* nix-store, nix-instantiate: added an option `--add-root' to

  immediately add the result as a permanent GC root.  This is the only
  way to prevent a race with the garbage collector.  For instance, the
  old style

    ln -s $(nix-store -r $(nix-instantiate foo.nix)) \
      /nix/var/nix/gcroots/result

  has two time windows in which the garbage collector can interfere
  (by GC'ing the derivation and the output, respectively).  On the
  other hand,

    nix-store --add-root /nix/var/nix/gcroots/result -r \
      $(nix-instantiate --add-root /nix/var/nix/gcroots/drv \
        foo.nix)

  is safe.

* nix-build: use `--add-root' to prevent GC races.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libstore/store.cc b/src/libstore/store.cc
index c7b84e7c6..b915fce24 100644
--- a/src/libstore/store.cc
+++ b/src/libstore/store.cc
@@ -168,7 +168,7 @@ void copyPath(const Path & src, const Path & dst)
 }
 
 
-static bool isInStore(const Path & path)
+bool isStorePath(const Path & path)
 {
     return path[0] == '/'
         && path.compare(0, nixStore.size(), nixStore) == 0
@@ -180,7 +180,7 @@ static bool isInStore(const Path & path)
 
 void assertStorePath(const Path & path)
 {
-    if (!isInStore(path))
+    if (!isStorePath(path))
         throw Error(format("path `%1%' is not in the Nix store") % path);
 }
 
@@ -579,7 +579,7 @@ void verifyStore()
         if (!pathExists(path)) {
             printMsg(lvlError, format("path `%1%' disappeared") % path);
             invalidatePath(path, txn);
-        } else if (!isInStore(path)) {
+        } else if (!isStorePath(path)) {
             printMsg(lvlError, format("path `%1%' is not in the Nix store") % path);
             invalidatePath(path, txn);
         } else