Merge pull request #8517 from hercules-ci/fix-build-hook-error-for-lib-users

Fix build hook error for libstore library users

1 files changed, 24 insertions, 1 deletions

diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 32e9a6ea9..d53377239 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -77,7 +77,30 @@ Settings::Settings()
     allowedImpureHostPrefixes = tokenizeString<StringSet>("/System/Library /usr/lib /dev /bin/sh");
 #endif
 
-    buildHook = getSelfExe().value_or("nix") + " __build-remote";
+    /* Set the build hook location
+
+       For builds we perform a self-invocation, so Nix has to be self-aware.
+       That is, it has to know where it is installed. We don't think it's sentient.
+
+       Normally, nix is installed according to `nixBinDir`, which is set at compile time,
+       but can be overridden. This makes for a great default that works even if this
+       code is linked as a library into some other program whose main is not aware
+       that it might need to be a build remote hook.
+
+       However, it may not have been installed at all. For example, if it's a static build,
+       there's a good chance that it has been moved out of its installation directory.
+       That makes `nixBinDir` useless. Instead, we'll query the OS for the path to the
+       current executable, using `getSelfExe()`.
+
+       As a last resort, we resort to `PATH`. Hopefully we find a `nix` there that's compatible.
+       If you're porting Nix to a new platform, that might be good enough for a while, but
+       you'll want to improve `getSelfExe()` to work on your platform.
+     */
+    std::string nixExePath = nixBinDir + "/nix";
+    if (!pathExists(nixExePath)) {
+        nixExePath = getSelfExe().value_or("nix");
+    }
+    buildHook = nixExePath + " __build-remote";
 }
 
 void loadConfFile()