From 9cca68dbfc42f7778f8db0bcfe8b3e575599ac0f Mon Sep 17 00:00:00 2001 From: Argyrios Kyrtzidis Date: Thu, 21 Jul 2011 18:44:49 +0000 Subject: [PATCH] For ASTUnit::Save, write the AST to a temporary and then rename it to the actual filename. Should avoid race conditions. Addresses rdar://9788943. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135691 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Frontend/ASTUnit.cpp | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp index 89bc0919e5..c50dea6aa3 100644 --- a/lib/Frontend/ASTUnit.cpp +++ b/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 #include @@ -2304,18 +2305,39 @@ void ASTUnit::CodeComplete(llvm::StringRef File, unsigned Line, unsigned Column, 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) { -- 2.50.1