For ASTUnit::Save, write the AST to a temporary and then rename it to the actual filename.
Should avoid race conditions. Addresses rdar://9788943.
llvm-svn: 135691
diff --git a/clang/lib/Frontend/ASTUnit.cpp b/clang/lib/Frontend/ASTUnit.cpp
index 89bc091..c50dea6 100644
--- a/clang/lib/Frontend/ASTUnit.cpp
+++ b/clang/lib/Frontend/ASTUnit.cpp
@@ -45,6 +45,7 @@
#include "llvm/Support/Path.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Timer.h"
+#include "llvm/Support/FileSystem.h"
#include "llvm/Support/CrashRecoveryContext.h"
#include <cstdlib>
#include <cstdio>
@@ -2304,18 +2305,39 @@
CXSaveError ASTUnit::Save(llvm::StringRef File) {
if (getDiagnostics().hasUnrecoverableErrorOccurred())
return CXSaveError_TranslationErrors;
-
+
+ // Write to a temporary file and later rename it to the actual file, to avoid
+ // possible race conditions.
+ llvm::sys::Path TempPath(File);
+ if (TempPath.makeUnique(/*reuse_current=*/false, /*ErrMsg*/0))
+ return CXSaveError_Unknown;
+ // makeUnique may or may not have created the file. Try deleting before
+ // opening so that we can use F_Excl for exclusive access.
+ TempPath.eraseFromDisk();
+
// FIXME: Can we somehow regenerate the stat cache here, or do we need to
// unconditionally create a stat cache when we parse the file?
std::string ErrorInfo;
- llvm::raw_fd_ostream Out(File.str().c_str(), ErrorInfo,
- llvm::raw_fd_ostream::F_Binary);
+ llvm::raw_fd_ostream Out(TempPath.c_str(), ErrorInfo,
+ llvm::raw_fd_ostream::F_Binary |
+ // if TempPath already exists, we should not try to
+ // overwrite it, we want to avoid race conditions.
+ llvm::raw_fd_ostream::F_Excl);
if (!ErrorInfo.empty() || Out.has_error())
return CXSaveError_Unknown;
serialize(Out);
Out.close();
- return Out.has_error()? CXSaveError_Unknown : CXSaveError_None;
+ if (Out.has_error())
+ return CXSaveError_Unknown;
+
+ if (llvm::error_code ec = llvm::sys::fs::rename(TempPath.str(), File)) {
+ bool exists;
+ llvm::sys::fs::remove(TempPath.str(), exists);
+ return CXSaveError_Unknown;
+ }
+
+ return CXSaveError_None;
}
bool ASTUnit::serialize(llvm::raw_ostream &OS) {