From b88de416367d703eff36c87722537658f2aaee0f Mon Sep 17 00:00:00 2001 From: Ilya Biryukov Date: Thu, 10 Aug 2017 16:10:40 +0000 Subject: [PATCH] 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 --- clang/lib/Frontend/PrecompiledPreamble.cpp | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/clang/lib/Frontend/PrecompiledPreamble.cpp b/clang/lib/Frontend/PrecompiledPreamble.cpp index 15b24cbed484..cd7446189cc2 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 @@ llvm::ErrorOr 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()); }