Move macOS TMPDIR hack from initNix to initLibStore

This code is bad. We shouldn't unset variables in programs whose
children may need them. Fixing one issue at a time, so postponing.
See https://github.com/NixOS/nix/issues/7731

Part of an effort to make it easier to initialize the right things,
by moving code into the appropriate libraries.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
index 6848991a2..5a8825be5 100644
--- a/src/libstore/globals.cc
+++ b/src/libstore/globals.cc
@@ -343,6 +343,14 @@ void initLibStore() {
 
     preloadNSS();
 
+    /* On macOS, don't use the per-session TMPDIR (as set e.g. by
+       sshd). This breaks build users because they don't have access
+       to the TMPDIR, in particular in ‘nix-store --serve’. */
+#if __APPLE__
+    if (hasPrefix(getEnv("TMPDIR").value_or("/tmp"), "/var/folders/"))
+        unsetenv("TMPDIR");
+#endif
+
     initLibStoreDone = true;
 }