[LTO] Add error message on IO error in compileOptimizedToFile.

[efriedma]

Summary

(No testcase because it's difficult to force an error here.)

[davide]

This seems reasonable. We do something similar in other places (and unfortunately is very hard to test in isolation).

[mehdi_amini]

LGTM. Thanks.

lib/LTO/LTOCodeGenerator.cpp

261

Can you get the + Filename on the same line as the initialization for ErrMsg?
(Otherwise never mind).

[mehdi_amini]

Just wondering: can't you get an error by providing an output path in a non-existing directory?

[efriedma]

lib/LTO/LTOCodeGenerator.cpp

261

I guess I could write std::string ErrMsg = Twine("could not write object file: ") + Filename;. Is that better?

[davide]

lib/LTO/LTOCodeGenerator.cpp

261

I would rather leave it as is.

[efriedma]

If file creation fails, you hit a different error path. This is the error path you hit if the disk runs out of space or something like that.

[mehdi_amini]

lib/LTO/LTOCodeGenerator.cpp

261

I'd write: std::string ErrMsg = "could not write object file: " + Filename.str(); (if it compiles)

[davide]

lib/LTO/LTOCodeGenerator.cpp

261

Agree, if it compiles. But using the Twine is a little bit cumbersome here, at least to me.

lib/LTO/LTOCodeGenerator.cpp

bool LTOCodeGenerator::compileOptimizedToFile(const char **Name) {
   }
 
   // generate object file
   tool_output_file objFile(Filename, FD);
 
   bool genResult = compileOptimized(&objFile.os());
   objFile.os().close();
   if (objFile.os().has_error()) {
+    std::string ErrMsg = "could not write object file: ";
+    ErrMsg += Filename;
+    emitError(ErrMsg);
     objFile.os().clear_error();
     sys::fs::remove(Twine(Filename));
     return false;
   }
 
   objFile.keep();
   if (!genResult) {
     sys::fs::remove(Twine(Filename));