Build a minimized Nix with MinGW

At this point many features are stripped out, but this works:

- Can run libnix{util,store,expr} unit tests
- Can run some Nix commands

Co-Authored-By volth <volth@volth.com>
Co-Authored-By Brian McKenna <brian@brianmckenna.org>

src/libstore/builtins/buildenv.cc

@@ -76,7 +76,11 @@ static void createLinks(State & state, const Path & srcDir, const Path & dstDir,
                         throw Error("collision between '%1%' and non-directory '%2%'", srcFile, target);
                     if (unlink(dstFile.c_str()) == -1)
                         throw SysError("unlinking '%1%'", dstFile);
-                    if (mkdir(dstFile.c_str(), 0755) == -1)
+                    if (mkdir(dstFile.c_str()
+                #ifndef _WIN32 // TODO abstract mkdir perms for Windows
+                            , 0755
+                #endif
+                            ) == -1)
                         throw SysError("creating directory '%1%'", dstFile);
                     createLinks(state, target, dstFile, state.priorities[dstFile]);
                     createLinks(state, srcFile, dstFile, priority);

src/libstore/daemon.cc

@@ -1,5 +1,4 @@
 #include "daemon.hh"
-#include "monitor-fd.hh"
 #include "signals.hh"
 #include "worker-protocol.hh"
 #include "worker-protocol-impl.hh"
@@ -16,6 +15,10 @@
 #include "args.hh"
 #include "git.hh"
 
+#ifndef _WIN32 // TODO need graceful async exit support on Windows?
+# include "monitor-fd.hh"
+#endif
+
 namespace nix::daemon {
 
 Sink & operator << (Sink & sink, const Logger::Fields & fields)
@@ -1018,7 +1021,9 @@ void processConnection(
     TrustedFlag trusted,
     RecursiveFlag recursive)
 {
+#ifndef _WIN32 // TODO need graceful async exit support on Windows?
     auto monitor = !recursive ? std::make_unique<MonitorFdHup>(from.fd) : nullptr;
+#endif
 
     /* Exchange the greeting. */
     unsigned int magic = readInt(from);

src/libstore/filetransfer.cc

@@ -516,10 +516,12 @@ struct curlFileTransfer : public FileTransfer
 
     Sync<State> state_;
 
+    #ifndef _WIN32 // TODO need graceful async exit support on Windows?
     /* We can't use a std::condition_variable to wake up the curl
        thread, because it only monitors file descriptors. So use a
        pipe instead. */
     Pipe wakeupPipe;
+    #endif
 
     std::thread workerThread;
 
@@ -539,8 +541,10 @@ struct curlFileTransfer : public FileTransfer
             fileTransferSettings.httpConnections.get());
         #endif
 
+        #ifndef _WIN32 // TODO need graceful async exit support on Windows?
         wakeupPipe.create();
         fcntl(wakeupPipe.readSide.get(), F_SETFL, O_NONBLOCK);
+        #endif
 
         workerThread = std::thread([&]() { workerThreadEntry(); });
     }
@@ -561,15 +565,19 @@ struct curlFileTransfer : public FileTransfer
             auto state(state_.lock());
             state->quit = true;
         }
+        #ifndef _WIN32 // TODO need graceful async exit support on Windows?
         writeFull(wakeupPipe.writeSide.get(), " ", false);
+        #endif
     }
 
     void workerThreadMain()
     {
         /* Cause this thread to be notified on SIGINT. */
+        #ifndef _WIN32 // TODO need graceful async exit support on Windows?
         auto callback = createInterruptCallback([&]() {
             stopWorkerThread();
         });
+        #endif
 
         #if __linux__
         unshareFilesystem();
@@ -607,9 +615,11 @@ struct curlFileTransfer : public FileTransfer
             /* Wait for activity, including wakeup events. */
             int numfds = 0;
             struct curl_waitfd extraFDs[1];
+            #ifndef _WIN32 // TODO need graceful async exit support on Windows?
             extraFDs[0].fd = wakeupPipe.readSide.get();
             extraFDs[0].events = CURL_WAIT_POLLIN;
             extraFDs[0].revents = 0;
+            #endif
             long maxSleepTimeMs = items.empty() ? 10000 : 100;
             auto sleepTimeMs =
                 nextWakeup != std::chrono::steady_clock::time_point()
@@ -693,7 +703,9 @@ struct curlFileTransfer : public FileTransfer
                 throw nix::Error("cannot enqueue download request because the download thread is shutting down");
             state->incoming.push(item);
         }
+        #ifndef _WIN32 // TODO need graceful async exit support on Windows?
         writeFull(wakeupPipe.writeSide.get(), " ");
+        #endif
     }
 
 #if ENABLE_S3

src/libstore/globals.cc

@@ -9,11 +9,14 @@
 #include <map>
 #include <mutex>
 #include <thread>
-#include <dlfcn.h>
-#include <sys/utsname.h>
 
 #include <nlohmann/json.hpp>
 
+#ifndef _WIN32
+# include <dlfcn.h>
+# include <sys/utsname.h>
+#endif
+
 #ifdef __GLIBC__
 # include <gnu/lib-names.h>
 # include <nss.h>
@@ -56,7 +59,9 @@ Settings::Settings()
     , nixManDir(canonPath(NIX_MAN_DIR))
     , nixDaemonSocketFile(canonPath(getEnvNonEmpty("NIX_DAEMON_SOCKET_PATH").value_or(nixStateDir + DEFAULT_SOCKET_PATH)))
 {
+#ifndef _WIN32
     buildUsersGroup = isRootUser() ? "nixbld" : "";
+#endif
     allowSymlinkedStore = getEnv("NIX_IGNORE_SYMLINK_STORE") == "1";
 
     auto sslOverride = getEnv("NIX_SSL_CERT_FILE").value_or(getEnv("SSL_CERT_FILE").value_or(""));
@@ -239,11 +244,15 @@ StringSet Settings::getDefaultExtraPlatforms()
 
 bool Settings::isWSL1()
 {
+#if __linux__
     struct utsname utsbuf;
     uname(&utsbuf);
     // WSL1 uses -Microsoft suffix
     // WSL2 uses -microsoft-standard suffix
     return hasSuffix(utsbuf.release, "-Microsoft");
+#else
+    return false;
+#endif
 }
 
 Path Settings::getDefaultSSLCertFile()
@@ -341,6 +350,7 @@ void initPlugins()
         for (const auto & file : pluginFiles) {
             /* handle is purposefully leaked as there may be state in the
                DSO needed by the action of the plugin. */
+#ifndef _WIN32 // TODO implement via DLL loading on Windows
             void *handle =
                 dlopen(file.c_str(), RTLD_LAZY | RTLD_LOCAL);
             if (!handle)
@@ -351,6 +361,9 @@ void initPlugins()
             void (*nix_plugin_entry)() = (void (*)())dlsym(handle, "nix_plugin_entry");
             if (nix_plugin_entry)
                 nix_plugin_entry();
+#else
+                throw Error("could not dynamically open plugin file '%s'", file);
+#endif
         }
     }
 

src/libstore/globals.hh

@@ -666,6 +666,7 @@ public:
     Setting<bool> sandboxFallback{this, true, "sandbox-fallback",
         "Whether to disable sandboxing when the kernel doesn't allow it."};
 
+#ifndef _WIN32
     Setting<bool> requireDropSupplementaryGroups{this, isRootUser(), "require-drop-supplementary-groups",
         R"(
           Following the principle of least privilege,
@@ -683,6 +684,7 @@ public:
           (since `root` usually has permissions to call setgroups)
           and `false` otherwise.
         )"};
+#endif
 
 #if __linux__
     Setting<std::string> sandboxShmSize{

src/libstore/local.mk

@@ -4,9 +4,12 @@ libstore_NAME = libnixstore
 
 libstore_DIR := $(d)
 
-libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
+libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc)
 ifdef HOST_UNIX
-  libstore_SOURCES += $(wildcard $(d)/unix/*.cc)
+  libstore_SOURCES += $(wildcard $(d)/unix/*.cc $(d)/unix/builtins/*.cc $(d)/unix/build/*.cc)
+endif
+ifdef HOST_WINDOWS
+  libstore_SOURCES += $(wildcard $(d)/windows/*.cc)
 endif
 
 libstore_LIBS = libutil
@@ -55,9 +58,9 @@ libstore_CXXFLAGS += \
 ifeq ($(embedded_sandbox_shell),yes)
 libstore_CXXFLAGS += -DSANDBOX_SHELL=\"__embedded_sandbox_shell__\"
 
-$(d)/build/local-derivation-goal.cc: $(d)/embedded-sandbox-shell.gen.hh
+$(d)/unix/build/local-derivation-goal.cc: $(d)/unix/embedded-sandbox-shell.gen.hh
 
-$(d)/embedded-sandbox-shell.gen.hh: $(sandbox_shell)
+$(d)/unix/embedded-sandbox-shell.gen.hh: $(sandbox_shell)
 	$(trace-gen) hexdump -v -e '1/1 "0x%x," "\n"' < $< > $@.tmp
 	@mv $@.tmp $@
 else
@@ -66,11 +69,11 @@ else
   endif
 endif
 
-$(d)/local-store.cc: $(d)/schema.sql.gen.hh $(d)/ca-specific-schema.sql.gen.hh
+$(d)/unix/local-store.cc: $(d)/unix/schema.sql.gen.hh $(d)/unix/ca-specific-schema.sql.gen.hh
 
-$(d)/build.cc:
+$(d)/unix/build.cc:
 
-clean-files += $(d)/schema.sql.gen.hh $(d)/ca-specific-schema.sql.gen.hh
+clean-files += $(d)/unix/schema.sql.gen.hh $(d)/unix/ca-specific-schema.sql.gen.hh
 
 $(eval $(call install-file-in, $(buildprefix)$(d)/nix-store.pc, $(libdir)/pkgconfig, 0644))
 

src/libstore/misc.cc

@@ -1,7 +1,6 @@
 #include "derivations.hh"
 #include "parsed-derivations.hh"
 #include "globals.hh"
-#include "local-store.hh"
 #include "store-api.hh"
 #include "thread-pool.hh"
 #include "realisation.hh"

src/libstore/profiles.hh

@@ -8,6 +8,7 @@
 #include "types.hh"
 #include "pathlocks.hh"
 
+#include <optional>
 #include <time.h>
 
 

src/libstore/remote-fs-accessor.cc

@@ -71,11 +71,15 @@ std::pair<ref<SourceAccessor>, CanonPath> RemoteFSAccessor::fetch(const CanonPat
             auto narAccessor = makeLazyNarAccessor(listing,
                 [cacheFile](uint64_t offset, uint64_t length) {
 
-                    AutoCloseFD fd = open(cacheFile.c_str(), O_RDONLY | O_CLOEXEC);
+                    AutoCloseFD fd = toDescriptor(open(cacheFile.c_str(), O_RDONLY
+                    #ifndef _WIN32
+                        | O_CLOEXEC
+                    #endif
+                        ));
                     if (!fd)
                         throw SysError("opening NAR cache file '%s'", cacheFile);
 
-                    if (lseek(fd.get(), offset, SEEK_SET) != (off_t) offset)
+                    if (lseek(fromDescriptorReadOnly(fd.get()), offset, SEEK_SET) != (off_t) offset)
                         throw SysError("seeking in '%s'", cacheFile);
 
                     std::string buf(length, 0);

src/libstore/ssh.cc

@@ -55,6 +55,9 @@ bool SSHMaster::isMasterRunning() {
 std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(
     Strings && command, Strings && extraSshArgs)
 {
+#ifdef _WIN32 // TODO re-enable on Windows, once we can start processes.
+    throw UnimplementedError("cannot yet SSH on windows because spawning processes is not yet implemented");
+#else
     Path socketPath = startMaster();
 
     Pipe in, out;
@@ -105,8 +108,8 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(
     }, options);
 
 
-    in.readSide = -1;
-    out.writeSide = -1;
+    in.readSide = INVALID_DESCRIPTOR;
+    out.writeSide = INVALID_DESCRIPTOR;
 
     // Wait for the SSH connection to be established,
     // So that we don't overwrite the password prompt with our progress bar.
@@ -126,15 +129,18 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(
     conn->in = std::move(in.writeSide);
 
     return conn;
+#endif
 }
 
+#ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
+
 Path SSHMaster::startMaster()
 {
     if (!useMaster) return "";
 
     auto state(state_.lock());
 
-    if (state->sshMaster != -1) return state->socketPath;
+    if (state->sshMaster != INVALID_DESCRIPTOR) return state->socketPath;
 
     state->socketPath = (Path) *state->tmpDir + "/ssh.sock";
 
@@ -167,7 +173,7 @@ Path SSHMaster::startMaster()
         throw SysError("unable to execute '%s'", args.front());
     }, options);
 
-    out.writeSide = -1;
+    out.writeSide = INVALID_DESCRIPTOR;
 
     std::string reply;
     try {
@@ -182,4 +188,6 @@ Path SSHMaster::startMaster()
     return state->socketPath;
 }
 
+#endif
+
 }

src/libstore/ssh.hh

@@ -21,7 +21,9 @@ private:
 
     struct State
     {
+#ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
         Pid sshMaster;
+#endif
         std::unique_ptr<AutoDelete> tmpDir;
         Path socketPath;
     };
@@ -31,13 +33,19 @@ private:
     void addCommonSSHOpts(Strings & args);
     bool isMasterRunning();
 
+#ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
+    Path startMaster();
+#endif
+
 public:
 
     SSHMaster(const std::string & host, const std::string & keyFile, const std::string & sshPublicHostKey, bool useMaster, bool compress, int logFD = -1);
 
     struct Connection
     {
+#ifndef _WIN32 // TODO re-enable on Windows, once we can start processes.
         Pid sshPid;
+#endif
         AutoCloseFD out, in;
     };
 
@@ -51,8 +59,6 @@ public:
     std::unique_ptr<Connection> startCommand(
         Strings && command,
         Strings && extraSshArgs = {});
-
-    Path startMaster();
 };
 
 }

src/libstore/store-api.cc

@@ -13,7 +13,6 @@
 #include "archive.hh"
 #include "callback.hh"
 #include "git.hh"
-#include "remote-store.hh"
 #include "posix-source-accessor.hh"
 // FIXME this should not be here, see TODO below on
 // `addMultipleToStore`.
@@ -21,6 +20,10 @@
 #include "signals.hh"
 #include "users.hh"
 
+#ifndef _WIN32
+# include "remote-store.hh"
+#endif
+
 #include <nlohmann/json.hpp>
 #include <regex>
 
@@ -1266,9 +1269,10 @@ Derivation Store::readInvalidDerivation(const StorePath & drvPath)
 
 }
 
-
-#include "local-store.hh"
-#include "uds-remote-store.hh"
+#ifndef _WIN32
+# include "local-store.hh"
+# include "uds-remote-store.hh"
+#endif
 
 
 namespace nix {
@@ -1286,6 +1290,9 @@ std::pair<std::string, Store::Params> splitUriAndParams(const std::string & uri_
     return {uri, params};
 }
 
+#ifdef _WIN32 // Unused on Windows because the next `#ifndef`
+[[maybe_unused]]
+#endif
 static bool isNonUriPath(const std::string & spec)
 {
     return
@@ -1298,6 +1305,9 @@ static bool isNonUriPath(const std::string & spec)
 
 std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Params & params)
 {
+    // TODO reenable on Windows once we have `LocalStore` and
+    // `UDSRemoteStore`.
+    #ifndef _WIN32
     if (uri == "" || uri == "auto") {
         auto stateDir = getOr(params, "state", settings.nixStateDir);
         if (access(stateDir.c_str(), R_OK | W_OK) == 0)
@@ -1342,6 +1352,9 @@ std::shared_ptr<Store> openFromNonUri(const std::string & uri, const Store::Para
     } else {
         return nullptr;
     }
+    #else
+    return nullptr;
+    #endif
 }
 
 // The `parseURL` function supports both IPv6 URIs as defined in

src/libstore/windows/build.cc

@@ -0,0 +1,37 @@
+#include "store-api.hh"
+#include "build-result.hh"
+
+namespace nix {
+
+void Store::buildPaths(const std::vector<DerivedPath> & reqs, BuildMode buildMode, std::shared_ptr<Store> evalStore)
+{
+    unsupported("buildPaths");
+}
+
+std::vector<KeyedBuildResult> Store::buildPathsWithResults(
+    const std::vector<DerivedPath> & reqs,
+    BuildMode buildMode,
+    std::shared_ptr<Store> evalStore)
+{
+    unsupported("buildPathsWithResults");
+}
+
+BuildResult Store::buildDerivation(const StorePath & drvPath, const BasicDerivation & drv,
+    BuildMode buildMode)
+{
+    unsupported("buildDerivation");
+}
+
+
+void Store::ensurePath(const StorePath & path)
+{
+    unsupported("ensurePath");
+}
+
+
+void Store::repairPath(const StorePath & path)
+{
+    unsupported("repairPath");
+}
+
+}