Frontend: Default to creating output files using temporary files + rename.

- This is a more reliable default, as it behaves better on failure and also
   ensures that we create *new* files (instead of reusing existing inodes). This
   is useful for other applications (like lldb) which want to cache inode's to
   know when a file has been rewritten.

llvm-svn: 151961

clang/include/clang/Frontend/CompilerInstance.h

@@ -572,6 +572,10 @@ public:
   /// Create the default output file (from the invocation's options) and add it
   /// to the list of tracked output files.
   ///
+  /// The files created by this function always use temporary files to write to
+  /// their result (that is, the data is written to a temporary file which will
+  /// atomically replace the target output on success).
+  ///
   /// \return - Null on error.
   llvm::raw_fd_ostream *
   createDefaultOutputFile(bool Binary = true, StringRef BaseInput = "",

clang/lib/Frontend/CompilerInstance.cpp

@@ -470,7 +470,8 @@ CompilerInstance::createDefaultOutputFile(bool Binary,
                                           StringRef InFile,
                                           StringRef Extension) {
   return createOutputFile(getFrontendOpts().OutputFile, Binary,
-                          /*RemoveFileOnSignal=*/true, InFile, Extension);
+                          /*RemoveFileOnSignal=*/true, InFile, Extension,
+                          /*UseTemporary=*/true);
 }
 
 llvm::raw_fd_ostream *