Use "foo-12345.o" instead of "foo.o-12345" as temporary file name.

[thakis]

Summary

This helps some tools that do things based on the output's extension.

For example, we got reports from users on Windows that have a tool that scan a build output dir (but skip .obj files). The tool would keep the "foo.obj-12345" file open, and then when clang tried to rename the temp file to the final output filename, that would fail. By making the tempfile end in ".obj", tools like this will now skip the temp files as well.

[rnk]

Looks good, but let's confirm with Richard before we change behavior.

[mcrosier]

Seems reasonable to me as well..

[rnk]

I discovered this code in llvm/lib/Support/Windows/Signals.inc which explains why we leak so many temp files on Windows:

// FIXME: open files cannot be deleted.
if (FilesToRemove != NULL)
  while (!FilesToRemove->empty()) {
    llvm::sys::fs::remove(FilesToRemove->back());
    FilesToRemove->pop_back();
  }

Output files are pretty much always open, so that FIXME is kind of a joke. The code basically doesn't work at all on Windows. =(

[thakis]

I'm going to land this. It's early in the 6.0 cycle, so if this causes issues, we should have time to find them and then follow up in case we run into any.

[thakis]

309984.

[chapuni]

Excuse me, I have reverted this in rL310030 to unbreak -fmodules.

See GlobalModuleIndex.cpp. It seeks the suffix ".pcm".

[thakis]

Hm, that's unfortunate. I don't see a good way to rescue this patch.

We could keep the lhs of this and always append ".tmp", then tools at least had a way of filtering out the temp files. Hm.

[thakis]

We went with https://reviews.llvm.org/D36413 instead. (Upstream issue was https://crbug.com/751225)

lib/Frontend/CompilerInstance.cpp

else {
         if (!llvm::sys::fs::is_regular_file(Status))
           UseTemporary = false;
       }
     }
   }
 
   if (UseTemporary) {
     // Create a temporary file.
-    SmallString<128> TempPath;
-    TempPath = OutFile;
+    // Insert -%%%%%%%% before the extension (if any), so that tools doing
+    // things based on the file extension do the right thing.
+    StringRef OutputExtension = llvm::sys::path::extension(OutFile);
+    SmallString<128> TempPath =
+        StringRef(OutFile).drop_back(OutputExtension.size());
     TempPath += "-%%%%%%%%";
+    TempPath += OutputExtension;
     int fd;
     std::error_code EC =
         llvm::sys::fs::createUniqueFile(TempPath, fd, TempPath);
 
     if (CreateMissingDirectories &&
         EC == llvm::errc::no_such_file_or_directory) {
       StringRef Parent = llvm::sys::path::parent_path(OutputPath);
       EC = llvm::sys::fs::create_directories(Parent);