[Support] [Windows] Use RemoveFileOnSignal if unable to use the delete-on-close flag

[mstorsjo]

Summary

This takes care of cleaning up the temp files on crashes. It doesn't
handle cleanup when explicitly killed though.

I left this out from D111875 because I was worried it would end up too
messy and didn't want to hold up the rest of it on it, but it turns out
it should be pretty straightforward.

[mstorsjo]

@akhuang - Does this seem sensible to you?

[akhuang]

lgtm!

llvm/lib/Support/Path.cpp

#ifdef _WIN32
   bool Remove = RemoveOnClose;
 #else
   // Always try to remove the file.
   bool Remove = true;
 #endif
   std::error_code RemoveEC;
   if (Remove && !TmpName.empty()) {
     RemoveEC = fs::remove(TmpName);
-#ifndef _WIN32
     sys::DontRemoveFileOnSignal(TmpName);
-#endif
     if (!RemoveEC)
       TmpName = "";
   } else {
     TmpName = "";
   }
   return errorCodeToError(RemoveEC);
 }
 
#else
   std::error_code RenameEC = fs::rename(TmpName, Name);
   if (RenameEC) {
     // If we can't rename, try to copy to work around cross-device link issues.
     RenameEC = sys::fs::copy_file(TmpName, Name);
     // If we can't rename or copy, discard the temporary file.
     if (RenameEC)
       remove(TmpName);
   }
-  sys::DontRemoveFileOnSignal(TmpName);
 #endif
+  sys::DontRemoveFileOnSignal(TmpName);
 
   if (!RenameEC)
     TmpName = "";
 
   if (close(FD) == -1) {
     std::error_code EC(errno, std::generic_category());
     return errorCodeToError(EC);
   }
   FD = -1;
 
   return errorCodeToError(RenameEC);
 }
 
 Error TempFile::keep() {
   assert(!Done);
   Done = true;
 
 #ifdef _WIN32
   auto H = reinterpret_cast<HANDLE>(_get_osfhandle(FD));
   if (std::error_code EC = setDeleteDisposition(H, false))
     return errorCodeToError(EC);
-#else
-  sys::DontRemoveFileOnSignal(TmpName);
 #endif
+  sys::DontRemoveFileOnSignal(TmpName);
 
   TmpName = "";
 
   if (close(FD) == -1) {
     std::error_code EC(errno, std::generic_category());
     return errorCodeToError(EC);
   }
   FD = -1;
 
   return Error::success();
 }
 
 Expected<TempFile> TempFile::create(const Twine &Model, unsigned Mode,
                                     OpenFlags ExtraFlags) {
   int FD;
   SmallString<128> ResultPath;
   if (std::error_code EC =
           createUniqueFile(Model, FD, ResultPath, OF_Delete | ExtraFlags, Mode))
     return errorCodeToError(EC);
 
   TempFile Ret(ResultPath, FD);
 #ifdef _WIN32
   auto H = reinterpret_cast<HANDLE>(_get_osfhandle(FD));
+  bool SetSignalHandler = false;
   if (std::error_code EC = setDeleteDisposition(H, true)) {
     Ret.RemoveOnClose = true;
+    SetSignalHandler = true;
   }
 #else
-  if (sys::RemoveFileOnSignal(ResultPath)) {
+  bool SetSignalHandler = true;
+#endif
+  if (SetSignalHandler && sys::RemoveFileOnSignal(ResultPath)) {
     // Make sure we delete the file when RemoveFileOnSignal fails.
     consumeError(Ret.discard());
     std::error_code EC(errc::operation_not_permitted);
     return errorCodeToError(EC);
   }
-#endif
   return std::move(Ret);
 }
 } // namespace fs
 
 } // namespace sys
 } // namespace llvm