Store newly spliced executables as copies.

During multithreaded splicing, the main process can be forked (inheriting open file descriptors). In this case, the executable file saved using hardlinking becomes inaccessible. To prevent this, executables must be stored as copies made in a child process.

1 files changed, 10 insertions, 2 deletions

diff --git a/src/buildtool/storage/local_cas.tpp b/src/buildtool/storage/local_cas.tpp
index e0cb3883..97ecf1a3 100644
--- a/src/buildtool/storage/local_cas.tpp
+++ b/src/buildtool/storage/local_cas.tpp
@@ -78,8 +78,16 @@ requires(kIsLocalGeneration) auto LocalCAS<kDoGlobalUplink>::LocalUplinkBlob(
     }
 
     // Uplink blob from older generation to the latest generation.
-    return blob_path_latest.has_value() or
-           latest.StoreBlob</*kOwner=*/true>(*blob_path, is_executable);
+    if (spliced and is_executable) {
+        // During multithreaded splicing, the main process can be forked
+        // (inheriting open file descriptors). In this case, an executable file
+        // saved using hardlinking becomes inaccessible. To prevent this,
+        // executables must be stored as copies made in a child process.
+        return latest.StoreBlob</*kOwner=*/false>(*blob_path, is_executable)
+            .has_value();
+    }
+    return latest.StoreBlob</*kOwner=*/true>(*blob_path, is_executable)
+        .has_value();
 }
 
 template <bool kDoGlobalUplink>