Use the standalone gc lib in the default gc

src/libstore/gc.cc

@@ -3,6 +3,7 @@
 #include "local-store.hh"
 #include "local-fs-store.hh"
 #include "finally.hh"
+#include "find-roots.hh"
 
 #include <functional>
 #include <queue>
@@ -284,14 +285,28 @@ void LocalStore::findRootsNoTempNoExternalDaemon(Roots & roots, bool censor)
 {
     debug("Can’t connect to the tracing daemon socket, fallback to the internal trace");
 
-    /* Process direct roots in {gcroots,profiles}. */
+    using namespace nix::roots_tracer;
-    findRoots(stateDir + "/" + gcRootsDir, DT_UNKNOWN, roots);
-    findRoots(stateDir + "/profiles", DT_UNKNOWN, roots);
 
-    /* Add additional roots returned by different platforms-specific
+    const TracerConfig opts {
-       heuristics.  This is typically used to add running programs to
+      .storeDir = fs::path(storeDir),
-       the set of roots (to prevent them from being garbage collected). */
+      .stateDir = fs::path(stateDir.get())
-    findRuntimeRoots(roots, censor);
+    };
+    const std::set<fs::path> standardRoots = {
+        opts.stateDir / fs::path(gcRootsDir),
+        opts.stateDir / fs::path("gcroots"),
+    };
+    auto traceResult = traceStaticRoots(opts, standardRoots);
+    auto runtimeRoots = getRuntimeRoots(opts);
+    traceResult.storeRoots.insert(runtimeRoots.begin(), runtimeRoots.end());
+    for (auto & [rawRootInStore, externalRoots] : traceResult.storeRoots) {
+        if (!isInStore(rawRootInStore)) continue;
+        auto rootInStore = toStorePath(rawRootInStore).first;
+        if (!isValidPath(rootInStore)) continue;
+        std::unordered_set<std::string> primRoots;
+        for (const auto & externalRoot : externalRoots)
+            primRoots.insert(externalRoot.string());
+        roots.emplace(rootInStore, primRoots);
+    }
 }
 
 

src/libstore/local.mk

@@ -6,7 +6,7 @@ libstore_DIR := $(d)
 
 libstore_SOURCES := $(wildcard $(d)/*.cc $(d)/builtins/*.cc $(d)/build/*.cc)
 
-libstore_LIBS = libutil
+libstore_LIBS = libutil find-roots
 
 libstore_LDFLAGS += $(SQLITE3_LIBS) $(LIBCURL_LIBS) $(SODIUM_LIBS) -pthread
 ifdef HOST_LINUX
@@ -32,7 +32,7 @@ ifeq ($(HAVE_SECCOMP), 1)
 endif
 
 libstore_CXXFLAGS += \
- -I src/libutil -I src/libstore -I src/libstore/build \
+ -I src/libutil -I src/libstore -I src/libstore/build -I src/nix-find-roots/lib \
  -DNIX_PREFIX=\"$(prefix)\" \
  -DNIX_STORE_DIR=\"$(storedir)\" \
  -DNIX_DATA_DIR=\"$(datadir)\" \

src/nix-find-roots/lib/find-roots.hh

@@ -26,9 +26,9 @@ inline void logNone(std::string_view)
 { }
 
 struct TracerConfig {
-    fs::path storeDir = "/nix/store";
+    const fs::path storeDir = "/nix/store";
-    fs::path stateDir = "/nix/var/nix";
+    const fs::path stateDir = "/nix/var/nix";
-    fs::path socketPath = "/nix/var/nix/gc-socket/socket";
+    const fs::path socketPath = "/nix/var/nix/gc-socket/socket";
 
     std::function<void(std::string_view msg)> log = logNone;
     std::function<void(std::string_view msg)> debug = logNone;

src/nix-find-roots/main.cc

@@ -15,8 +15,12 @@ void logStderr(std::string_view msg)
 
 TracerConfig parseCmdLine(int argc, char** argv)
 {
-    TracerConfig res;
+    std::function<void(std::string_view msg)> log = logStderr;
-    res.log = logStderr;
+    std::function<void(std::string_view msg)> debug = logNone;
+    fs::path storeDir = "/nix/store";
+    fs::path stateDir = "/nix/var/nix";
+    fs::path socketPath = "/nix/var/nix/gc-trace-socket/socket";
+
     auto usage = [&]() {
         std::cerr << "Usage: " << string(argv[0]) << " [--verbose|-v] [-s storeDir] [-d stateDir] [-l socketPath]" << std::endl;
         exit(1);
@@ -40,23 +44,28 @@ TracerConfig parseCmdLine(int argc, char** argv)
                 usage();
                 break;
             case 'v':
-                res.debug = logStderr;
+                debug = logStderr;
                 break;
             case 's':
-                res.storeDir = fs::path(optarg);
+                storeDir = fs::path(optarg);
                 break;
             case 'd':
-                res.stateDir = fs::path(optarg);
+                stateDir = fs::path(optarg);
                 break;
             case 'l':
-                res.socketPath = fs::path(optarg);
+                socketPath = fs::path(optarg);
                 break;
             default:
                 std::cerr << "Got invalid char: " << (char)opt_char << std::endl;
                 abort();
         }
     };
-    return res;
+    return TracerConfig {
+        .storeDir = storeDir,
+        .stateDir = stateDir,
+        .socketPath = socketPath,
+        .debug = debug,
+    };
 }