yylval->str = unescapeStr(data->symbols, yytext, yyleng);
                 return STR;
               }
 <STRING>\$\{  { PUSH_STATE(DEFAULT); return DOLLAR_CURLY; }
@@ -188,26 +191,26 @@ or          { return OR_KW; }
 
 \'\'(\ *\n)?     { PUSH_STATE(IND_STRING); return IND_STRING_OPEN; }
 <IND_STRING>([^\$\']|\$[^\{\']|\'[^\'\$])+ {
-                   yylval->e = new ExprIndStr(yytext);
+                   yylval->str = {yytext, (size_t) yyleng, true};
                    return IND_STR;
                  }
 <IND_STRING>\'\'\$ |
 <IND_STRING>\$   {
-                   yylval->e = new ExprIndStr("$");
+                   yylval->str = {"$", 1};
                    return IND_STR;
                  }
 <IND_STRING>\'\'\' {
-                   yylval->e = new ExprIndStr("''");
+                   yylval->str = {"''", 2};
                    return IND_STR;
                  }
 <IND_STRING>\'\'\\{ANY} {
-                   yylval->e = unescapeStr(data->symbols, yytext + 2, yyleng - 2);
+                   yylval->str = unescapeStr(data->symbols, yytext + 2, yyleng - 2);
                    return IND_STR;
                  }
 <IND_STRING>\$\{ { PUSH_STATE(DEFAULT); return DOLLAR_CURLY; }
 <IND_STRING>\'\' { POP_STATE(); return IND_STRING_CLOSE; }
 <IND_STRING>\'   {
-                   yylval->e = new ExprIndStr("'");
+                   yylval->str = {"'", 1};
                    return IND_STR;
                  }
 
@@ -221,14 +224,14 @@ or          { return OR_KW; }
 <PATH_START>{PATH_SEG} {
   POP_STATE();
   PUSH_STATE(INPATH_SLASH);
-  yylval->path = strdup(yytext);
+  yylval->path = {yytext, (size_t) yyleng};
   return PATH;
 }
 
 <PATH_START>{HPATH_START} {
   POP_STATE();
   PUSH_STATE(INPATH_SLASH);
-  yylval->path = strdup(yytext);
+  yylval->path = {yytext, (size_t) yyleng};
   return HPATH;
 }
 
@@ -237,7 +240,7 @@ or          { return OR_KW; }
     PUSH_STATE(INPATH_SLASH);
   else
     PUSH_STATE(INPATH);
-  yylval->path = strdup(yytext);
+  yylval->path = {yytext, (size_t) yyleng};
   return PATH;
 }
 {HPATH} {
@@ -245,7 +248,7 @@ or          { return OR_KW; }
     PUSH_STATE(INPATH_SLASH);
   else
     PUSH_STATE(INPATH);
-  yylval->path = strdup(yytext);
+  yylval->path = {yytext, (size_t) yyleng};
   return HPATH;
 }
 
@@ -261,7 +264,7 @@ or          { return OR_KW; }
       PUSH_STATE(INPATH_SLASH);
   else
       PUSH_STATE(INPATH);
-  yylval->e = new ExprString(data->symbols.create(string(yytext)));
+  yylval->str = {yytext, (size_t) yyleng};
   return STR;
 }
 <INPATH>{ANY} |
@@ -280,8 +283,8 @@ or          { return OR_KW; }
   throw ParseError("path has a trailing slash");
 }
 
-{SPATH}     { yylval->path = strdup(yytext); return SPATH; }
-{URI}       { yylval->uri = strdup(yytext); return URI; }
+{SPATH}     { yylval->path = {yytext, (size_t) yyleng}; return SPATH; }
+{URI}       { yylval->uri = {yytext, (size_t) yyleng}; return URI; }
 
 [ \t\r\n]+    /* eat up whitespace */
 \#[^\r\n]*    /* single-line comments */

src/libexpr/nixexpr.cc

@@ -16,10 +16,10 @@ std::ostream & operator << (std::ostream & str, const Expr & e)
     return str;
 }
 
-static void showString(std::ostream & str, const string & s)
+static void showString(std::ostream & str, std::string_view s)
 {
     str << '"';
-    for (auto c : (string) s)
+    for (auto c : s)
         if (c == '"' || c == '\\' || c == '$') str << "\\" << c;
         else if (c == '\n') str << "\\n";
         else if (c == '\r') str << "\\r";
@@ -28,7 +28,7 @@ static void showString(std::ostream & str, const string & s)
     str << '"';
 }
 
-static void showId(std::ostream & str, const string & s)
+static void showId(std::ostream & str, std::string_view s)
 {
     if (s.empty())
         str << "\"\"";
@@ -103,11 +103,18 @@ void ExprAttrs::show(std::ostream & str) const
 {
     if (recursive) str << "rec ";
     str << "{ ";
-    for (auto & i : attrs)
-        if (i.second.inherited)
-            str << "inherit " << i.first << " " << "; ";
+    typedef const decltype(attrs)::value_type * Attr;
+    std::vector<Attr> sorted;
+    for (auto & i : attrs) sorted.push_back(&i);
+        std::sort(sorted.begin(), sorted.end(), [](Attr a, Attr b) {
+            return (const std::string &) a->first < (const std::string &) b->first;
+        });
+    for (auto & i : sorted) {
+        if (i->second.inherited)
+            str << "inherit " << i->first << " " << "; ";
         else
-            str << i.first << " = " << *i.second.e << "; ";
+            str << i->first << " = " << *i->second.e << "; ";
+    }
     for (auto & i : dynamicAttrs)
         str << "\"${" << *i.nameExpr << "}\" = " << *i.valueExpr << "; ";
     str << "}";
@@ -191,7 +198,7 @@ void ExprConcatStrings::show(std::ostream & str) const
     str << "(";
     for (auto & i : *es) {
         if (first) first = false; else str << " + ";
-        str << i.second;
+        str << *i.second;
     }
     str << ")";
 }
@@ -211,7 +218,7 @@ std::ostream & operator << (std::ostream & str, const Pos & pos)
         auto f = format(ANSI_BOLD "%1%" ANSI_NORMAL ":%2%:%3%");
         switch (pos.origin) {
             case foFile:
-                f % (string) pos.file;
+                f % (const std::string &) pos.file;
                 break;
             case foStdin:
             case foString:
@@ -227,7 +234,7 @@ std::ostream & operator << (std::ostream & str, const Pos & pos)
 }
 
 
-string showAttrPath(const AttrPath & attrPath)
+std::string showAttrPath(const AttrPath & attrPath)
 {
     std::ostringstream out;
     bool first = true;
@@ -461,9 +468,9 @@ void ExprLambda::setName(Symbol & name)
 }
 
 
-string ExprLambda::showNamePos() const
+std::string ExprLambda::showNamePos() const
 {
-    return (format("%1% at %2%") % (name.set() ? "'" + (string) name + "'" : "anonymous function") % pos).str();
+    return fmt("%1% at %2%", name.set() ? "'" + (std::string) name + "'" : "anonymous function", pos);
 }
 
 
@@ -473,7 +480,7 @@ string ExprLambda::showNamePos() const
 size_t SymbolTable::totalSize() const
 {
     size_t n = 0;
-    for (auto & i : symbols)
+    for (auto & i : store)
         n += i.size();
     return n;
 }

src/libexpr/nixexpr.hh

@@ -26,18 +26,21 @@ struct Pos
     FileOrigin origin;
     Symbol file;
     unsigned int line, column;
-    Pos() : origin(foString), line(0), column(0) { };
+
+    Pos() : origin(foString), line(0), column(0) { }
     Pos(FileOrigin origin, const Symbol & file, unsigned int line, unsigned int column)
-        : origin(origin), file(file), line(line), column(column) { };
+        : origin(origin), file(file), line(line), column(column) { }
+
     operator bool() const
     {
         return line != 0;
     }
+
     bool operator < (const Pos & p2) const
     {
         if (!line) return p2.line;
         if (!p2.line) return false;
-        int d = ((string) file).compare((string) p2.file);
+        int d = ((const std::string &) file).compare((const std::string &) p2.file);
         if (d < 0) return true;
         if (d > 0) return false;
         if (line < p2.line) return true;
@@ -68,7 +71,7 @@ struct AttrName
 
 typedef std::vector<AttrName> AttrPath;
 
-string showAttrPath(const AttrPath & attrPath);
+std::string showAttrPath(const AttrPath & attrPath);
 
 
 /* Abstract syntax of Nix expressions. */
@@ -110,25 +113,18 @@ struct ExprFloat : Expr
 
 struct ExprString : Expr
 {
-    Symbol s;
+    std::string s;
     Value v;
-    ExprString(const Symbol & s) : s(s) { v.mkString(s); };
+    ExprString(std::string s) : s(std::move(s)) { v.mkString(this->s.data()); };
     COMMON_METHODS
     Value * maybeThunk(EvalState & state, Env & env);
 };
 
-/* Temporary class used during parsing of indented strings. */
-struct ExprIndStr : Expr
-{
-    string s;
-    ExprIndStr(const string & s) : s(s) { };
-};
-
 struct ExprPath : Expr
 {
-    string s;
+    std::string s;
     Value v;
-    ExprPath(const string & s) : s(s) { v.mkPath(this->s.c_str()); };
+    ExprPath(std::string s) : s(std::move(s)) { v.mkPath(this->s.c_str()); };
     COMMON_METHODS
     Value * maybeThunk(EvalState & state, Env & env);
 };
@@ -223,10 +219,25 @@ struct Formal
 
 struct Formals
 {
-    typedef std::list<Formal> Formals_;
+    typedef std::vector<Formal> Formals_;
     Formals_ formals;
-    std::set<Symbol> argNames; // used during parsing
     bool ellipsis;
+
+    bool has(Symbol arg) const {
+        auto it = std::lower_bound(formals.begin(), formals.end(), arg,
+            [] (const Formal & f, const Symbol & sym) { return f.name < sym; });
+        return it != formals.end() && it->name == arg;
+    }
+
+    std::vector<Formal> lexicographicOrder() const
+    {
+        std::vector<Formal> result(formals.begin(), formals.end());
+        std::sort(result.begin(), result.end(),
+            [] (const Formal & a, const Formal & b) {
+                return std::string_view(a.name) < std::string_view(b.name);
+            });
+        return result;
+    }
 };
 
 struct ExprLambda : Expr
@@ -239,14 +250,9 @@ struct ExprLambda : Expr
     ExprLambda(const Pos & pos, const Symbol & arg, Formals * formals, Expr * body)
         : pos(pos), arg(arg), formals(formals), body(body)
     {
-        if (!arg.empty() && formals && formals->argNames.find(arg) != formals->argNames.end())
-            throw ParseError({
-                .msg = hintfmt("duplicate formal function argument '%1%'", arg),
-                .errPos = pos
-            });
     };
     void setName(Symbol & name);
-    string showNamePos() const;
+    std::string showNamePos() const;
     inline bool hasFormals() const { return formals != nullptr; }
     COMMON_METHODS
 };
@@ -332,8 +338,8 @@ struct ExprConcatStrings : Expr
 {
     Pos pos;
     bool forceString;
-    vector<std::pair<Pos, Expr *> > * es;
-    ExprConcatStrings(const Pos & pos, bool forceString, vector<std::pair<Pos, Expr *> > * es)
+    std::vector<std::pair<Pos, Expr *> > * es;
+    ExprConcatStrings(const Pos & pos, bool forceString, std::vector<std::pair<Pos, Expr *> > * es)
         : pos(pos), forceString(forceString), es(es) { };
     COMMON_METHODS
 };
@@ -364,15 +370,19 @@ struct StaticEnv
 
     void sort()
     {
-        std::sort(vars.begin(), vars.end(),
+        std::stable_sort(vars.begin(), vars.end(),
             [](const Vars::value_type & a, const Vars::value_type & b) { return a.first < b.first; });
     }
 
     void deduplicate()
     {
-        const auto last = std::unique(vars.begin(), vars.end(),
-            [] (const Vars::value_type & a, const Vars::value_type & b) { return a.first == b.first; });
-        vars.erase(last, vars.end());
+        auto it = vars.begin(), jt = it, end = vars.end();
+        while (jt != end) {
+            *it = *jt++;
+            while (jt != end && it->first == jt->first) *it = *jt++;
+            it++;
+        }
+        vars.erase(it, end);
     }
 
     Vars::const_iterator find(const Symbol & name) const

src/libexpr/parser.y

@@ -16,6 +16,8 @@
 #ifndef BISON_HEADER
 #define BISON_HEADER
 
+#include <variant>
+
 #include "util.hh"
 
 #include "nixexpr.hh"
@@ -39,8 +41,22 @@ namespace nix {
             { };
     };
 
+    struct ParserFormals {
+        std::vector<Formal> formals;
+        bool ellipsis = false;
+    };
+
 }
 
+// using C a struct allows us to avoid having to define the special
+// members that using string_view here would implicitly delete.
+struct StringToken {
+  const char * p;
+  size_t l;
+  bool hasIndentation;
+  operator std::string_view() const { return {p, l}; }
+};
+
 #define YY_DECL int yylex \
     (YYSTYPE * yylval_param, YYLTYPE * yylloc_param, yyscan_t yyscanner, nix::ParseData * data)
 
@@ -140,21 +156,46 @@ static void addAttr(ExprAttrs * attrs, AttrPath & attrPath,
 }
 
 
-static void addFormal(const Pos & pos, Formals * formals, const Formal & formal)
+static Formals * toFormals(ParseData & data, ParserFormals * formals,
+    Pos pos = noPos, Symbol arg = {})
 {
-    if (!formals->argNames.insert(formal.name).second)
+    std::sort(formals->formals.begin(), formals->formals.end(),
+        [] (const auto & a, const auto & b) {
+            return std::tie(a.name, a.pos) < std::tie(b.name, b.pos);
+        });
+
+    std::optional<std::pair<Symbol, Pos>> duplicate;
+    for (size_t i = 0; i + 1 < formals->formals.size(); i++) {
+        if (formals->formals[i].name != formals->formals[i + 1].name)
+            continue;
+        std::pair thisDup{formals->formals[i].name, formals->formals[i + 1].pos};
+        duplicate = std::min(thisDup, duplicate.value_or(thisDup));
+    }
+    if (duplicate)
         throw ParseError({
-            .msg = hintfmt("duplicate formal function argument '%1%'",
-                formal.name),
+            .msg = hintfmt("duplicate formal function argument '%1%'", duplicate->first),
+            .errPos = duplicate->second
+        });
+
+    Formals result;
+    result.ellipsis = formals->ellipsis;
+    result.formals = std::move(formals->formals);
+
+    if (arg.set() && result.has(arg))
+        throw ParseError({
+            .msg = hintfmt("duplicate formal function argument '%1%'", arg),
             .errPos = pos
         });
-    formals->formals.push_front(formal);
+
+    delete formals;
+    return new Formals(std::move(result));
 }
 
 
-static Expr * stripIndentation(const Pos & pos, SymbolTable & symbols, vector<std::pair<Pos, Expr *> > & es)
+static Expr * stripIndentation(const Pos & pos, SymbolTable & symbols,
+    std::vector<std::pair<Pos, std::variant<Expr *, StringToken> > > & es)
 {
-    if (es.empty()) return new ExprString(symbols.create(""));
+    if (es.empty()) return new ExprString("");
 
     /* Figure out the minimum indentation.  Note that by design
        whitespace-only final lines are not taken into account.  (So
@@ -163,20 +204,20 @@ static Expr * stripIndentation(const Pos & pos, SymbolTable & symbols, vector<st
     size_t minIndent = 1000000;
     size_t curIndent = 0;
     for (auto & [i_pos, i] : es) {
-        ExprIndStr * e = dynamic_cast<ExprIndStr *>(i);
-        if (!e) {
-            /* Anti-quotations end the current start-of-line whitespace. */
+        auto * str = std::get_if<StringToken>(&i);
+        if (!str || !str->hasIndentation) {
+            /* Anti-quotations and escaped characters end the current start-of-line whitespace. */
             if (atStartOfLine) {
                 atStartOfLine = false;
                 if (curIndent < minIndent) minIndent = curIndent;
             }
             continue;
         }
-        for (size_t j = 0; j < e->s.size(); ++j) {
+        for (size_t j = 0; j < str->l; ++j) {
             if (atStartOfLine) {
-                if (e->s[j] == ' ')
+                if (str->p[j] == ' ')
                     curIndent++;
-                else if (e->s[j] == '\n') {
+                else if (str->p[j] == '\n') {
                     /* Empty line, doesn't influence minimum
                        indentation. */
                     curIndent = 0;
@@ -184,7 +225,7 @@ static Expr * stripIndentation(const Pos & pos, SymbolTable & symbols, vector<st
                     atStartOfLine = false;
                     if (curIndent < minIndent) minIndent = curIndent;
                 }
-            } else if (e->s[j] == '\n') {
+            } else if (str->p[j] == '\n') {
                 atStartOfLine = true;
                 curIndent = 0;
             }
@@ -192,49 +233,50 @@ static Expr * stripIndentation(const Pos & pos, SymbolTable & symbols, vector<st
     }
 
     /* Strip spaces from each line. */
-    vector<std::pair<Pos, Expr *> > * es2 = new vector<std::pair<Pos, Expr *> >;
+    std::vector<std::pair<Pos, Expr *> > * es2 = new std::vector<std::pair<Pos, Expr *> >;
     atStartOfLine = true;
     size_t curDropped = 0;
     size_t n = es.size();
-    for (vector<std::pair<Pos, Expr *> >::iterator i = es.begin(); i != es.end(); ++i, --n) {
-        ExprIndStr * e = dynamic_cast<ExprIndStr *>(i->second);
-        if (!e) {
+    auto i = es.begin();
+    const auto trimExpr = [&] (Expr * e) {
         atStartOfLine = false;
         curDropped = 0;
-            es2->push_back(*i);
-            continue;
-        }
-
-        string s2;
-        for (size_t j = 0; j < e->s.size(); ++j) {
+        es2->emplace_back(i->first, e);
+    };
+    const auto trimString = [&] (const StringToken & t) {
+        std::string s2;
+        for (size_t j = 0; j < t.l; ++j) {
             if (atStartOfLine) {
-                if (e->s[j] == ' ') {
+                if (t.p[j] == ' ') {
                     if (curDropped++ >= minIndent)
-                        s2 += e->s[j];
+                        s2 += t.p[j];
                 }
-                else if (e->s[j] == '\n') {
+                else if (t.p[j] == '\n') {
                     curDropped = 0;
-                    s2 += e->s[j];
+                    s2 += t.p[j];
                 } else {
                     atStartOfLine = false;
                     curDropped = 0;
-                    s2 += e->s[j];
+                    s2 += t.p[j];
                 }
             } else {
-                s2 += e->s[j];
-                if (e->s[j] == '\n') atStartOfLine = true;
+                s2 += t.p[j];
+                if (t.p[j] == '\n') atStartOfLine = true;
             }
         }
 
         /* Remove the last line if it is empty and consists only of
            spaces. */
         if (n == 1) {
-            string::size_type p = s2.find_last_of('\n');
-            if (p != string::npos && s2.find_first_not_of(' ', p + 1) == string::npos)
-                s2 = string(s2, 0, p + 1);
+            std::string::size_type p = s2.find_last_of('\n');
+            if (p != std::string::npos && s2.find_first_not_of(' ', p + 1) == std::string::npos)
+                s2 = std::string(s2, 0, p + 1);
         }
 
-        es2->emplace_back(i->first, new ExprString(symbols.create(s2)));
+        es2->emplace_back(i->first, new ExprString(s2));
+    };
+    for (; i != es.end(); ++i, --n) {
+        std::visit(overloaded { trimExpr, trimString }, i->second);
     }
 
     /* If this is a single string, then don't do a concatenation. */
@@ -269,15 +311,17 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
   nix::Expr * e;
   nix::ExprList * list;
   nix::ExprAttrs * attrs;
-  nix::Formals * formals;
+  nix::ParserFormals * formals;
   nix::Formal * formal;
   nix::NixInt n;
   nix::NixFloat nf;
-  const char * id; // !!! -> Symbol
-  char * path;
-  char * uri;
+  StringToken id; // !!! -> Symbol
+  StringToken path;
+  StringToken uri;
+  StringToken str;
   std::vector<nix::AttrName> * attrNames;
   std::vector<std::pair<nix::Pos, nix::Expr *> > * string_parts;
+  std::vector<std::pair<nix::Pos, std::variant<nix::Expr *, StringToken> > > * ind_string_parts;
 }
 
 %type <e> start expr expr_function expr_if expr_op
@@ -287,11 +331,12 @@ void yyerror(YYLTYPE * loc, yyscan_t scanner, ParseData * data, const char * err
 %type <formals> formals
 %type <formal> formal
 %type <attrNames> attrs attrpath
-%type <string_parts> string_parts_interpolated ind_string_parts
+%type <string_parts> string_parts_interpolated
+%type <ind_string_parts> ind_string_parts
 %type <e> path_start string_parts string_attr
 %type <id> attr
 %token <id> ID ATTRPATH
-%token <e> STR IND_STR
+%token <str> STR IND_STR
 %token <n> INT
 %token <nf> FLOAT
 %token <path> PATH HPATH SPATH PATH_END
@@ -324,11 +369,17 @@ expr_function
   : ID ':' expr_function
     { $$ = new ExprLambda(CUR_POS, data->symbols.create($1), 0, $3); }
   | '{' formals '}' ':' expr_function
-    { $$ = new ExprLambda(CUR_POS, data->symbols.create(""), $2, $5); }
+    { $$ = new ExprLambda(CUR_POS, data->symbols.create(""), toFormals(*data, $2), $5); }
   | '{' formals '}' '@' ID ':' expr_function
-    { $$ = new ExprLambda(CUR_POS, data->symbols.create($5), $2, $7); }
+    {
+      Symbol arg = data->symbols.create($5);
+      $$ = new ExprLambda(CUR_POS, arg, toFormals(*data, $2, CUR_POS, arg), $7);
+    }
   | ID '@' '{' formals '}' ':' expr_function
-    { $$ = new ExprLambda(CUR_POS, data->symbols.create($1), $4, $7); }
+    {
+      Symbol arg = data->symbols.create($1);
+      $$ = new ExprLambda(CUR_POS, arg, toFormals(*data, $4, CUR_POS, arg), $7);
+    }
   | ASSERT expr ';' expr_function
     { $$ = new ExprAssert(CUR_POS, $2, $4); }
   | WITH expr ';' expr_function
@@ -364,7 +415,7 @@ expr_op
   | expr_op UPDATE expr_op { $$ = new ExprOpUpdate(CUR_POS, $1, $3); }
   | expr_op '?' attrpath { $$ = new ExprOpHasAttr($1, *$3); }
   | expr_op '+' expr_op
-    { $$ = new ExprConcatStrings(CUR_POS, false, new vector<std::pair<Pos, Expr *> >({{makeCurPos(@1, data), $1}, {makeCurPos(@3, data), $3}})); }
+    { $$ = new ExprConcatStrings(CUR_POS, false, new std::vector<std::pair<Pos, Expr *> >({{makeCurPos(@1, data), $1}, {makeCurPos(@3, data), $3}})); }
   | expr_op '-' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__sub")), {$1, $3}); }
   | expr_op '*' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__mul")), {$1, $3}); }
   | expr_op '/' expr_op { $$ = new ExprCall(CUR_POS, new ExprVar(data->symbols.create("__div")), {$1, $3}); }
@@ -397,7 +448,8 @@ expr_select
 
 expr_simple
   : ID {
-      if (strcmp($1, "__curPos") == 0)
+      std::string_view s = "__curPos";
+      if ($1.l == s.size() && strncmp($1.p, s.data(), s.size()) == 0)
           $$ = new ExprPos(CUR_POS);
       else
           $$ = new ExprVar(CUR_POS, data->symbols.create($1));
@@ -414,11 +466,11 @@ expr_simple
       $$ = new ExprConcatStrings(CUR_POS, false, $2);
   }
   | SPATH {
-      string path($1 + 1, strlen($1) - 2);
+      std::string path($1.p + 1, $1.l - 2);
       $$ = new ExprCall(CUR_POS,
           new ExprVar(data->symbols.create("__findFile")),
           {new ExprVar(data->symbols.create("__nixPath")),
-           new ExprString(data->symbols.create(path))});
+           new ExprString(path)});
   }
   | URI {
       static bool noURLLiterals = settings.isExperimentalFeatureEnabled(Xp::NoUrlLiterals);
@@ -427,7 +479,7 @@ expr_simple
               .msg = hintfmt("URL literals are disabled"),
               .errPos = CUR_POS
           });
-      $$ = new ExprString(data->symbols.create($1));
+      $$ = new ExprString(std::string($1));
   }
   | '(' expr ')' { $$ = $2; }
   /* Let expressions `let {..., body = ...}' are just desugared
@@ -442,32 +494,33 @@ expr_simple
   ;
 
 string_parts
-  : STR
+  : STR { $$ = new ExprString(std::string($1)); }
   | string_parts_interpolated { $$ = new ExprConcatStrings(CUR_POS, true, $1); }
-  | { $$ = new ExprString(data->symbols.create("")); }
+  | { $$ = new ExprString(""); }
   ;
 
 string_parts_interpolated
-  : string_parts_interpolated STR { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $2); }
+  : string_parts_interpolated STR
+  { $$ = $1; $1->emplace_back(makeCurPos(@2, data), new ExprString(std::string($2))); }
   | string_parts_interpolated DOLLAR_CURLY expr '}' { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $3); }
-  | DOLLAR_CURLY expr '}' { $$ = new vector<std::pair<Pos, Expr *> >; $$->emplace_back(makeCurPos(@1, data), $2); }
+  | DOLLAR_CURLY expr '}' { $$ = new std::vector<std::pair<Pos, Expr *> >; $$->emplace_back(makeCurPos(@1, data), $2); }
   | STR DOLLAR_CURLY expr '}' {
-      $$ = new vector<std::pair<Pos, Expr *> >;
-      $$->emplace_back(makeCurPos(@1, data), $1);
+      $$ = new std::vector<std::pair<Pos, Expr *> >;
+      $$->emplace_back(makeCurPos(@1, data), new ExprString(std::string($1)));
       $$->emplace_back(makeCurPos(@2, data), $3);
     }
   ;
 
 path_start
   : PATH {
-    Path path(absPath($1, data->basePath));
+    Path path(absPath({$1.p, $1.l}, data->basePath));
     /* add back in the trailing '/' to the first segment */
-    if ($1[strlen($1)-1] == '/' && strlen($1) > 1)
+    if ($1.p[$1.l-1] == '/' && $1.l > 1)
       path += "/";
     $$ = new ExprPath(path);
   }
   | HPATH {
-    Path path(getHome() + string($1 + 1));
+    Path path(getHome() + std::string($1.p + 1, $1.l - 1));
     $$ = new ExprPath(path);
   }
   ;
@@ -475,7 +528,7 @@ path_start
 ind_string_parts
   : ind_string_parts IND_STR { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $2); }
   | ind_string_parts DOLLAR_CURLY expr '}' { $$ = $1; $1->emplace_back(makeCurPos(@2, data), $3); }
-  | { $$ = new vector<std::pair<Pos, Expr *> >; }
+  | { $$ = new std::vector<std::pair<Pos, std::variant<Expr *, StringToken> > >; }
   ;
 
 binds
@@ -507,7 +560,7 @@ attrs
     { $$ = $1;
       ExprString * str = dynamic_cast<ExprString *>($2);
       if (str) {
-          $$->push_back(AttrName(str->s));
+          $$->push_back(AttrName(data->symbols.create(str->s)));
           delete str;
       } else
           throw ParseError({
@@ -524,17 +577,17 @@ attrpath
     { $$ = $1;
       ExprString * str = dynamic_cast<ExprString *>($3);
       if (str) {
-          $$->push_back(AttrName(str->s));
+          $$->push_back(AttrName(data->symbols.create(str->s)));
           delete str;
       } else
           $$->push_back(AttrName($3));
     }
-  | attr { $$ = new vector<AttrName>; $$->push_back(AttrName(data->symbols.create($1))); }
+  | attr { $$ = new std::vector<AttrName>; $$->push_back(AttrName(data->symbols.create($1))); }
   | string_attr
-    { $$ = new vector<AttrName>;
+    { $$ = new std::vector<AttrName>;
       ExprString *str = dynamic_cast<ExprString *>($1);
       if (str) {
-          $$->push_back(AttrName(str->s));
+          $$->push_back(AttrName(data->symbols.create(str->s)));
           delete str;
       } else
           $$->push_back(AttrName($1));
@@ -543,7 +596,7 @@ attrpath
 
 attr
   : ID { $$ = $1; }
-  | OR_KW { $$ = "or"; }
+  | OR_KW { $$ = {"or", 2}; }
   ;
 
 string_attr
@@ -558,13 +611,13 @@ expr_list
 
 formals
   : formal ',' formals
-    { $$ = $3; addFormal(CUR_POS, $$, *$1); }
+    { $$ = $3; $$->formals.push_back(*$1); }
   | formal
-    { $$ = new Formals; addFormal(CUR_POS, $$, *$1); $$->ellipsis = false; }
+    { $$ = new ParserFormals; $$->formals.push_back(*$1); $$->ellipsis = false; }
   |
-    { $$ = new Formals; $$->ellipsis = false; }
+    { $$ = new ParserFormals; $$->ellipsis = false; }
   | ELLIPSIS
-    { $$ = new Formals; $$->ellipsis = true; }
+    { $$ = new ParserFormals; $$->ellipsis = true; }
   ;
 
 formal
@@ -589,8 +642,8 @@ formal
 namespace nix {
 
 
-Expr * EvalState::parse(const char * text, FileOrigin origin,
-    const Path & path, const Path & basePath, StaticEnv & staticEnv)
+Expr * EvalState::parse(char * text, size_t length, FileOrigin origin,
+    const PathView path, const PathView basePath, StaticEnv & staticEnv)
 {
     yyscan_t scanner;
     ParseData data(*this);
@@ -609,7 +662,7 @@ Expr * EvalState::parse(const char * text, FileOrigin origin,
     data.basePath = basePath;
 
     yylex_init(&scanner);
-    yy_scan_string(text, scanner);
+    yy_scan_buffer(text, length, scanner);
     int res = yyparse(scanner, &data);
     yylex_destroy(scanner);
 
@@ -655,63 +708,70 @@ Expr * EvalState::parseExprFromFile(const Path & path)
 
 Expr * EvalState::parseExprFromFile(const Path & path, StaticEnv & staticEnv)
 {
-    return parse(readFile(path).c_str(), foFile, path, dirOf(path), staticEnv);
+    auto buffer = readFile(path);
+    // readFile should have left some extra space for terminators
+    buffer.append("\0\0", 2);
+    return parse(buffer.data(), buffer.size(), foFile, path, dirOf(path), staticEnv);
 }
 
 
-Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath, StaticEnv & staticEnv)
+Expr * EvalState::parseExprFromString(std::string s, const Path & basePath, StaticEnv & staticEnv)
 {
-    return parse(s.data(), foString, "", basePath, staticEnv);
+    s.append("\0\0", 2);
+    return parse(s.data(), s.size(), foString, "", basePath, staticEnv);
 }
 
 
-Expr * EvalState::parseExprFromString(std::string_view s, const Path & basePath)
+Expr * EvalState::parseExprFromString(std::string s, const Path & basePath)
 {
-    return parseExprFromString(s, basePath, staticBaseEnv);
+    return parseExprFromString(std::move(s), basePath, staticBaseEnv);
 }
 
 
 Expr * EvalState::parseStdin()
 {
     //Activity act(*logger, lvlTalkative, format("parsing standard input"));
-    return parse(drainFD(0).data(), foStdin, "", absPath("."), staticBaseEnv);
+    auto buffer = drainFD(0);
+    // drainFD should have left some extra space for terminators
+    buffer.append("\0\0", 2);
+    return parse(buffer.data(), buffer.size(), foStdin, "", absPath("."), staticBaseEnv);
 }
 
 
-void EvalState::addToSearchPath(const string & s)
+void EvalState::addToSearchPath(const std::string & s)
 {
     size_t pos = s.find('=');
-    string prefix;
+    std::string prefix;
     Path path;
-    if (pos == string::npos) {
+    if (pos == std::string::npos) {
         path = s;
     } else {
-        prefix = string(s, 0, pos);
-        path = string(s, pos + 1);
+        prefix = std::string(s, 0, pos);
+        path = std::string(s, pos + 1);
     }
 
     searchPath.emplace_back(prefix, path);
 }
 
 
-Path EvalState::findFile(const string & path)
+Path EvalState::findFile(const std::string_view path)
 {
     return findFile(searchPath, path);
 }
 
 
-Path EvalState::findFile(SearchPath & searchPath, const string & path, const Pos & pos)
+Path EvalState::findFile(SearchPath & searchPath, const std::string_view path, const Pos & pos)
 {
     for (auto & i : searchPath) {
         std::string suffix;
         if (i.first.empty())
-            suffix = "/" + path;
+            suffix = concatStrings("/", path);
         else {
             auto s = i.first.size();
             if (path.compare(0, s, i.first) != 0 ||
                 (path.size() > s && path[s] != '/'))
                 continue;
-            suffix = path.size() == s ? "" : "/" + string(path, s);
+            suffix = path.size() == s ? "" : concatStrings("/", path.substr(s));
         }
         auto r = resolveSearchPathElem(i);
         if (!r.first) continue;
@@ -720,7 +780,7 @@ Path EvalState::findFile(SearchPath & searchPath, const string & path, const Pos
     }
 
     if (hasPrefix(path, "nix/"))
-        return corepkgsPrefix + path.substr(4);
+        return concatStrings(corepkgsPrefix, path.substr(4));
 
     throw ThrownError({
         .msg = hintfmt(evalSettings.pureEval

src/libexpr/primops.cc

@@ -12,6 +12,8 @@
 #include "value-to-xml.hh"
 #include "primops.hh"
 
+#include <boost/container/small_vector.hpp>
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <unistd.h>
@@ -90,8 +92,6 @@ StringMap EvalState::realiseContext(const PathSet & context)
 }
 
 struct RealisePathFlags {
-    // Whether to check whether the path is a valid absolute path
-    bool requireAbsolutePath = true;
     // Whether to check that the path is allowed in pure eval mode
     bool checkForPureEval = true;
 };
@@ -100,10 +100,17 @@ static Path realisePath(EvalState & state, const Pos & pos, Value & v, const Rea
 {
     PathSet context;
 
-    Path path = flags.requireAbsolutePath
-        ? state.coerceToPath(pos, v, context)
-        : state.coerceToString(pos, v, context, false, false);
+    auto path = [&]()
+    {
+        try {
+            return state.coerceToPath(pos, v, context);
+        } catch (Error & e) {
+            e.addTrace(pos, "while realising the context of a path");
+            throw;
+        }
+    }();
 
+    try {
         StringMap rewrites = state.realiseContext(context);
 
         auto realPath = state.toRealPath(rewriteStrings(path, rewrites), context);
@@ -111,6 +118,10 @@ static Path realisePath(EvalState & state, const Pos & pos, Value & v, const Rea
         return flags.checkForPureEval
             ? state.checkSourcePath(realPath)
             : realPath;
+    } catch (Error & e) {
+        e.addTrace(pos, "while realising the context of path '%s'", path);
+        throw;
+    }
 }
 
 /* Add and attribute to the given attribute map from the output name to
@@ -130,7 +141,7 @@ static void mkOutputString(
     BindingsBuilder & attrs,
     const StorePath & drvPath,
     const BasicDerivation & drv,
-    const std::pair<string, DerivationOutput> & o)
+    const std::pair<std::string, DerivationOutput> & o)
 {
     auto optOutputPath = o.second.path(*state.store, drv.name, o.first);
     attrs.alloc(o.first).mkString(
@@ -148,18 +159,7 @@ static void mkOutputString(
    argument. */
 static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vScope, Value & v)
 {
-    Path path;
-    try {
-        path = realisePath(state, pos, vPath);
-    } catch (InvalidPathError & e) {
-        throw EvalError({
-            .msg = hintfmt("cannot import '%1%', since path '%2%' is not valid", path, e.path),
-            .errPos = pos
-        });
-    } catch (Error & e) {
-        e.addTrace(pos, "while importing '%s'", path);
-        throw;
-    }
+    auto path = realisePath(state, pos, vPath);
 
     // FIXME
     auto isValidDerivationInStore = [&]() -> std::optional<StorePath> {
@@ -210,7 +210,7 @@ static void import(EvalState & state, const Pos & pos, Value & vPath, Value * vS
         if (!vScope)
             state.evalFile(path, v);
         else {
-            state.forceAttrs(*vScope);
+            state.forceAttrs(*vScope, pos);
 
             Env * env = &state.allocEnv(vScope->attrs->size());
             env->up = &state.baseEnv;
@@ -312,20 +312,9 @@ extern "C" typedef void (*ValueInitializer)(EvalState & state, Value & v);
 /* Load a ValueInitializer from a DSO and return whatever it initializes */
 void prim_importNative(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    Path path;
-    try {
-        path = realisePath(state, pos, *args[0]);
-    } catch (InvalidPathError & e) {
-        throw EvalError({
-            .msg = hintfmt("cannot import '%1%', since path '%2%' is not valid", path, e.path),
-            .errPos = pos
-        });
-    } catch (Error & e) {
-        e.addTrace(pos, "while importing '%s'", path);
-        throw;
-    }
+    auto path = realisePath(state, pos, *args[0]);
 
-    string sym = state.forceStringNoCtx(*args[1], pos);
+    std::string sym(state.forceStringNoCtx(*args[1], pos));
 
     void *handle = dlopen(path.c_str(), RTLD_LAZY | RTLD_LOCAL);
     if (!handle)
@@ -361,10 +350,11 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
         });
     }
     PathSet context;
-    auto program = state.coerceToString(pos, *elems[0], context, false, false);
+    auto program = state.coerceToString(pos, *elems[0], context, false, false).toOwned();
     Strings commandArgs;
-    for (unsigned int i = 1; i < args[0]->listSize(); ++i)
-        commandArgs.emplace_back(state.coerceToString(pos, *elems[i], context, false, false));
+    for (unsigned int i = 1; i < args[0]->listSize(); ++i) {
+        commandArgs.push_back(state.coerceToString(pos, *elems[i], context, false, false).toOwned());
+    }
     try {
         auto _ = state.realiseContext(context); // FIXME: Handle CA derivations
     } catch (InvalidPathError & e) {
@@ -378,7 +368,7 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
     auto output = runProgram(program, true, commandArgs);
     Expr * parsed;
     try {
-        parsed = state.parseExprFromString(output, pos.file);
+        parsed = state.parseExprFromString(std::move(output), pos.file);
     } catch (Error & e) {
         e.addTrace(pos, "While parsing the output from '%1%'", program);
         throw;
@@ -396,7 +386,7 @@ void prim_exec(EvalState & state, const Pos & pos, Value * * args, Value & v)
 static void prim_typeOf(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     state.forceValue(*args[0], pos);
-    string t;
+    std::string t;
     switch (args[0]->type()) {
         case nInt: t = "int"; break;
         case nBool: t = "bool"; break;
@@ -584,24 +574,24 @@ struct CompareValues
 
 
 #if HAVE_BOEHMGC
-typedef list<Value *, gc_allocator<Value *> > ValueList;
+typedef std::list<Value *, gc_allocator<Value *> > ValueList;
 #else
-typedef list<Value *> ValueList;
+typedef std::list<Value *> ValueList;
 #endif
 
 
 static Bindings::iterator getAttr(
     EvalState & state,
-    string funcName,
-    string attrName,
+    std::string_view funcName,
+    Symbol attrSym,
     Bindings * attrSet,
     const Pos & pos)
 {
-    Bindings::iterator value = attrSet->find(state.symbols.create(attrName));
+    Bindings::iterator value = attrSet->find(attrSym);
     if (value == attrSet->end()) {
         hintformat errorMsg = hintfmt(
             "attribute '%s' missing for call to '%s'",
-            attrName,
+            attrSym,
             funcName
         );
 
@@ -635,7 +625,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
     Bindings::iterator startSet = getAttr(
         state,
         "genericClosure",
-        "startSet",
+        state.sStartSet,
         args[0]->attrs,
         pos
     );
@@ -650,7 +640,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
     Bindings::iterator op = getAttr(
         state,
         "genericClosure",
-        "operator",
+        state.sOperator,
         args[0]->attrs,
         pos
     );
@@ -664,7 +654,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
     // `doneKeys' doesn't need to be a GC root, because its values are
     // reachable from res.
     auto cmp = CompareValues(state);
-    set<Value *, decltype(cmp)> doneKeys(cmp);
+    std::set<Value *, decltype(cmp)> doneKeys(cmp);
     while (!workSet.empty()) {
         Value * e = *(workSet.begin());
         workSet.pop_front();
@@ -672,7 +662,7 @@ static void prim_genericClosure(EvalState & state, const Pos & pos, Value * * ar
         state.forceAttrs(*e, pos);
 
         Bindings::iterator key =
-            e->attrs->find(state.symbols.create("key"));
+            e->attrs->find(state.sKey);
         if (key == e->attrs->end())
             throw EvalError({
                 .msg = hintfmt("attribute 'key' required"),
@@ -717,7 +707,7 @@ static RegisterPrimOp primop_abort({
     .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
     {
         PathSet context;
-        string s = state.coerceToString(pos, *args[0], context);
+        auto s = state.coerceToString(pos, *args[0], context).toOwned();
         throw Abort("evaluation aborted with the following error message: '%1%'", s);
     }
 });
@@ -735,7 +725,7 @@ static RegisterPrimOp primop_throw({
     .fun = [](EvalState & state, const Pos & pos, Value * * args, Value & v)
     {
       PathSet context;
-      string s = state.coerceToString(pos, *args[0], context);
+      auto s = state.coerceToString(pos, *args[0], context).toOwned();
       throw ThrownError(s);
     }
 });
@@ -747,7 +737,7 @@ static void prim_addErrorContext(EvalState & state, const Pos & pos, Value * * a
         v = *args[1];
     } catch (Error & e) {
         PathSet context;
-        e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context));
+        e.addTrace(std::nullopt, state.coerceToString(pos, *args[0], context).toOwned());
         throw;
     }
 }
@@ -836,7 +826,7 @@ static RegisterPrimOp primop_tryEval({
 /* Return an environment variable.  Use with care. */
 static void prim_getEnv(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string name = state.forceStringNoCtx(*args[0], pos);
+    std::string name(state.forceStringNoCtx(*args[0], pos));
     v.mkString(evalSettings.restrictEval || evalSettings.pureEval ? "" : getEnv(name).value_or(""));
 }
 
@@ -945,7 +935,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
         pos
     );
 
-    string drvName;
+    std::string drvName;
     Pos & posDrvName(*attr->pos);
     try {
         drvName = state.forceStringNoCtx(*attr->value, pos);
@@ -983,10 +973,10 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
 
     for (auto & i : args[0]->attrs->lexicographicOrder()) {
         if (i->name == state.sIgnoreNulls) continue;
-        const string & key = i->name;
+        const std::string & key = i->name;
         vomit("processing attribute '%1%'", key);
 
-        auto handleHashMode = [&](const std::string & s) {
+        auto handleHashMode = [&](const std::string_view s) {
             if (s == "recursive") ingestionMethod = FileIngestionMethod::Recursive;
             else if (s == "flat") ingestionMethod = FileIngestionMethod::Flat;
             else
@@ -1041,7 +1031,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             else if (i->name == state.sArgs) {
                 state.forceList(*i->value, pos);
                 for (auto elem : i->value->listItems()) {
-                    string s = state.coerceToString(posDrvName, *elem, context, true);
+                    auto s = state.coerceToString(posDrvName, *elem, context, true).toOwned();
                     drv.args.push_back(s);
                 }
             }
@@ -1077,12 +1067,12 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
                     }
 
                 } else {
-                    auto s = state.coerceToString(*i->pos, *i->value, context, true);
+                    auto s = state.coerceToString(*i->pos, *i->value, context, true).toOwned();
                     drv.env.emplace(key, s);
-                    if (i->name == state.sBuilder) drv.builder = s;
-                    else if (i->name == state.sSystem) drv.platform = s;
-                    else if (i->name == state.sOutputHash) outputHash = s;
-                    else if (i->name == state.sOutputHashAlgo) outputHashAlgo = s;
+                    if (i->name == state.sBuilder) drv.builder = std::move(s);
+                    else if (i->name == state.sSystem) drv.platform = std::move(s);
+                    else if (i->name == state.sOutputHash) outputHash = std::move(s);
+                    else if (i->name == state.sOutputHashAlgo) outputHashAlgo = std::move(s);
                     else if (i->name == state.sOutputHashMode) handleHashMode(s);
                     else if (i->name == state.sOutputs)
                         handleOutputs(tokenizeString<Strings>(s));
@@ -1128,7 +1118,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
 
         /* Handle derivation outputs of the form ‘!<name>!<path>’. */
         else if (path.at(0) == '!') {
-            std::pair<string, string> ctx = decodeContext(path);
+            auto ctx = decodeContext(path);
             drv.inputDrvs[state.store->parseStorePath(ctx.first)].insert(ctx.second);
         }
 
@@ -1190,7 +1180,7 @@ static void prim_derivationStrict(EvalState & state, const Pos & pos, Value * *
             drv.outputs.insert_or_assign(i, DerivationOutput {
                 .output = DerivationOutputCAFloating {
                     .method = ingestionMethod,
-                    .hashType = std::move(ht),
+                    .hashType = ht,
                 },
             });
         }
@@ -1280,7 +1270,7 @@ static RegisterPrimOp primop_derivationStrict(RegisterPrimOp::Info {
    substituted by the corresponding output path at build time. For
    example, 'placeholder "out"' returns the string
    /1rz4g4znpzjwh1xymhjpm42vipw92pr73vdgl6xs1hycac8kf2n9. At build
-   time, any occurence of this string in an derivation attribute will
+   time, any occurrence of this string in an derivation attribute will
    be replaced with the concrete path in the Nix store of the output
    ‘out’. */
 static void prim_placeholder(EvalState & state, const Pos & pos, Value * * args, Value & v)
@@ -1377,22 +1367,12 @@ static RegisterPrimOp primop_storePath({
 
 static void prim_pathExists(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    Path path;
-    try {
-        // We don’t check the path right now, because we don’t want to throw if
-        // the path isn’t allowed, but just return false
-        // (and we can’t just catch the exception here because we still want to
-        // throw if something in the evaluation of `*args[0]` tries to access an
-        // unauthorized path)
-        path = realisePath(state, pos, *args[0], { .checkForPureEval = false });
-    } catch (InvalidPathError & e) {
-        throw EvalError({
-            .msg = hintfmt(
-                "cannot check the existence of '%1%', since path '%2%' is not valid",
-                path, e.path),
-            .errPos = pos
-        });
-    }
+    /* We don’t check the path right now, because we don’t want to
+      throw if the path isn’t allowed, but just return false (and we
+      can’t just catch the exception here because we still want to
+      throw if something in the evaluation of `*args[0]` tries to
+      access an unauthorized path). */
+    auto path = realisePath(state, pos, *args[0], { .checkForPureEval = false });
 
     try {
         v.mkBool(pathExists(state.checkSourcePath(path)));
@@ -1420,7 +1400,7 @@ static RegisterPrimOp primop_pathExists({
 static void prim_baseNameOf(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    v.mkString(baseNameOf(state.coerceToString(pos, *args[0], context, false, false)), context);
+    v.mkString(baseNameOf(*state.coerceToString(pos, *args[0], context, false, false)), context);
 }
 
 static RegisterPrimOp primop_baseNameOf({
@@ -1440,7 +1420,8 @@ static RegisterPrimOp primop_baseNameOf({
 static void prim_dirOf(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    Path dir = dirOf(state.coerceToString(pos, *args[0], context, false, false));
+    auto path = state.coerceToString(pos, *args[0], context, false, false);
+    auto dir = dirOf(*path);
     if (args[0]->type() == nPath) v.mkPath(dir); else v.mkString(dir, context);
 }
 
@@ -1458,19 +1439,19 @@ static RegisterPrimOp primop_dirOf({
 /* Return the contents of a file as a string. */
 static void prim_readFile(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    Path path;
-    try {
-        path = realisePath(state, pos, *args[0]);
-    } catch (InvalidPathError & e) {
-        throw EvalError({
-            .msg = hintfmt("cannot read '%1%', since path '%2%' is not valid", path, e.path),
-            .errPos = pos
-        });
-    }
-    string s = readFile(path);
-    if (s.find((char) 0) != string::npos)
+    auto path = realisePath(state, pos, *args[0]);
+    auto s = readFile(path);
+    if (s.find((char) 0) != std::string::npos)
         throw Error("the contents of the file '%1%' cannot be represented as a Nix string", path);
-    v.mkString(s);
+    StorePathSet refs;
+    if (state.store->isInStore(path)) {
+        try {
+            refs = state.store->queryPathInfo(state.store->toStorePath(path).first)->references;
+        } catch (Error &) { // FIXME: should be InvalidPathError
+        }
+    }
+    auto context = state.store->printStorePathSet(refs);
+    v.mkString(s, context);
 }
 
 static RegisterPrimOp primop_readFile({
@@ -1493,23 +1474,25 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
     for (auto v2 : args[0]->listItems()) {
         state.forceAttrs(*v2, pos);
 
-        string prefix;
-        Bindings::iterator i = v2->attrs->find(state.symbols.create("prefix"));
+        std::string prefix;
+        Bindings::iterator i = v2->attrs->find(state.sPrefix);
         if (i != v2->attrs->end())
             prefix = state.forceStringNoCtx(*i->value, pos);
 
         i = getAttr(
             state,
             "findFile",
-            "path",
+            state.sPath,
             v2->attrs,
             pos
         );
 
-        Path path;
+        PathSet context;
+        auto path = state.coerceToString(pos, *i->value, context, false, false).toOwned();
 
         try {
-            path = realisePath(state, pos, *i->value, { .requireAbsolutePath = false });
+            auto rewrites = state.realiseContext(context);
+            path = rewriteStrings(path, rewrites);
         } catch (InvalidPathError & e) {
             throw EvalError({
                 .msg = hintfmt("cannot find '%1%', since path '%2%' is not valid", path, e.path),
@@ -1517,10 +1500,11 @@ static void prim_findFile(EvalState & state, const Pos & pos, Value * * args, Va
             });
         }
 
+
         searchPath.emplace_back(prefix, path);
     }
 
-    string path = state.forceStringNoCtx(*args[1], pos);
+    auto path = state.forceStringNoCtx(*args[1], pos);
 
     v.mkPath(state.checkSourcePath(state.findFile(searchPath, path, pos)));
 }
@@ -1534,7 +1518,7 @@ static RegisterPrimOp primop_findFile(RegisterPrimOp::Info {
 /* Return the cryptographic hash of a file in base-16. */
 static void prim_hashFile(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string type = state.forceStringNoCtx(*args[0], pos);
+    auto type = state.forceStringNoCtx(*args[0], pos);
     std::optional<HashType> ht = parseHashType(type);
     if (!ht)
         throw Error({
@@ -1542,12 +1526,7 @@ static void prim_hashFile(EvalState & state, const Pos & pos, Value * * args, Va
             .errPos = pos
         });
 
-    Path path;
-    try {
-        path = realisePath(state, pos, *args[1]);
-    } catch (InvalidPathError & e) {
-        throw EvalError("cannot read '%s' since path '%s' is not valid, at %s", path, e.path, pos);
-    }
+    auto path = realisePath(state, pos, *args[1]);
 
     v.mkString(hashFile(*ht, path).to_string(Base16, false));
 }
@@ -1566,15 +1545,7 @@ static RegisterPrimOp primop_hashFile({
 /* Read a directory (without . or ..) */
 static void prim_readDir(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    Path path;
-    try {
-        path = realisePath(state, pos, *args[0]);
-    } catch (InvalidPathError & e) {
-        throw EvalError({
-            .msg = hintfmt("cannot read '%1%', since path '%2%' is not valid", path, e.path),
-            .errPos = pos
-        });
-    }
+    auto path = realisePath(state, pos, *args[0]);
 
     DirEntries entries = readDirectory(path);
 
@@ -1754,7 +1725,7 @@ static RegisterPrimOp primop_toJSON({
 /* Parse a JSON string to a value. */
 static void prim_fromJSON(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string s = state.forceStringNoCtx(*args[0], pos);
+    auto s = state.forceStringNoCtx(*args[0], pos);
     try {
         parseJSON(state, s, v);
     } catch (JSONParseError &e) {
@@ -1783,8 +1754,8 @@ static RegisterPrimOp primop_fromJSON({
 static void prim_toFile(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    string name = state.forceStringNoCtx(*args[0], pos);
-    string contents = state.forceString(*args[1], context, pos);
+    std::string name(state.forceStringNoCtx(*args[0], pos));
+    std::string contents(state.forceString(*args[1], context, pos));
 
     StorePathSet refs;
 
@@ -1892,7 +1863,7 @@ static RegisterPrimOp primop_toFile({
 static void addPath(
     EvalState & state,
     const Pos & pos,
-    const string & name,
+    const std::string & name,
     Path path,
     Value * filterFun,
     FileIngestionMethod method,
@@ -1909,10 +1880,13 @@ static void addPath(
         StorePathSet refs;
 
         if (state.store->isInStore(path)) {
+            try {
                 auto [storePath, subPath] = state.store->toStorePath(path);
                 // FIXME: we should scanForReferences on the path before adding it
                 refs = state.store->queryPathInfo(storePath)->references;
                 path = state.store->toRealPath(storePath) + subPath;
+            } catch (Error &) { // FIXME: should be InvalidPathError
+            }
         }
 
         path = evalSettings.pureEval && expectedHash
@@ -2042,14 +2016,14 @@ static void prim_path(EvalState & state, const Pos & pos, Value * * args, Value
 {
     state.forceAttrs(*args[0], pos);
     Path path;
-    string name;
+    std::string name;
     Value * filterFun = nullptr;
     auto method = FileIngestionMethod::Recursive;
     std::optional<Hash> expectedHash;
     PathSet context;
 
     for (auto & attr : *args[0]->attrs) {
-        const string & n(attr.name);
+        auto & n(attr.name);
         if (n == "path")
             path = state.coerceToPath(*attr.pos, *attr.value, context);
         else if (attr.name == state.sName)
@@ -2159,7 +2133,10 @@ static void prim_attrValues(EvalState & state, const Pos & pos, Value * * args,
         v.listElems()[n++] = (Value *) &i;
 
     std::sort(v.listElems(), v.listElems() + n,
-        [](Value * v1, Value * v2) { return (string) ((Attr *) v1)->name < (string) ((Attr *) v2)->name; });
+        [](Value * v1, Value * v2) {
+            std::string_view s1 = ((Attr *) v1)->name, s2 = ((Attr *) v2)->name;
+            return s1 < s2;
+        });
 
     for (unsigned int i = 0; i < n; ++i)
         v.listElems()[i] = ((Attr *) v.listElems()[i])->value;
@@ -2178,13 +2155,12 @@ static RegisterPrimOp primop_attrValues({
 /* Dynamic version of the `.' operator. */
 void prim_getAttr(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string attr = state.forceStringNoCtx(*args[0], pos);
+    auto attr = state.forceStringNoCtx(*args[0], pos);
     state.forceAttrs(*args[1], pos);
-    // !!! Should we create a symbol here or just do a lookup?
     Bindings::iterator i = getAttr(
         state,
         "getAttr",
-        attr,
+        state.symbols.create(attr),
         args[1]->attrs,
         pos
     );
@@ -2209,7 +2185,7 @@ static RegisterPrimOp primop_getAttr({
 /* Return position information of the specified attribute. */
 static void prim_unsafeGetAttrPos(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string attr = state.forceStringNoCtx(*args[0], pos);
+    auto attr = state.forceStringNoCtx(*args[0], pos);
     state.forceAttrs(*args[1], pos);
     Bindings::iterator i = args[1]->attrs->find(state.symbols.create(attr));
     if (i == args[1]->attrs->end())
@@ -2227,7 +2203,7 @@ static RegisterPrimOp primop_unsafeGetAttrPos(RegisterPrimOp::Info {
 /* Dynamic version of the `?' operator. */
 static void prim_hasAttr(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string attr = state.forceStringNoCtx(*args[0], pos);
+    auto attr = state.forceStringNoCtx(*args[0], pos);
     state.forceAttrs(*args[1], pos);
     v.mkBool(args[1]->attrs->find(state.symbols.create(attr)) != args[1]->attrs->end());
 }
@@ -2264,21 +2240,25 @@ static void prim_removeAttrs(EvalState & state, const Pos & pos, Value * * args,
     state.forceAttrs(*args[0], pos);
     state.forceList(*args[1], pos);
 
-    /* Get the attribute names to be removed. */
-    std::set<Symbol> names;
+    /* Get the attribute names to be removed.
+       We keep them as Attrs instead of Symbols so std::set_difference
+       can be used to remove them from attrs[0]. */
+    boost::container::small_vector<Attr, 64> names;
+    names.reserve(args[1]->listSize());
     for (auto elem : args[1]->listItems()) {
         state.forceStringNoCtx(*elem, pos);
-        names.insert(state.symbols.create(elem->string.s));
+        names.emplace_back(state.symbols.create(elem->string.s), nullptr);
     }
+    std::sort(names.begin(), names.end());
 
     /* Copy all attributes not in that set.  Note that we don't need
        to sort v.attrs because it's a subset of an already sorted
        vector. */
     auto attrs = state.buildBindings(args[0]->attrs->size());
-    for (auto & i : *args[0]->attrs) {
-        if (!names.count(i.name))
-            attrs.insert(i);
-    }
+    std::set_difference(
+        args[0]->attrs->begin(), args[0]->attrs->end(),
+        names.begin(), names.end(),
+        std::back_inserter(attrs));
     v.mkAttrs(attrs.alreadySorted());
 }
 
@@ -2301,7 +2281,7 @@ static RegisterPrimOp primop_removeAttrs({
 /* Builds a set from a list specifying (name, value) pairs.  To be
    precise, a list [{name = "name1"; value = value1;} ... {name =
    "nameN"; value = valueN;}] is transformed to {name1 = value1;
-   ... nameN = valueN;}.  In case of duplicate occurences of the same
+   ... nameN = valueN;}.  In case of duplicate occurrences of the same
    name, the first takes precedence. */
 static void prim_listToAttrs(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
@@ -2322,7 +2302,7 @@ static void prim_listToAttrs(EvalState & state, const Pos & pos, Value * * args,
             pos
         );
 
-        string name = state.forceStringNoCtx(*j->value, *j->pos);
+        auto name = state.forceStringNoCtx(*j->value, *j->pos);
 
         Symbol sym = state.symbols.create(name);
         if (seen.insert(sym).second) {
@@ -2522,7 +2502,7 @@ static void prim_zipAttrsWith(EvalState & state, const Pos & pos, Value * * args
     for (unsigned int n = 0; n < listSize; ++n) {
         Value * vElem = listElems[n];
         try {
-            state.forceAttrs(*vElem);
+            state.forceAttrs(*vElem, noPos);
             for (auto & attr : *vElem->attrs)
                 attrsSeen[attr.name].first++;
         } catch (TypeError & e) {
@@ -3054,7 +3034,7 @@ static void prim_groupBy(EvalState & state, const Pos & pos, Value * * args, Val
     for (auto vElem : args[1]->listItems()) {
         Value res;
         state.callFunction(*args[0], *vElem, res, pos);
-        string name = state.forceStringNoCtx(res, pos);
+        auto name = state.forceStringNoCtx(res, pos);
         Symbol sym = state.symbols.create(name);
         auto vector = attrs.try_emplace(sym, ValueVector()).first;
         vector->second.push_back(vElem);
@@ -3310,8 +3290,8 @@ static RegisterPrimOp primop_lessThan({
 static void prim_toString(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    string s = state.coerceToString(pos, *args[0], context, true, false);
-    v.mkString(s, context);
+    auto s = state.coerceToString(pos, *args[0], context, true, false);
+    v.mkString(*s, context);
 }
 
 static RegisterPrimOp primop_toString({
@@ -3347,7 +3327,7 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
     int start = state.forceInt(*args[0], pos);
     int len = state.forceInt(*args[1], pos);
     PathSet context;
-    string s = state.coerceToString(pos, *args[2], context);
+    auto s = state.coerceToString(pos, *args[2], context);
 
     if (start < 0)
         throw EvalError({
@@ -3355,7 +3335,7 @@ static void prim_substring(EvalState & state, const Pos & pos, Value * * args, V
             .errPos = pos
         });
 
-    v.mkString((unsigned int) start >= s.size() ? "" : string(s, start, len), context);
+    v.mkString((unsigned int) start >= s->size() ? "" : s->substr(start, len), context);
 }
 
 static RegisterPrimOp primop_substring({
@@ -3381,8 +3361,8 @@ static RegisterPrimOp primop_substring({
 static void prim_stringLength(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    string s = state.coerceToString(pos, *args[0], context);
-    v.mkInt(s.size());
+    auto s = state.coerceToString(pos, *args[0], context);
+    v.mkInt(s->size());
 }
 
 static RegisterPrimOp primop_stringLength({
@@ -3398,7 +3378,7 @@ static RegisterPrimOp primop_stringLength({
 /* Return the cryptographic hash of a string in base-16. */
 static void prim_hashString(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string type = state.forceStringNoCtx(*args[0], pos);
+    auto type = state.forceStringNoCtx(*args[0], pos);
     std::optional<HashType> ht = parseHashType(type);
     if (!ht)
         throw Error({
@@ -3407,7 +3387,7 @@ static void prim_hashString(EvalState & state, const Pos & pos, Value * * args,
         });
 
     PathSet context; // discarded
-    string s = state.forceString(*args[1], context, pos);
+    auto s = state.forceString(*args[1], context, pos);
 
     v.mkString(hashString(*ht, s).to_string(Base16, false));
 }
@@ -3425,7 +3405,18 @@ static RegisterPrimOp primop_hashString({
 
 struct RegexCache
 {
-    std::unordered_map<std::string, std::regex> cache;
+    // TODO use C++20 transparent comparison when available
+    std::unordered_map<std::string_view, std::regex> cache;
+    std::list<std::string> keys;
+
+    std::regex get(std::string_view re)
+    {
+        auto it = cache.find(re);
+        if (it != cache.end())
+            return it->second;
+        keys.emplace_back(re);
+        return cache.emplace(keys.back(), std::regex(keys.back(), std::regex::extended)).first->second;
+    }
 };
 
 std::shared_ptr<RegexCache> makeRegexCache()
@@ -3439,15 +3430,13 @@ void prim_match(EvalState & state, const Pos & pos, Value * * args, Value & v)
 
     try {
 
-        auto regex = state.regexCache->cache.find(re);
-        if (regex == state.regexCache->cache.end())
-            regex = state.regexCache->cache.emplace(re, std::regex(re, std::regex::extended)).first;
+        auto regex = state.regexCache->get(re);
 
         PathSet context;
-        const std::string str = state.forceString(*args[1], context, pos);
+        const auto str = state.forceString(*args[1], context, pos);
 
-        std::smatch match;
-        if (!std::regex_match(str, match, regex->second)) {
+        std::cmatch match;
+        if (!std::regex_match(str.begin(), str.end(), match, regex)) {
             v.mkNull();
             return;
         }
@@ -3516,19 +3505,19 @@ static RegisterPrimOp primop_match({
 
 /* Split a string with a regular expression, and return a list of the
    non-matching parts interleaved by the lists of the matching groups. */
-static void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v)
+void prim_split(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     auto re = state.forceStringNoCtx(*args[0], pos);
 
     try {
 
-        std::regex regex(re, std::regex::extended);
+        auto regex = state.regexCache->get(re);
 
         PathSet context;
-        const std::string str = state.forceString(*args[1], context, pos);
+        const auto str = state.forceString(*args[1], context, pos);
 
-        auto begin = std::sregex_iterator(str.begin(), str.end(), regex);
-        auto end = std::sregex_iterator();
+        auto begin = std::cregex_iterator(str.begin(), str.end(), regex);
+        auto end = std::cregex_iterator();
 
         // Any matches results are surrounded by non-matching results.
         const size_t len = std::distance(begin, end);
@@ -3540,9 +3529,9 @@ static void prim_split(EvalState & state, const Pos & pos, Value * * args, Value
             return;
         }
 
-        for (std::sregex_iterator i = begin; i != end; ++i) {
+        for (auto i = begin; i != end; ++i) {
             assert(idx <= 2 * len + 1 - 3);
-            std::smatch match = *i;
+            auto match = *i;
 
             // Add a string for non-matched characters.
             (v.listElems()[idx++] = state.allocValue())->mkString(match.prefix().str());
@@ -3627,13 +3616,13 @@ static void prim_concatStringsSep(EvalState & state, const Pos & pos, Value * *
     auto sep = state.forceString(*args[0], context, pos);
     state.forceList(*args[1], pos);
 
-    string res;
+    std::string res;
     res.reserve((args[1]->listSize() + 32) * sep.size());
     bool first = true;
 
     for (auto elem : args[1]->listItems()) {
         if (first) first = false; else res += sep;
-        res += state.coerceToString(pos, *elem, context);
+        res += *state.coerceToString(pos, *elem, context);
     }
 
     v.mkString(res, context);
@@ -3660,23 +3649,23 @@ static void prim_replaceStrings(EvalState & state, const Pos & pos, Value * * ar
             .errPos = pos
         });
 
-    vector<string> from;
+    std::vector<std::string> from;
     from.reserve(args[0]->listSize());
     for (auto elem : args[0]->listItems())
-        from.push_back(state.forceString(*elem, pos));
+        from.emplace_back(state.forceString(*elem, pos));
 
-    vector<std::pair<string, PathSet>> to;
+    std::vector<std::pair<std::string, PathSet>> to;
     to.reserve(args[1]->listSize());
     for (auto elem : args[1]->listItems()) {
         PathSet ctx;
         auto s = state.forceString(*elem, ctx, pos);
-        to.push_back(std::make_pair(std::move(s), std::move(ctx)));
+        to.emplace_back(s, std::move(ctx));
     }
 
     PathSet context;
     auto s = state.forceString(*args[2], context, pos);
 
-    string res;
+    std::string res;
     // Loops one past last character to handle the case where 'from' contains an empty string.
     for (size_t p = 0; p <= s.size(); ) {
         bool found = false;
@@ -3732,7 +3721,7 @@ static RegisterPrimOp primop_replaceStrings({
 
 static void prim_parseDrvName(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string name = state.forceStringNoCtx(*args[0], pos);
+    auto name = state.forceStringNoCtx(*args[0], pos);
     DrvName parsed(name);
     auto attrs = state.buildBindings(2);
     attrs.alloc(state.sName).mkString(parsed.name);
@@ -3756,8 +3745,8 @@ static RegisterPrimOp primop_parseDrvName({
 
 static void prim_compareVersions(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string version1 = state.forceStringNoCtx(*args[0], pos);
-    string version2 = state.forceStringNoCtx(*args[1], pos);
+    auto version1 = state.forceStringNoCtx(*args[0], pos);
+    auto version2 = state.forceStringNoCtx(*args[1], pos);
     v.mkInt(compareVersions(version1, version2));
 }
 
@@ -3776,14 +3765,14 @@ static RegisterPrimOp primop_compareVersions({
 
 static void prim_splitVersion(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
-    string version = state.forceStringNoCtx(*args[0], pos);
+    auto version = state.forceStringNoCtx(*args[0], pos);
     auto iter = version.cbegin();
     Strings components;
     while (iter != version.cend()) {
         auto component = nextComponent(iter, version.cend());
         if (component.empty())
             break;
-        components.emplace_back(std::move(component));
+        components.emplace_back(component);
     }
     state.mkList(v, components.size());
     for (const auto & [n, component] : enumerate(components))
@@ -3911,9 +3900,12 @@ void EvalState::createBaseEnv()
 
     /* Note: we have to initialize the 'derivation' constant *after*
        building baseEnv/staticBaseEnv because it uses 'builtins'. */
-    eval(parse(
+    char code[] =
         #include "primops/derivation.nix.gen.hh"
-        , foFile, sDerivationNix, "/", staticBaseEnv), *vDerivation);
+        // the parser needs two NUL bytes as terminators; one of them
+        // is implied by being a C string.
+        "\0";
+    eval(parse(code, sizeof(code), foFile, sDerivationNix, "/", staticBaseEnv), *vDerivation);
 }
 
 

src/libexpr/primops/context.cc

@@ -7,7 +7,8 @@ namespace nix {
 static void prim_unsafeDiscardStringContext(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    v.mkString(state.coerceToString(pos, *args[0], context));
+    auto s = state.coerceToString(pos, *args[0], context);
+    v.mkString(*s);
 }
 
 static RegisterPrimOp primop_unsafeDiscardStringContext("__unsafeDiscardStringContext", 1, prim_unsafeDiscardStringContext);
@@ -32,13 +33,13 @@ static RegisterPrimOp primop_hasContext("__hasContext", 1, prim_hasContext);
 static void prim_unsafeDiscardOutputDependency(EvalState & state, const Pos & pos, Value * * args, Value & v)
 {
     PathSet context;
-    string s = state.coerceToString(pos, *args[0], context);
+    auto s = state.coerceToString(pos, *args[0], context);
 
     PathSet context2;
     for (auto & p : context)
-        context2.insert(p.at(0) == '=' ? string(p, 1) : p);
+        context2.insert(p.at(0) == '=' ? std::string(p, 1) : p);
 
-    v.mkString(s, context2);
+    v.mkString(*s, context2);
 }
 
 static RegisterPrimOp primop_unsafeDiscardOutputDependency("__unsafeDiscardOutputDependency", 1, prim_unsafeDiscardOutputDependency);
@@ -75,13 +76,13 @@ static void prim_getContext(EvalState & state, const Pos & pos, Value * * args,
     auto contextInfos = std::map<Path, ContextInfo>();
     for (const auto & p : context) {
         Path drv;
-        string output;
+        std::string output;
         const Path * path = &p;
         if (p.at(0) == '=') {
-            drv = string(p, 1);
+            drv = std::string(p, 1);
             path = &drv;
         } else if (p.at(0) == '!') {
-            std::pair<string, string> ctx = decodeContext(p);
+            std::pair<std::string, std::string> ctx = decodeContext(p);
             drv = ctx.first;
             output = ctx.second;
             path = &drv;
@@ -165,7 +166,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
                         .errPos = *i.pos
                     });
                 }
-                context.insert("=" + string(i.name));
+                context.insert("=" + std::string(i.name));
             }
         }
 
@@ -180,7 +181,7 @@ static void prim_appendContext(EvalState & state, const Pos & pos, Value * * arg
             }
             for (auto elem : iter->value->listItems()) {
                 auto name = state.forceStringNoCtx(*elem, *iter->pos);
-                context.insert("!" + name + "!" + string(i.name));
+                context.insert(concatStrings("!", name, "!", i.name));
             }
         }
     }

src/libexpr/primops/fetchMercurial.cc

@@ -12,7 +12,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
     std::string url;
     std::optional<Hash> rev;
     std::optional<std::string> ref;
-    std::string name = "source";
+    std::string_view name = "source";
     PathSet context;
 
     state.forceValue(*args[0], pos);
@@ -22,14 +22,14 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
         state.forceAttrs(*args[0], pos);
 
         for (auto & attr : *args[0]->attrs) {
-            string n(attr.name);
+            std::string_view n(attr.name);
             if (n == "url")
-                url = state.coerceToString(*attr.pos, *attr.value, context, false, false);
+                url = state.coerceToString(*attr.pos, *attr.value, context, false, false).toOwned();
             else if (n == "rev") {
                 // Ugly: unlike fetchGit, here the "rev" attribute can
                 // be both a revision or a branch/tag name.
                 auto value = state.forceStringNoCtx(*attr.value, *attr.pos);
-                if (std::regex_match(value, revRegex))
+                if (std::regex_match(value.begin(), value.end(), revRegex))
                     rev = Hash::parseAny(value, htSHA1);
                 else
                     ref = value;
@@ -50,7 +50,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
             });
 
     } else
-        url = state.coerceToString(pos, *args[0], context, false, false);
+        url = state.coerceToString(pos, *args[0], context, false, false).toOwned();
 
     // FIXME: git externals probably can be used to bypass the URI
     // whitelist. Ah well.
@@ -62,7 +62,7 @@ static void prim_fetchMercurial(EvalState & state, const Pos & pos, Value * * ar
     fetchers::Attrs attrs;
     attrs.insert_or_assign("type", "hg");
     attrs.insert_or_assign("url", url.find("://") != std::string::npos ? url : "file://" + url);
-    attrs.insert_or_assign("name", name);
+    attrs.insert_or_assign("name", std::string(name));
     if (ref) attrs.insert_or_assign("ref", *ref);
     if (rev) attrs.insert_or_assign("rev", rev->gitRev());
     auto input = fetchers::Input::fromAttrs(std::move(attrs));

src/libexpr/primops/fetchTree.cc

@@ -19,7 +19,7 @@ void emitTreeAttrs(
     bool emptyRevFallback,
     bool forceDirty)
 {
-    assert(input.isImmutable());
+    assert(input.isLocked());
 
     auto attrs = state.buildBindings(8);
 
@@ -125,7 +125,7 @@ static void fetchTree(
             if (attr.name == state.sType) continue;
             state.forceValue(*attr.value, *attr.pos);
             if (attr.value->type() == nPath || attr.value->type() == nString) {
-                auto s = state.coerceToString(*attr.pos, *attr.value, context, false, false);
+                auto s = state.coerceToString(*attr.pos, *attr.value, context, false, false).toOwned();
                 attrs.emplace(attr.name,
                     attr.name == "url"
                     ? type == "git"
@@ -151,7 +151,7 @@ static void fetchTree(
 
         input = fetchers::Input::fromAttrs(std::move(attrs));
     } else {
-        auto url = state.coerceToString(pos, *args[0], context, false, false);
+        auto url = state.coerceToString(pos, *args[0], context, false, false).toOwned();
 
         if (type == "git") {
             fetchers::Attrs attrs;
@@ -166,8 +166,8 @@ static void fetchTree(
     if (!evalSettings.pureEval && !input.isDirect())
         input = lookupInRegistries(state.store, input).first;
 
-    if (evalSettings.pureEval && !input.isImmutable())
-        throw Error("in pure evaluation mode, 'fetchTree' requires an immutable input, at %s", pos);
+    if (evalSettings.pureEval && !input.isLocked())
+        throw Error("in pure evaluation mode, 'fetchTree' requires a locked input, at %s", pos);
 
     auto [tree, input2] = input.fetch(state.store);
 
@@ -186,7 +186,7 @@ static void prim_fetchTree(EvalState & state, const Pos & pos, Value * * args, V
 static RegisterPrimOp primop_fetchTree("fetchTree", 1, prim_fetchTree);
 
 static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
-    const string & who, bool unpack, std::string name)
+    const std::string & who, bool unpack, std::string name)
 {
     std::optional<std::string> url;
     std::optional<Hash> expectedHash;
@@ -198,7 +198,7 @@ static void fetch(EvalState & state, const Pos & pos, Value * * args, Value & v,
         state.forceAttrs(*args[0], pos);
 
         for (auto & attr : *args[0]->attrs) {
-            string n(attr.name);
+            std::string n(attr.name);
             if (n == "url")
                 url = state.forceStringNoCtx(*attr.value, *attr.pos);
             else if (n == "sha256")

src/libexpr/primops/fromTOML.cc

@@ -9,7 +9,7 @@ static void prim_fromTOML(EvalState & state, const Pos & pos, Value * * args, Va
 {
     auto toml = state.forceStringNoCtx(*args[0], pos);
 
-    std::istringstream tomlStream(toml);
+    std::istringstream tomlStream(std::string{toml});
 
     std::function<void(Value &, toml::value)> visit;
 

src/libexpr/symbol-table.hh

@@ -1,7 +1,8 @@
 #pragma once
 
+#include <list>
 #include <map>
-#include <unordered_set>
+#include <unordered_map>
 
 #include "types.hh"
 
@@ -16,8 +17,8 @@ namespace nix {
 class Symbol
 {
 private:
-    const string * s; // pointer into SymbolTable
-    Symbol(const string * s) : s(s) { };
+    const std::string * s; // pointer into SymbolTable
+    Symbol(const std::string * s) : s(s) { };
     friend class SymbolTable;
 
 public:
@@ -70,15 +71,21 @@ public:
 class SymbolTable
 {
 private:
-    typedef std::unordered_set<string> Symbols;
-    Symbols symbols;
+    std::unordered_map<std::string_view, Symbol> symbols;
+    std::list<std::string> store;
 
 public:
     Symbol create(std::string_view s)
     {
-        // FIXME: avoid allocation if 's' already exists in the symbol table.
-        std::pair<Symbols::iterator, bool> res = symbols.emplace(std::string(s));
-        return Symbol(&*res.first);
+        // Most symbols are looked up more than once, so we trade off insertion performance
+        // for lookup performance.
+        // TODO: could probably be done more efficiently with transparent Hash and Equals
+        // on the original implementation using unordered_set
+        auto it = symbols.find(s);
+        if (it != symbols.end()) return it->second;
+
+        auto & rawSym = store.emplace_back(s);
+        return symbols.emplace(rawSym, Symbol(&rawSym)).first->second;
     }
 
     size_t size() const
@@ -91,7 +98,7 @@ public:
     template<typename T>
     void dump(T callback)
     {
-        for (auto & s : symbols)
+        for (auto & s : store)
             callback(s);
     }
 };

src/libexpr/value-to-xml.cc

@@ -9,7 +9,7 @@
 namespace nix {
 
 
-static XMLAttrs singletonAttrs(const string & name, const string & value)
+static XMLAttrs singletonAttrs(const std::string & name, const std::string & value)
 {
     XMLAttrs attrs;
     attrs[name] = value;
@@ -142,7 +142,7 @@ static void printValueAsXML(EvalState & state, bool strict, bool location,
                 if (!v.lambda.fun->arg.empty()) attrs["name"] = v.lambda.fun->arg;
                 if (v.lambda.fun->formals->ellipsis) attrs["ellipsis"] = "1";
                 XMLOpenElement _(doc, "attrspat", attrs);
-                for (auto & i : v.lambda.fun->formals->formals)
+                for (auto & i : v.lambda.fun->formals->lexicographicOrder())
                     doc.writeEmptyElement("attr", singletonAttrs("name", i.name));
             } else
                 doc.writeEmptyElement("varpat", singletonAttrs("name", v.lambda.fun->arg));

src/libexpr/value.hh

@@ -77,15 +77,15 @@ class ExternalValueBase
 
     public:
     /* Return a simple string describing the type */
-    virtual string showType() const = 0;
+    virtual std::string showType() const = 0;
 
     /* Return a string to be used in builtins.typeOf */
-    virtual string typeOf() const = 0;
+    virtual std::string typeOf() const = 0;
 
     /* Coerce the value to a string. Defaults to uncoercable, i.e. throws an
-     * error
+     * error.
      */
-    virtual string coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const;
+    virtual std::string coerceToString(const Pos & pos, PathSet & context, bool copyMore, bool copyToStore) const;
 
     /* Compare to another value of the same type. Defaults to uncomparable,
      * i.e. always false.
@@ -241,6 +241,8 @@ public:
 
     void mkString(std::string_view s, const PathSet & context);
 
+    void mkStringMove(const char * s, const PathSet & context);
+
     inline void mkString(const Symbol & s)
     {
         mkString(((const std::string &) s).c_str());

src/libfetchers/cache.cc

@@ -52,13 +52,13 @@ struct CacheImpl : Cache
         const Attrs & inAttrs,
         const Attrs & infoAttrs,
         const StorePath & storePath,
-        bool immutable) override
+        bool locked) override
     {
         _state.lock()->add.use()
             (attrsToJSON(inAttrs).dump())
             (attrsToJSON(infoAttrs).dump())
             (store->printStorePath(storePath))
-            (immutable)
+            (locked)
             (time(0)).exec();
     }
 
@@ -91,7 +91,7 @@ struct CacheImpl : Cache
 
         auto infoJSON = stmt.getStr(0);
         auto storePath = store->parseStorePath(stmt.getStr(1));
-        auto immutable = stmt.getInt(2) != 0;
+        auto locked = stmt.getInt(2) != 0;
         auto timestamp = stmt.getInt(3);
 
         store->addTempRoot(storePath);
@@ -105,7 +105,7 @@ struct CacheImpl : Cache
             inAttrsJSON, infoJSON, store->printStorePath(storePath));
 
         return Result {
-            .expired = !immutable && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
+            .expired = !locked && (settings.tarballTtl.get() == 0 || timestamp + settings.tarballTtl < time(0)),
             .infoAttrs = jsonToAttrs(nlohmann::json::parse(infoJSON)),
             .storePath = std::move(storePath)
         };

src/libfetchers/cache.hh

@@ -13,7 +13,7 @@ struct Cache
         const Attrs & inAttrs,
         const Attrs & infoAttrs,
         const StorePath & storePath,
-        bool immutable) = 0;
+        bool locked) = 0;
 
     virtual std::optional<std::pair<Attrs, StorePath>> lookup(
         ref<Store> store,

src/libfetchers/fetchers.cc

@@ -24,11 +24,11 @@ static void fixupInput(Input & input)
     input.getType();
     input.getRef();
     if (input.getRev())
-        input.immutable = true;
+        input.locked = true;
     input.getRevCount();
     input.getLastModified();
     if (input.getNarHash())
-        input.immutable = true;
+        input.locked = true;
 }
 
 Input Input::fromURL(const ParsedURL & url)
@@ -124,15 +124,13 @@ std::pair<Tree, Input> Input::fetch(ref<Store> store) const
             debug("using substituted/cached input '%s' in '%s'",
                 to_string(), store->printStorePath(storePath));
 
-            auto actualPath = store->toRealPath(storePath);
-
-            return {fetchers::Tree(std::move(actualPath), std::move(storePath)), *this};
+            return {Tree { .actualPath = store->toRealPath(storePath), .storePath = std::move(storePath) }, *this};
         } catch (Error & e) {
             debug("substitution of input '%s' failed: %s", to_string(), e.what());
         }
     }
 
-    auto [tree, input] = [&]() -> std::pair<Tree, Input> {
+    auto [storePath, input] = [&]() -> std::pair<StorePath, Input> {
         try {
             return scheme->fetch(store, *this);
         } catch (Error & e) {
@@ -141,8 +139,10 @@ std::pair<Tree, Input> Input::fetch(ref<Store> store) const
         }
     }();
 
-    if (tree.actualPath == "")
-        tree.actualPath = store->toRealPath(tree.storePath);
+    Tree tree {
+        .actualPath = store->toRealPath(storePath),
+        .storePath = storePath,
+    };
 
     auto narHash = store->queryPathInfo(tree.storePath)->narHash;
     input.attrs.insert_or_assign("narHash", narHash.to_string(SRI, true));
@@ -165,7 +165,7 @@ std::pair<Tree, Input> Input::fetch(ref<Store> store) const
                 input.to_string(), *prevRevCount);
     }
 
-    input.immutable = true;
+    input.locked = true;
 
     assert(input.hasAllInfo());
 
@@ -209,7 +209,7 @@ StorePath Input::computeStorePath(Store & store) const
 {
     auto narHash = getNarHash();
     if (!narHash)
-        throw Error("cannot compute store path for mutable input '%s'", to_string());
+        throw Error("cannot compute store path for unlocked input '%s'", to_string());
     return store.makeFixedOutputPath(FileIngestionMethod::Recursive, *narHash, getName());
 }
 

src/libfetchers/fetchers.hh

@@ -16,7 +16,6 @@ struct Tree
 {
     Path actualPath;
     StorePath storePath;
-    Tree(Path && actualPath, StorePath && storePath) : actualPath(actualPath), storePath(std::move(storePath)) {}
 };
 
 struct InputScheme;
@@ -35,7 +34,7 @@ struct Input
 
     std::shared_ptr<InputScheme> scheme; // note: can be null
     Attrs attrs;
-    bool immutable = false;
+    bool locked = false;
     bool direct = true;
 
     /* path of the parent of this input, used for relative path resolution */
@@ -60,9 +59,9 @@ public:
        one that goes through a registry. */
     bool isDirect() const { return direct; }
 
-    /* Check whether this is an "immutable" input, that is,
+    /* Check whether this is a "locked" input, that is,
        one that contains a commit hash or content hash. */
-    bool isImmutable() const { return immutable; }
+    bool isLocked() const { return locked; }
 
     bool hasAllInfo() const;
 
@@ -70,6 +69,8 @@ public:
 
     bool contains(const Input & other) const;
 
+    /* Fetch the input into the Nix store, returning the location in
+       the Nix store and the locked input. */
     std::pair<Tree, Input> fetch(ref<Store> store) const;
 
     Input applyOverrides(
@@ -131,7 +132,7 @@ struct InputScheme
 
     virtual void markChangedFile(const Input & input, std::string_view file, std::optional<std::string> commitMsg);
 
-    virtual std::pair<Tree, Input> fetch(ref<Store> store, const Input & input) = 0;
+    virtual std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) = 0;
 };
 
 void registerInputScheme(std::shared_ptr<InputScheme> && fetcher);
@@ -147,14 +148,14 @@ DownloadFileResult downloadFile(
     ref<Store> store,
     const std::string & url,
     const std::string & name,
-    bool immutable,
+    bool locked,
     const Headers & headers = {});
 
 std::pair<Tree, time_t> downloadTarball(
     ref<Store> store,
     const std::string & url,
     const std::string & name,
-    bool immutable,
+    bool locked,
     const Headers & headers = {});
 
 }

src/libfetchers/git.cc

@@ -172,7 +172,7 @@ struct GitInputScheme : InputScheme
         return {isLocal, isLocal ? url.path : url.base};
     }
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & _input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
     {
         Input input(_input);
 
@@ -187,7 +187,7 @@ struct GitInputScheme : InputScheme
         if (submodules) cacheType += "-submodules";
         if (allRefs) cacheType += "-all-refs";
 
-        auto getImmutableAttrs = [&]()
+        auto getLockedAttrs = [&]()
         {
             return Attrs({
                 {"type", cacheType},
@@ -197,21 +197,18 @@ struct GitInputScheme : InputScheme
         };
 
         auto makeResult = [&](const Attrs & infoAttrs, StorePath && storePath)
-            -> std::pair<Tree, Input>
+            -> std::pair<StorePath, Input>
         {
             assert(input.getRev());
             assert(!_input.getRev() || _input.getRev() == input.getRev());
             if (!shallow)
                 input.attrs.insert_or_assign("revCount", getIntAttr(infoAttrs, "revCount"));
             input.attrs.insert_or_assign("lastModified", getIntAttr(infoAttrs, "lastModified"));
-            return {
-                Tree(store->toRealPath(storePath), std::move(storePath)),
-                input
-            };
+            return {std::move(storePath), input};
         };
 
         if (input.getRev()) {
-            if (auto res = getCache()->lookup(store, getImmutableAttrs()))
+            if (auto res = getCache()->lookup(store, getLockedAttrs()))
                 return makeResult(res->first, std::move(res->second));
         }
 
@@ -285,16 +282,13 @@ struct GitInputScheme : InputScheme
                     "lastModified",
                     haveCommits ? std::stoull(runProgram("git", true, { "-C", actualUrl, "log", "-1", "--format=%ct", "--no-show-signature", "HEAD" })) : 0);
 
-                return {
-                    Tree(store->toRealPath(storePath), std::move(storePath)),
-                    input
-                };
+                return {std::move(storePath), input};
             }
         }
 
         if (!input.getRef()) input.attrs.insert_or_assign("ref", isLocal ? readHead(actualUrl) : "master");
 
-        Attrs mutableAttrs({
+        Attrs unlockedAttrs({
             {"type", cacheType},
             {"name", name},
             {"url", actualUrl},
@@ -313,7 +307,7 @@ struct GitInputScheme : InputScheme
 
         } else {
 
-            if (auto res = getCache()->lookup(store, mutableAttrs)) {
+            if (auto res = getCache()->lookup(store, unlockedAttrs)) {
                 auto rev2 = Hash::parseAny(getStrAttr(res->first, "rev"), htSHA1);
                 if (!input.getRev() || input.getRev() == rev2) {
                     input.attrs.insert_or_assign("rev", rev2.gitRev());
@@ -410,7 +404,7 @@ struct GitInputScheme : InputScheme
 
         /* Now that we know the ref, check again whether we have it in
            the store. */
-        if (auto res = getCache()->lookup(store, getImmutableAttrs()))
+        if (auto res = getCache()->lookup(store, getLockedAttrs()))
             return makeResult(res->first, std::move(res->second));
 
         Path tmpDir = createTempDir();
@@ -482,14 +476,14 @@ struct GitInputScheme : InputScheme
         if (!_input.getRev())
             getCache()->add(
                 store,
-                mutableAttrs,
+                unlockedAttrs,
                 infoAttrs,
                 storePath,
                 false);
 
         getCache()->add(
             store,
-            getImmutableAttrs(),
+            getLockedAttrs(),
             infoAttrs,
             storePath,
             true);

src/libfetchers/github.cc

@@ -8,6 +8,7 @@
 
 #include <optional>
 #include <nlohmann/json.hpp>
+#include <fstream>
 
 namespace nix::fetchers {
 
@@ -17,7 +18,7 @@ struct DownloadUrl
     Headers headers;
 };
 
-// A github or gitlab host
+// A github, gitlab, or sourcehut host
 const static std::string hostRegexS = "[a-zA-Z0-9.]*"; // FIXME: check
 std::regex hostRegex(hostRegexS, std::regex::ECMAScript);
 
@@ -180,7 +181,7 @@ struct GitArchiveInputScheme : InputScheme
 
     virtual DownloadUrl getDownloadUrl(const Input & input) const = 0;
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & _input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
     {
         Input input(_input);
 
@@ -192,17 +193,14 @@ struct GitArchiveInputScheme : InputScheme
         input.attrs.erase("ref");
         input.attrs.insert_or_assign("rev", rev->gitRev());
 
-        Attrs immutableAttrs({
+        Attrs lockedAttrs({
             {"type", "git-tarball"},
             {"rev", rev->gitRev()},
         });
 
-        if (auto res = getCache()->lookup(store, immutableAttrs)) {
+        if (auto res = getCache()->lookup(store, lockedAttrs)) {
             input.attrs.insert_or_assign("lastModified", getIntAttr(res->first, "lastModified"));
-            return {
-                Tree(store->toRealPath(res->second), std::move(res->second)),
-                input
-            };
+            return {std::move(res->second), input};
         }
 
         auto url = getDownloadUrl(input);
@@ -213,7 +211,7 @@ struct GitArchiveInputScheme : InputScheme
 
         getCache()->add(
             store,
-            immutableAttrs,
+            lockedAttrs,
             {
                 {"rev", rev->gitRev()},
                 {"lastModified", uint64_t(lastModified)}
@@ -221,7 +219,7 @@ struct GitArchiveInputScheme : InputScheme
             tree.storePath,
             true);
 
-        return {std::move(tree), input};
+        return {std::move(tree.storePath), input};
     }
 };
 
@@ -348,7 +346,95 @@ struct GitLabInputScheme : GitArchiveInputScheme
     }
 };
 
+struct SourceHutInputScheme : GitArchiveInputScheme
+{
+    std::string type() override { return "sourcehut"; }
+
+    std::optional<std::pair<std::string, std::string>> accessHeaderFromToken(const std::string & token) const override
+    {
+        // SourceHut supports both PAT and OAuth2. See
+        // https://man.sr.ht/meta.sr.ht/oauth.md
+        return std::pair<std::string, std::string>("Authorization", fmt("Bearer %s", token));
+        // Note: This currently serves no purpose, as this kind of authorization
+        // does not allow for downloading tarballs on sourcehut private repos.
+        // Once it is implemented, however, should work as expected.
+    }
+
+    Hash getRevFromRef(nix::ref<Store> store, const Input & input) const override
+    {
+        // TODO: In the future, when the sourcehut graphql API is implemented for mercurial
+        // and with anonymous access, this method should use it instead.
+
+        auto ref = *input.getRef();
+
+        auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
+        auto base_url = fmt("https://%s/%s/%s",
+            host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"));
+
+        Headers headers = makeHeadersWithAuthTokens(host);
+
+        std::string ref_uri;
+        if (ref == "HEAD") {
+            auto file = store->toRealPath(
+                downloadFile(store, fmt("%s/HEAD", base_url), "source", false, headers).storePath);
+            std::ifstream is(file);
+            std::string line;
+            getline(is, line);
+
+            auto ref_index = line.find("ref: ");
+            if (ref_index == std::string::npos) {
+                throw BadURL("in '%d', couldn't resolve HEAD ref '%d'", input.to_string(), ref);
+            }
+
+            ref_uri = line.substr(ref_index+5, line.length()-1);
+        } else
+            ref_uri = fmt("refs/heads/%s", ref);
+
+        auto file = store->toRealPath(
+            downloadFile(store, fmt("%s/info/refs", base_url), "source", false, headers).storePath);
+        std::ifstream is(file);
+
+        std::string line;
+        std::string id;
+        while(getline(is, line)) {
+            auto index = line.find(ref_uri);
+            if (index != std::string::npos) {
+                id = line.substr(0, index-1);
+                break;
+            }
+        }
+
+        if(id.empty())
+            throw BadURL("in '%d', couldn't find ref '%d'", input.to_string(), ref);
+
+        auto rev = Hash::parseAny(id, htSHA1);
+        debug("HEAD revision for '%s' is %s", fmt("%s/%s", base_url, ref), rev.gitRev());
+        return rev;
+    }
+
+    DownloadUrl getDownloadUrl(const Input & input) const override
+    {
+        auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
+        auto url = fmt("https://%s/%s/%s/archive/%s.tar.gz",
+            host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo"),
+            input.getRev()->to_string(Base16, false));
+
+        Headers headers = makeHeadersWithAuthTokens(host);
+        return DownloadUrl { url, headers };
+    }
+
+    void clone(const Input & input, const Path & destDir) override
+    {
+        auto host = maybeGetStrAttr(input.attrs, "host").value_or("git.sr.ht");
+        Input::fromURL(fmt("git+https://%s/%s/%s",
+                host, getStrAttr(input.attrs, "owner"), getStrAttr(input.attrs, "repo")))
+            .applyOverrides(input.getRef(), input.getRev())
+            .clone(destDir);
+    }
+};
+
 static auto rGitHubInputScheme = OnStartup([] { registerInputScheme(std::make_unique<GitHubInputScheme>()); });
 static auto rGitLabInputScheme = OnStartup([] { registerInputScheme(std::make_unique<GitLabInputScheme>()); });
+static auto rSourceHutInputScheme = OnStartup([] { registerInputScheme(std::make_unique<SourceHutInputScheme>()); });
 
 }

src/libfetchers/indirect.cc

@@ -94,7 +94,7 @@ struct IndirectInputScheme : InputScheme
         return input;
     }
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
     {
         throw Error("indirect input '%s' cannot be fetched directly", input.to_string());
     }

src/libfetchers/mercurial.cc

@@ -26,7 +26,7 @@ static RunOptions hgOptions(const Strings & args)
 }
 
 // runProgram wrapper that uses hgOptions instead of stock RunOptions.
-static string runHg(const Strings & args, const std::optional<std::string> & input = {})
+static std::string runHg(const Strings & args, const std::optional<std::string> & input = {})
 {
     RunOptions opts = hgOptions(args);
     opts.input = input;
@@ -143,7 +143,7 @@ struct MercurialInputScheme : InputScheme
         return {isLocal, isLocal ? url.path : url.base};
     }
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & _input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & _input) override
     {
         Input input(_input);
 
@@ -193,16 +193,13 @@ struct MercurialInputScheme : InputScheme
 
                 auto storePath = store->addToStore(input.getName(), actualUrl, FileIngestionMethod::Recursive, htSHA256, filter);
 
-                return {
-                    Tree(store->toRealPath(storePath), std::move(storePath)),
-                    input
-                };
+                return {std::move(storePath), input};
             }
         }
 
         if (!input.getRef()) input.attrs.insert_or_assign("ref", "default");
 
-        auto getImmutableAttrs = [&]()
+        auto getLockedAttrs = [&]()
         {
             return Attrs({
                 {"type", "hg"},
@@ -212,32 +209,29 @@ struct MercurialInputScheme : InputScheme
         };
 
         auto makeResult = [&](const Attrs & infoAttrs, StorePath && storePath)
-            -> std::pair<Tree, Input>
+            -> std::pair<StorePath, Input>
         {
             assert(input.getRev());
             assert(!_input.getRev() || _input.getRev() == input.getRev());
             input.attrs.insert_or_assign("revCount", getIntAttr(infoAttrs, "revCount"));
-            return {
-                Tree(store->toRealPath(storePath), std::move(storePath)),
-                input
-            };
+            return {std::move(storePath), input};
         };
 
         if (input.getRev()) {
-            if (auto res = getCache()->lookup(store, getImmutableAttrs()))
+            if (auto res = getCache()->lookup(store, getLockedAttrs()))
                 return makeResult(res->first, std::move(res->second));
         }
 
         auto revOrRef = input.getRev() ? input.getRev()->gitRev() : *input.getRef();
 
-        Attrs mutableAttrs({
+        Attrs unlockedAttrs({
             {"type", "hg"},
             {"name", name},
             {"url", actualUrl},
             {"ref", *input.getRef()},
         });
 
-        if (auto res = getCache()->lookup(store, mutableAttrs)) {
+        if (auto res = getCache()->lookup(store, unlockedAttrs)) {
             auto rev2 = Hash::parseAny(getStrAttr(res->first, "rev"), htSHA1);
             if (!input.getRev() || input.getRev() == rev2) {
                 input.attrs.insert_or_assign("rev", rev2.gitRev());
@@ -260,7 +254,7 @@ struct MercurialInputScheme : InputScheme
                     runHg({ "pull", "-R", cacheDir, "--", actualUrl });
                 }
                 catch (ExecError & e) {
-                    string transJournal = cacheDir + "/.hg/store/journal";
+                    auto transJournal = cacheDir + "/.hg/store/journal";
                     /* hg throws "abandoned transaction" error only if this file exists */
                     if (pathExists(transJournal)) {
                         runHg({ "recover", "-R", cacheDir });
@@ -283,7 +277,7 @@ struct MercurialInputScheme : InputScheme
         auto revCount = std::stoull(tokens[1]);
         input.attrs.insert_or_assign("ref", tokens[2]);
 
-        if (auto res = getCache()->lookup(store, getImmutableAttrs()))
+        if (auto res = getCache()->lookup(store, getLockedAttrs()))
             return makeResult(res->first, std::move(res->second));
 
         Path tmpDir = createTempDir();
@@ -303,14 +297,14 @@ struct MercurialInputScheme : InputScheme
         if (!_input.getRev())
             getCache()->add(
                 store,
-                mutableAttrs,
+                unlockedAttrs,
                 infoAttrs,
                 storePath,
                 false);
 
         getCache()->add(
             store,
-            getImmutableAttrs(),
+            getLockedAttrs(),
             infoAttrs,
             storePath,
             true);

src/libfetchers/path.cc

@@ -80,7 +80,7 @@ struct PathInputScheme : InputScheme
         // nothing to do
     }
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
     {
         std::string absPath;
         auto path = getStrAttr(input.attrs, "path");
@@ -115,10 +115,7 @@ struct PathInputScheme : InputScheme
             // FIXME: try to substitute storePath.
             storePath = store->addToStore("source", absPath);
 
-        return {
-            Tree(store->toRealPath(*storePath), std::move(*storePath)),
-            input
-        };
+        return {std::move(*storePath), input};
     }
 };
 

src/libfetchers/tarball.cc

@@ -13,7 +13,7 @@ DownloadFileResult downloadFile(
     ref<Store> store,
     const std::string & url,
     const std::string & name,
-    bool immutable,
+    bool locked,
     const Headers & headers)
 {
     // FIXME: check store
@@ -67,18 +67,18 @@ DownloadFileResult downloadFile(
         storePath = std::move(cached->storePath);
     } else {
         StringSink sink;
-        dumpString(*res.data, sink);
-        auto hash = hashString(htSHA256, *res.data);
+        dumpString(res.data, sink);
+        auto hash = hashString(htSHA256, res.data);
         ValidPathInfo info {
             store->makeFixedOutputPath(FileIngestionMethod::Flat, hash, name),
-            hashString(htSHA256, *sink.s),
+            hashString(htSHA256, sink.s),
         };
-        info.narSize = sink.s->size();
+        info.narSize = sink.s.size();
         info.ca = FixedOutputHash {
             .method = FileIngestionMethod::Flat,
             .hash = hash,
         };
-        auto source = StringSource { *sink.s };
+        auto source = StringSource(sink.s);
         store->addToStore(info, source, NoRepair, NoCheckSigs);
         storePath = std::move(info.path);
     }
@@ -88,7 +88,7 @@ DownloadFileResult downloadFile(
         inAttrs,
         infoAttrs,
         *storePath,
-        immutable);
+        locked);
 
     if (url != res.effectiveUri)
         getCache()->add(
@@ -100,7 +100,7 @@ DownloadFileResult downloadFile(
             },
             infoAttrs,
             *storePath,
-            immutable);
+            locked);
 
     return {
         .storePath = std::move(*storePath),
@@ -113,7 +113,7 @@ std::pair<Tree, time_t> downloadTarball(
     ref<Store> store,
     const std::string & url,
     const std::string & name,
-    bool immutable,
+    bool locked,
     const Headers & headers)
 {
     Attrs inAttrs({
@@ -126,11 +126,11 @@ std::pair<Tree, time_t> downloadTarball(
 
     if (cached && !cached->expired)
         return {
-            Tree(store->toRealPath(cached->storePath), std::move(cached->storePath)),
+            Tree { .actualPath = store->toRealPath(cached->storePath), .storePath = std::move(cached->storePath) },
             getIntAttr(cached->infoAttrs, "lastModified")
         };
 
-    auto res = downloadFile(store, url, name, immutable, headers);
+    auto res = downloadFile(store, url, name, locked, headers);
 
     std::optional<StorePath> unpackedStorePath;
     time_t lastModified;
@@ -160,10 +160,10 @@ std::pair<Tree, time_t> downloadTarball(
         inAttrs,
         infoAttrs,
         *unpackedStorePath,
-        immutable);
+        locked);
 
     return {
-        Tree(store->toRealPath(*unpackedStorePath), std::move(*unpackedStorePath)),
+        Tree { .actualPath = store->toRealPath(*unpackedStorePath), .storePath = std::move(*unpackedStorePath) },
         lastModified,
     };
 }
@@ -202,7 +202,7 @@ struct TarballInputScheme : InputScheme
 
         Input input;
         input.attrs = attrs;
-        //input.immutable = (bool) maybeGetStrAttr(input.attrs, "hash");
+        //input.locked = (bool) maybeGetStrAttr(input.attrs, "hash");
         return input;
     }
 
@@ -225,10 +225,10 @@ struct TarballInputScheme : InputScheme
         return true;
     }
 
-    std::pair<Tree, Input> fetch(ref<Store> store, const Input & input) override
+    std::pair<StorePath, Input> fetch(ref<Store> store, const Input & input) override
     {
         auto tree = downloadTarball(store, getStrAttr(input.attrs, "url"), input.getName(), false).first;
-        return {std::move(tree), input};
+        return {std::move(tree.storePath), input};
     }
 };
 

src/libmain/common-args.cc

@@ -4,7 +4,7 @@
 
 namespace nix {
 
-MixCommonArgs::MixCommonArgs(const string & programName)
+MixCommonArgs::MixCommonArgs(const std::string & programName)
     : programName(programName)
 {
     addFlag({

src/libmain/common-args.hh

@@ -11,8 +11,8 @@ class MixCommonArgs : public virtual Args
 {
     void initialFlagsProcessed() override;
 public:
-    string programName;
-    MixCommonArgs(const string & programName);
+    std::string programName;
+    MixCommonArgs(const std::string & programName);
 protected:
     virtual void pluginsInited() {}
 };

src/libmain/shared.cc

@@ -94,7 +94,7 @@ void printMissing(ref<Store> store, const StorePathSet & willBuild,
 }
 
 
-string getArg(const string & opt,
+std::string getArg(const std::string & opt,
     Strings::iterator & i, const Strings::iterator & end)
 {
     ++i;
@@ -227,6 +227,8 @@ LegacyArgs::LegacyArgs(const std::string & programName,
     std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg)
     : MixCommonArgs(programName), parseArg(parseArg)
 {
+    printError("FOO %s", programName);
+    
     addFlag({
         .longName = "no-build-output",
         .shortName = 'Q',
@@ -322,14 +324,14 @@ void parseCmdLine(int argc, char * * argv,
 }
 
 
-void parseCmdLine(const string & programName, const Strings & args,
+void parseCmdLine(const std::string & programName, const Strings & args,
     std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg)
 {
     LegacyArgs(programName, parseArg).parseCmdline(args);
 }
 
 
-void printVersion(const string & programName)
+void printVersion(const std::string & programName)
 {
     std::cout << format("%1% (Nix) %2%") % programName % nixVersion << std::endl;
     if (verbosity > lvlInfo) {
@@ -352,7 +354,7 @@ void printVersion(const string & programName)
 }
 
 
-void showManPage(const string & name)
+void showManPage(const std::string & name)
 {
     restoreProcessContext();
     setenv("MANPATH", settings.nixManDir.c_str(), 1);
@@ -361,13 +363,13 @@ void showManPage(const string & name)
 }
 
 
-int handleExceptions(const string & programName, std::function<void()> fun)
+int handleExceptions(const std::string & programName, std::function<void()> fun)
 {
     ReceiveInterrupts receiveInterrupts; // FIXME: need better place for this
 
     ErrorInfo::programName = baseNameOf(programName);
 
-    string error = ANSI_RED "error:" ANSI_NORMAL " ";
+    std::string error = ANSI_RED "error:" ANSI_NORMAL " ";
     try {
         try {
             fun();
@@ -407,7 +409,7 @@ RunPager::RunPager()
     if (!isatty(STDOUT_FILENO)) return;
     char * pager = getenv("NIX_PAGER");
     if (!pager) pager = getenv("PAGER");
-    if (pager && ((string) pager == "" || (string) pager == "cat")) return;
+    if (pager && ((std::string) pager == "" || (std::string) pager == "cat")) return;
 
     Pipe toPager;
     toPager.create();

src/libmain/shared.hh

@@ -22,7 +22,7 @@ public:
     virtual ~Exit();
 };
 
-int handleExceptions(const string & programName, std::function<void()> fun);
+int handleExceptions(const std::string & programName, std::function<void()> fun);
 
 /* Don't forget to call initPlugins() after settings are initialized! */
 void initNix();
@@ -30,10 +30,10 @@ void initNix();
 void parseCmdLine(int argc, char * * argv,
     std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
 
-void parseCmdLine(const string & programName, const Strings & args,
+void parseCmdLine(const std::string & programName, const Strings & args,
     std::function<bool(Strings::iterator & arg, const Strings::iterator & end)> parseArg);
 
-void printVersion(const string & programName);
+void printVersion(const std::string & programName);
 
 /* Ugh.  No better place to put this. */
 void printGCWarning();
@@ -50,10 +50,10 @@ void printMissing(ref<Store> store, const StorePathSet & willBuild,
     const StorePathSet & willSubstitute, const StorePathSet & unknown,
     uint64_t downloadSize, uint64_t narSize, Verbosity lvl = lvlInfo);
 
-string getArg(const string & opt,
+std::string getArg(const std::string & opt,
     Strings::iterator & i, const Strings::iterator & end);
 
-template<class N> N getIntArg(const string & opt,
+template<class N> N getIntArg(const std::string & opt,
     Strings::iterator & i, const Strings::iterator & end, bool allowUnit)
 {
     ++i;
@@ -76,7 +76,7 @@ struct LegacyArgs : public MixCommonArgs
 
 
 /* Show the manual page for the specified program. */
-void showManPage(const string & name);
+void showManPage(const std::string & name);
 
 /* The constructor of this class starts a pager if stdout is a
    terminal and $PAGER is set. Stdout is redirected to the pager. */
@@ -96,7 +96,7 @@ extern volatile ::sig_atomic_t blockInt;
 
 /* GC helpers. */
 
-string showBytes(uint64_t bytes);
+std::string showBytes(uint64_t bytes);
 
 struct GCResults;
 

src/libstore/binary-cache-store.cc

@@ -31,7 +31,7 @@ BinaryCacheStore::BinaryCacheStore(const Params & params)
 
     StringSink sink;
     sink << narVersionMagic1;
-    narMagic = *sink.s;
+    narMagic = sink.s;
 }
 
 void BinaryCacheStore::init()
@@ -68,7 +68,7 @@ void BinaryCacheStore::upsertFile(const std::string & path,
 }
 
 void BinaryCacheStore::getFile(const std::string & path,
-    Callback<std::shared_ptr<std::string>> callback) noexcept
+    Callback<std::optional<std::string>> callback) noexcept
 {
     try {
         callback(getFile(path));
@@ -77,9 +77,9 @@ void BinaryCacheStore::getFile(const std::string & path,
 
 void BinaryCacheStore::getFile(const std::string & path, Sink & sink)
 {
-    std::promise<std::shared_ptr<std::string>> promise;
+    std::promise<std::optional<std::string>> promise;
     getFile(path,
-        {[&](std::future<std::shared_ptr<std::string>> result) {
+        {[&](std::future<std::optional<std::string>> result) {
             try {
                 promise.set_value(result.get());
             } catch (...) {
@@ -89,15 +89,15 @@ void BinaryCacheStore::getFile(const std::string & path, Sink & sink)
     sink(*promise.get_future().get());
 }
 
-std::shared_ptr<std::string> BinaryCacheStore::getFile(const std::string & path)
+std::optional<std::string> BinaryCacheStore::getFile(const std::string & path)
 {
     StringSink sink;
     try {
         getFile(path, sink);
     } catch (NoSuchBinaryCacheFile &) {
-        return nullptr;
+        return std::nullopt;
     }
-    return sink.s;
+    return std::move(sink.s);
 }
 
 std::string BinaryCacheStore::narInfoFileFor(const StorePath & storePath)
@@ -307,7 +307,7 @@ void BinaryCacheStore::addToStore(const ValidPathInfo & info, Source & narSource
     }});
 }
 
-StorePath BinaryCacheStore::addToStoreFromDump(Source & dump, const string & name,
+StorePath BinaryCacheStore::addToStoreFromDump(Source & dump, std::string_view name,
     FileIngestionMethod method, HashType hashAlgo, RepairFlag repair, const StorePathSet & references)
 {
     if (method != FileIngestionMethod::Recursive || hashAlgo != htSHA256)
@@ -367,11 +367,11 @@ void BinaryCacheStore::queryPathInfoUncached(const StorePath & storePath,
     auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
 
     getFile(narInfoFile,
-        {[=](std::future<std::shared_ptr<std::string>> fut) {
+        {[=](std::future<std::optional<std::string>> fut) {
             try {
                 auto data = fut.get();
 
-                if (!data) return (*callbackPtr)(nullptr);
+                if (!data) return (*callbackPtr)({});
 
                 stats.narInfoRead++;
 
@@ -385,8 +385,14 @@ void BinaryCacheStore::queryPathInfoUncached(const StorePath & storePath,
         }});
 }
 
-StorePath BinaryCacheStore::addToStore(const string & name, const Path & srcPath,
-    FileIngestionMethod method, HashType hashAlgo, PathFilter & filter, RepairFlag repair, const StorePathSet & references)
+StorePath BinaryCacheStore::addToStore(
+    std::string_view name,
+    const Path & srcPath,
+    FileIngestionMethod method,
+    HashType hashAlgo,
+    PathFilter & filter,
+    RepairFlag repair,
+    const StorePathSet & references)
 {
     /* FIXME: Make BinaryCacheStore::addToStoreCommon support
        non-recursive+sha256 so we can just use the default
@@ -418,8 +424,11 @@ StorePath BinaryCacheStore::addToStore(const string & name, const Path & srcPath
     })->path;
 }
 
-StorePath BinaryCacheStore::addTextToStore(const string & name, const string & s,
-    const StorePathSet & references, RepairFlag repair)
+StorePath BinaryCacheStore::addTextToStore(
+    std::string_view name,
+    std::string_view s,
+    const StorePathSet & references,
+    RepairFlag repair)
 {
     auto textHash = hashString(htSHA256, s);
     auto path = makeTextPath(name, textHash, references);
@@ -429,7 +438,7 @@ StorePath BinaryCacheStore::addTextToStore(const string & name, const string & s
 
     StringSink sink;
     dumpString(s, sink);
-    auto source = StringSource { *sink.s };
+    StringSource source(sink.s);
     return addToStoreCommon(source, repair, CheckSigs, [&](HashResult nar) {
         ValidPathInfo info { path, nar.first };
         info.narSize = nar.second;
@@ -446,11 +455,11 @@ void BinaryCacheStore::queryRealisationUncached(const DrvOutput & id,
 
     auto callbackPtr = std::make_shared<decltype(callback)>(std::move(callback));
 
-    Callback<std::shared_ptr<std::string>> newCallback = {
-        [=](std::future<std::shared_ptr<std::string>> fut) {
+    Callback<std::optional<std::string>> newCallback = {
+        [=](std::future<std::optional<std::string>> fut) {
             try {
                 auto data = fut.get();
-                if (!data) return (*callbackPtr)(nullptr);
+                if (!data) return (*callbackPtr)({});
 
                 auto realisation = Realisation::fromJSON(
                     nlohmann::json::parse(*data), outputInfoFilePath);
@@ -490,7 +499,7 @@ void BinaryCacheStore::addSignatures(const StorePath & storePath, const StringSe
     writeNarInfo(narInfo);
 }
 
-std::shared_ptr<std::string> BinaryCacheStore::getBuildLog(const StorePath & path)
+std::optional<std::string> BinaryCacheStore::getBuildLog(const StorePath & path)
 {
     auto drvPath = path;
 
@@ -498,10 +507,10 @@ std::shared_ptr<std::string> BinaryCacheStore::getBuildLog(const StorePath & pat
         try {
             auto info = queryPathInfo(path);
             // FIXME: add a "Log" field to .narinfo
-            if (!info->deriver) return nullptr;
+            if (!info->deriver) return std::nullopt;
             drvPath = *info->deriver;
         } catch (InvalidPath &) {
-            return nullptr;
+            return std::nullopt;
         }
     }
 
@@ -512,4 +521,14 @@ std::shared_ptr<std::string> BinaryCacheStore::getBuildLog(const StorePath & pat
     return getFile(logPath);
 }
 
+void BinaryCacheStore::addBuildLog(const StorePath & drvPath, std::string_view log)
+{
+    assert(drvPath.isDerivation());
+
+    upsertFile(
+        "log/" + std::string(drvPath.to_string()),
+        (std::string) log, // FIXME: don't copy
+        "text/plain; charset=utf-8");
+}
+
 }

src/libstore/binary-cache-store.hh

@@ -51,6 +51,7 @@ public:
         const std::string & mimeType) = 0;
 
     void upsertFile(const std::string & path,
+        // FIXME: use std::string_view
         std::string && data,
         const std::string & mimeType);
 
@@ -62,10 +63,11 @@ public:
 
     /* Fetch the specified file and call the specified callback with
        the result. A subclass may implement this asynchronously. */
-    virtual void getFile(const std::string & path,
-        Callback<std::shared_ptr<std::string>> callback) noexcept;
+    virtual void getFile(
+        const std::string & path,
+        Callback<std::optional<std::string>> callback) noexcept;
 
-    std::shared_ptr<std::string> getFile(const std::string & path);
+    std::optional<std::string> getFile(const std::string & path);
 
 public:
 
@@ -96,15 +98,23 @@ public:
     void addToStore(const ValidPathInfo & info, Source & narSource,
         RepairFlag repair, CheckSigsFlag checkSigs) override;
 
-    StorePath addToStoreFromDump(Source & dump, const string & name,
+    StorePath addToStoreFromDump(Source & dump, std::string_view name,
         FileIngestionMethod method, HashType hashAlgo, RepairFlag repair, const StorePathSet & references) override;
 
-    StorePath addToStore(const string & name, const Path & srcPath,
-        FileIngestionMethod method, HashType hashAlgo,
-        PathFilter & filter, RepairFlag repair, const StorePathSet & references) override;
+    StorePath addToStore(
+        std::string_view name,
+        const Path & srcPath,
+        FileIngestionMethod method,
+        HashType hashAlgo,
+        PathFilter & filter,
+        RepairFlag repair,
+        const StorePathSet & references) override;
 
-    StorePath addTextToStore(const string & name, const string & s,
-        const StorePathSet & references, RepairFlag repair) override;
+    StorePath addTextToStore(
+        std::string_view name,
+        std::string_view s,
+        const StorePathSet & references,
+        RepairFlag repair) override;
 
     void registerDrvOutput(const Realisation & info) override;
 
@@ -117,7 +127,9 @@ public:
 
     void addSignatures(const StorePath & storePath, const StringSet & sigs) override;
 
-    std::shared_ptr<std::string> getBuildLog(const StorePath & path) override;
+    std::optional<std::string> getBuildLog(const StorePath & path) override;
+
+    void addBuildLog(const StorePath & drvPath, std::string_view log) override;
 
 };
 

src/libstore/build/derivation-goal.cc

@@ -116,7 +116,7 @@ DerivationGoal::~DerivationGoal()
 }
 
 
-string DerivationGoal::key()
+std::string DerivationGoal::key()
 {
     /* Ensure that derivations get built in order of their name,
        i.e. a derivation named "aardvark" always comes before
@@ -278,7 +278,7 @@ void DerivationGoal::outputsSubstitutionTried()
 
     if (nrFailed > 0 && nrFailed > nrNoSubstituters + nrIncompleteClosure && !settings.tryFallback) {
         done(BuildResult::TransientFailure,
-            fmt("some substitutes for the outputs of derivation '%s' failed (usually happens due to networking issues); try '--fallback' to build derivation from source ",
+            Error("some substitutes for the outputs of derivation '%s' failed (usually happens due to networking issues); try '--fallback' to build derivation from source ",
                 worker.store.printStorePath(drvPath)));
         return;
     }
@@ -1024,7 +1024,7 @@ HookReply DerivationGoal::tryBuildHook()
 
         /* Read the first line of input, which should be a word indicating
            whether the hook wishes to perform the build. */
-        string reply;
+        std::string reply;
         while (true) {
             auto s = [&]() {
                 try {
@@ -1036,8 +1036,8 @@ HookReply DerivationGoal::tryBuildHook()
             }();
             if (handleJSONLogMessage(s, worker.act, worker.hook->activities, true))
                 ;
-            else if (string(s, 0, 2) == "# ") {
-                reply = string(s, 2);
+            else if (s.substr(0, 2) == "# ") {
+                reply = s.substr(2);
                 break;
             }
             else {
@@ -1102,7 +1102,7 @@ HookReply DerivationGoal::tryBuildHook()
     /* Create the log file and pipe. */
     Path logFile = openLogFile();
 
-    set<int> fds;
+    std::set<int> fds;
     fds.insert(hook->fromHook.readSide.get());
     fds.insert(hook->builderOut.readSide.get());
     worker.childStarted(shared_from_this(), fds, false, false);
@@ -1151,10 +1151,10 @@ Path DerivationGoal::openLogFile()
         logDir = localStore->logDir;
     else
         logDir = settings.nixLogDir;
-    Path dir = fmt("%s/%s/%s/", logDir, LocalFSStore::drvsLogDir, string(baseName, 0, 2));
+    Path dir = fmt("%s/%s/%s/", logDir, LocalFSStore::drvsLogDir, baseName.substr(0, 2));
     createDirs(dir);
 
-    Path logFileName = fmt("%s/%s%s", dir, string(baseName, 2),
+    Path logFileName = fmt("%s/%s%s", dir, baseName.substr(2),
         settings.compressLog ? ".bz2" : "");
 
     fdLogFile = open(logFileName.c_str(), O_CREAT | O_WRONLY | O_TRUNC | O_CLOEXEC, 0666);
@@ -1187,7 +1187,7 @@ bool DerivationGoal::isReadDesc(int fd)
 }
 
 
-void DerivationGoal::handleChildOutput(int fd, const string & data)
+void DerivationGoal::handleChildOutput(int fd, std::string_view data)
 {
     if (isReadDesc(fd))
     {

src/libstore/build/derivation-goal.hh

@@ -150,7 +150,7 @@ struct DerivationGoal : public Goal
 
     void timedOut(Error && ex) override;
 
-    string key() override;
+    std::string key() override;
 
     void work() override;
 
@@ -205,7 +205,7 @@ struct DerivationGoal : public Goal
     virtual bool isReadDesc(int fd);
 
     /* Callback used by the worker to write to the log. */
-    void handleChildOutput(int fd, const string & data) override;
+    void handleChildOutput(int fd, std::string_view data) override;
     void handleEOF(int fd) override;
     void flushLine();
 

src/libstore/build/drv-output-substitution-goal.cc

@@ -137,7 +137,7 @@ void DrvOutputSubstitutionGoal::finished()
     amDone(ecSuccess);
 }
 
-string DrvOutputSubstitutionGoal::key()
+std::string DrvOutputSubstitutionGoal::key()
 {
     /* "a$" ensures substitution goals happen before derivation
        goals. */

src/libstore/build/drv-output-substitution-goal.hh

@@ -51,7 +51,7 @@ public:
 
     void timedOut(Error && ex) override { abort(); };
 
-    string key() override;
+    std::string key() override;
 
     void work() override;
     void handleEOF(int fd) override;

src/libstore/build/goal.cc

@@ -5,8 +5,8 @@ namespace nix {
 
 
 bool CompareGoalPtrs::operator() (const GoalPtr & a, const GoalPtr & b) const {
-    string s1 = a->key();
-    string s2 = b->key();
+    std::string s1 = a->key();
+    std::string s2 = b->key();
     return s1 < s2;
 }
 

src/libstore/build/goal.hh

@@ -18,8 +18,8 @@ struct CompareGoalPtrs {
 };
 
 /* Set of goals. */
-typedef set<GoalPtr, CompareGoalPtrs> Goals;
-typedef set<WeakGoalPtr, std::owner_less<WeakGoalPtr>> WeakGoals;
+typedef std::set<GoalPtr, CompareGoalPtrs> Goals;
+typedef std::set<WeakGoalPtr, std::owner_less<WeakGoalPtr>> WeakGoals;
 
 /* A map of paths to goals (and the other way around). */
 typedef std::map<StorePath, WeakGoalPtr> WeakGoalMap;
@@ -50,7 +50,7 @@ struct Goal : public std::enable_shared_from_this<Goal>
     unsigned int nrIncompleteClosure;
 
     /* Name of this goal for debugging purposes. */
-    string name;
+    std::string name;
 
     /* Whether the goal is finished. */
     ExitCode exitCode;
@@ -75,7 +75,7 @@ struct Goal : public std::enable_shared_from_this<Goal>
 
     virtual void waiteeDone(GoalPtr waitee, ExitCode result);
 
-    virtual void handleChildOutput(int fd, const string & data)
+    virtual void handleChildOutput(int fd, std::string_view data)
     {
         abort();
     }
@@ -87,7 +87,7 @@ struct Goal : public std::enable_shared_from_this<Goal>
 
     void trace(const FormatOrString & fs);
 
-    string getName()
+    std::string getName()
     {
         return name;
     }
@@ -97,7 +97,7 @@ struct Goal : public std::enable_shared_from_this<Goal>
        by the worker (important!), etc. */
     virtual void timedOut(Error && ex) = 0;
 
-    virtual string key() = 0;
+    virtual std::string key() = 0;
 
     void amDone(ExitCode result, std::optional<Error> ex = {});
 

src/libstore/build/local-derivation-goal.cc

@@ -481,12 +481,12 @@ void LocalDerivationGoal::startBuilder()
            temporary build directory.  The text files have the format used
            by `nix-store --register-validity'.  However, the deriver
            fields are left empty. */
-        string s = get(drv->env, "exportReferencesGraph").value_or("");
+        auto s = get(drv->env, "exportReferencesGraph").value_or("");
         Strings ss = tokenizeString<Strings>(s);
         if (ss.size() % 2 != 0)
             throw BuildError("odd number of tokens in 'exportReferencesGraph': '%1%'", s);
         for (Strings::iterator i = ss.begin(); i != ss.end(); ) {
-            string fileName = *i++;
+            auto fileName = *i++;
             static std::regex regex("[A-Za-z_][A-Za-z0-9_.-]*");
             if (!std::regex_match(fileName, regex))
                 throw Error("invalid file name '%s' in 'exportReferencesGraph'", fileName);
@@ -517,10 +517,10 @@ void LocalDerivationGoal::startBuilder()
                 i.pop_back();
             }
             size_t p = i.find('=');
-            if (p == string::npos)
+            if (p == std::string::npos)
                 dirsInChroot[i] = {i, optional};
             else
-                dirsInChroot[string(i, 0, p)] = {string(i, p + 1), optional};
+                dirsInChroot[i.substr(0, p)] = {i.substr(p + 1), optional};
         }
         dirsInChroot[tmpDirInSandbox] = tmpDir;
 
@@ -671,9 +671,10 @@ void LocalDerivationGoal::startBuilder()
         auto state = stBegin;
         auto lines = runProgram(settings.preBuildHook, false, args);
         auto lastPos = std::string::size_type{0};
-        for (auto nlPos = lines.find('\n'); nlPos != string::npos;
-                nlPos = lines.find('\n', lastPos)) {
-            auto line = std::string{lines, lastPos, nlPos - lastPos};
+        for (auto nlPos = lines.find('\n'); nlPos != std::string::npos;
+                nlPos = lines.find('\n', lastPos))
+        {
+            auto line = lines.substr(lastPos, nlPos - lastPos);
             lastPos = nlPos + 1;
             if (state == stBegin) {
                 if (line == "extra-sandbox-paths" || line == "extra-chroot-dirs") {
@@ -686,10 +687,10 @@ void LocalDerivationGoal::startBuilder()
                     state = stBegin;
                 } else {
                     auto p = line.find('=');
-                    if (p == string::npos)
+                    if (p == std::string::npos)
                         dirsInChroot[line] = line;
                     else
-                        dirsInChroot[string(line, 0, p)] = string(line, p + 1);
+                        dirsInChroot[line.substr(0, p)] = line.substr(p + 1);
                 }
             }
         }
@@ -913,9 +914,12 @@ void LocalDerivationGoal::startBuilder()
         sandboxMountNamespace = open(fmt("/proc/%d/ns/mnt", (pid_t) pid).c_str(), O_RDONLY);
         if (sandboxMountNamespace.get() == -1)
             throw SysError("getting sandbox mount namespace");
+
+        if (usingUserNamespace) {
             sandboxUserNamespace = open(fmt("/proc/%d/ns/user", (pid_t) pid).c_str(), O_RDONLY);
             if (sandboxUserNamespace.get() == -1)
                 throw SysError("getting sandbox user namespace");
+        }
 
         /* Signal the builder that we've updated its user namespace. */
         writeFull(userNamespaceSync.writeSide.get(), "1");
@@ -939,7 +943,7 @@ void LocalDerivationGoal::startBuilder()
     /* Check if setting up the build environment failed. */
     std::vector<std::string> msgs;
     while (true) {
-        string msg = [&]() {
+        std::string msg = [&]() {
             try {
                 return readLine(builderOut.readSide.get());
             } catch (Error & e) {
@@ -951,8 +955,8 @@ void LocalDerivationGoal::startBuilder()
                 throw;
             }
         }();
-        if (string(msg, 0, 1) == "\2") break;
-        if (string(msg, 0, 1) == "\1") {
+        if (msg.substr(0, 1) == "\2") break;
+        if (msg.substr(0, 1) == "\1") {
             FdSource source(builderOut.readSide.get());
             auto ex = readError(source);
             ex.addTrace({}, "while setting up the build environment");
@@ -988,7 +992,7 @@ void LocalDerivationGoal::initTmpDir() {
                 env[i.first] = i.second;
             } else {
                 auto hash = hashString(htSHA256, i.first);
-                string fn = ".attr-" + hash.to_string(Base32, false);
+                std::string fn = ".attr-" + hash.to_string(Base32, false);
                 Path p = tmpDir + "/" + fn;
                 writeFile(p, rewriteStrings(i.second, inputRewrites));
                 chownToBuilder(p);
@@ -1079,7 +1083,7 @@ void LocalDerivationGoal::writeStructuredAttrs()
         for (auto & [i, v] : json["outputs"].get<nlohmann::json::object_t>()) {
             /* The placeholder must have a rewrite, so we use it to cover both the
                cases where we know or don't know the output path ahead of time. */
-            rewritten[i] = rewriteStrings(v, inputRewrites);
+            rewritten[i] = rewriteStrings((std::string) v, inputRewrites);
         }
 
         json["outputs"] = rewritten;
@@ -1185,10 +1189,14 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
     std::optional<StorePath> queryPathFromHashPart(const std::string & hashPart) override
     { throw Error("queryPathFromHashPart"); }
 
-    StorePath addToStore(const string & name, const Path & srcPath,
-        FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256,
-        PathFilter & filter = defaultPathFilter, RepairFlag repair = NoRepair,
-        const StorePathSet & references = StorePathSet()) override
+    StorePath addToStore(
+        std::string_view name,
+        const Path & srcPath,
+        FileIngestionMethod method,
+        HashType hashAlgo,
+        PathFilter & filter,
+        RepairFlag repair,
+        const StorePathSet & references) override
     { throw Error("addToStore"); }
 
     void addToStore(const ValidPathInfo & info, Source & narSource,
@@ -1198,17 +1206,24 @@ struct RestrictedStore : public virtual RestrictedStoreConfig, public virtual Lo
         goal.addDependency(info.path);
     }
 
-    StorePath addTextToStore(const string & name, const string & s,
-        const StorePathSet & references, RepairFlag repair = NoRepair) override
+    StorePath addTextToStore(
+        std::string_view name,
+        std::string_view s,
+        const StorePathSet & references,
+        RepairFlag repair = NoRepair) override
     {
         auto path = next->addTextToStore(name, s, references, repair);
         goal.addDependency(path);
         return path;
     }
 
-    StorePath addToStoreFromDump(Source & dump, const string & name,
-        FileIngestionMethod method = FileIngestionMethod::Recursive, HashType hashAlgo = htSHA256, RepairFlag repair = NoRepair,
-        const StorePathSet & references = StorePathSet()) override
+    StorePath addToStoreFromDump(
+        Source & dump,
+        std::string_view name,
+        FileIngestionMethod method,
+        HashType hashAlgo,
+        RepairFlag repair,
+        const StorePathSet & references) override
     {
         auto path = next->addToStoreFromDump(dump, name, method, hashAlgo, repair, references);
         goal.addDependency(path);
@@ -1428,7 +1443,7 @@ void LocalDerivationGoal::addDependency(const StorePath & path)
 
             Path source = worker.store.Store::toRealPath(path);
             Path target = chrootRootDir + worker.store.printStorePath(path);
-            debug("bind-mounting %s -> %s", source, target);
+            debug("bind-mounting %s -> %s", target, source);
 
             if (pathExists(target))
                 throw Error("store path '%s' already exists in the sandbox", worker.store.printStorePath(path));
@@ -1990,7 +2005,7 @@ void LocalDerivationGoal::runChild()
             args.push_back(rewriteStrings(i, inputRewrites));
 
         /* Indicate that we managed to set up the build environment. */
-        writeFull(STDERR_FILENO, string("\2\n"));
+        writeFull(STDERR_FILENO, std::string("\2\n"));
 
         /* Execute the program.  This should not return. */
         if (drv->isBuiltin()) {
@@ -2008,7 +2023,7 @@ void LocalDerivationGoal::runChild()
                 else if (drv->builder == "builtin:unpack-channel")
                     builtinUnpackChannel(drv2);
                 else
-                    throw Error("unsupported builtin builder '%1%'", string(drv->builder, 8));
+                    throw Error("unsupported builtin builder '%1%'", drv->builder.substr(8));
                 _exit(0);
             } catch (std::exception & e) {
                 writeFull(STDERR_FILENO, e.what() + std::string("\n"));
@@ -2227,8 +2242,8 @@ void LocalDerivationGoal::registerOutputs()
                 StringSink sink;
                 dumpPath(actualPath, sink);
                 deletePath(actualPath);
-                sink.s = make_ref<std::string>(rewriteStrings(*sink.s, outputRewrites));
-                StringSource source(*sink.s);
+                sink.s = rewriteStrings(sink.s, outputRewrites);
+                StringSource source(sink.s);
                 restorePath(actualPath, source);
             }
         };
@@ -2296,7 +2311,7 @@ void LocalDerivationGoal::registerOutputs()
                     StringSink sink;
                     dumpPath(actualPath, sink);
                     RewritingSink rsink2(oldHashPart, std::string(finalPath.hashPart()), nextSink);
-                    rsink2(*sink.s);
+                    rsink2(sink.s);
                     rsink2.flush();
                 });
                 Path tmpPath = actualPath + ".tmp";
@@ -2468,7 +2483,7 @@ void LocalDerivationGoal::registerOutputs()
         }
 
         if (curRound == nrRounds) {
-            localStore.optimisePath(actualPath); // FIXME: combine with scanForReferences()
+            localStore.optimisePath(actualPath, NoRepair); // FIXME: combine with scanForReferences()
             worker.markContentsGood(newInfo.path);
         }
 
@@ -2692,7 +2707,7 @@ void LocalDerivationGoal::checkOutputs(const std::map<Path, ValidPathInfo> & out
                     }
 
                 if (!badPaths.empty()) {
-                    string badPathsStr;
+                    std::string badPathsStr;
                     for (auto & i : badPaths) {
                         badPathsStr += "\n  ";
                         badPathsStr += worker.store.printStorePath(i);

src/libstore/build/local-derivation-goal.hh

@@ -58,7 +58,7 @@ struct LocalDerivationGoal : public DerivationGoal
     typedef map<Path, ChrootPath> DirsInChroot; // maps target path to source path
     DirsInChroot dirsInChroot;
 
-    typedef map<string, string> Environment;
+    typedef map<std::string, std::string> Environment;
     Environment env;
 
 #if __APPLE__