Fixed a race condition in PrecompiledPreamble.
Summary:
Two PrecompiledPreambles, used in parallel on separate threads,
could be writing preamble to the same temporary file.
Reviewers: bkramer, krasimir, klimek
Reviewed By: klimek
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D36529
llvm-svn: 310618
diff --git a/clang/lib/Frontend/PrecompiledPreamble.cpp b/clang/lib/Frontend/PrecompiledPreamble.cpp
index 15b24cb..cd74461 100644
--- a/clang/lib/Frontend/PrecompiledPreamble.cpp
+++ b/clang/lib/Frontend/PrecompiledPreamble.cpp
@@ -28,6 +28,7 @@
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/MutexGuard.h"
+#include "llvm/Support/Process.h"
using namespace clang;
@@ -462,9 +463,16 @@
PrecompiledPreamble::TempPCHFile::createInSystemTempDir(const Twine &Prefix,
StringRef Suffix) {
llvm::SmallString<64> File;
- auto EC = llvm::sys::fs::createTemporaryFile(Prefix, Suffix, /*ref*/ File);
+ // Using a version of createTemporaryFile with a file descriptor guarantees
+ // that we would never get a race condition in a multi-threaded setting (i.e.,
+ // multiple threads getting the same temporary path).
+ int FD;
+ auto EC = llvm::sys::fs::createTemporaryFile(Prefix, Suffix, /*ref*/ FD,
+ /*ref*/ File);
if (EC)
return EC;
+ // We only needed to make sure the file exists, close the file right away.
+ llvm::sys::Process::SafelyCloseFileDescriptor(FD);
return TempPCHFile(std::move(File).str());
}