[SR-11541] Handle failure in the Driver's getTemporaryFilePath helper

[belkadan]

Previous ID	SR-11541
Radar	rdar://problem/55600413
Original Reporter	@belkadan
Type	Bug

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash, Driver
Assignee	None
Priority	Medium

md5: b1cf20b9e827a8612b37edfdaddd6d35

Issue Description:

const char *
ToolChain::JobContext::getTemporaryFilePath(const llvm::Twine &name,
                                            StringRef suffix) const {
  SmallString<128> buffer;
  std::error_code EC = llvm::sys::fs::createTemporaryFile(name, suffix, buffer);
  if (EC) {
    // FIXME: This should not take down the entire process.
    llvm::report_fatal_error("unable to create temporary file for filelist");
  }

  C.addTemporaryFile(buffer.str(), PreserveOnSignal::Yes);
  // We can't just reference the data in the TemporaryFiles vector because
  // that could theoretically get copied to a new address.
  return C.getArgs().MakeArgString(buffer.str());
}

This is obviously not optimal. The immediate action is to return an llvm::Expected<const char *> instead, to represent the failure, but all of the callers are constructing command-lines for the jobs to run for this compilation. That's not currently something that can fail.

[belkadan]

Forgot to mention: a possible failure reason is that TMPDIR is set to a non-existent or read-only directory.

[belkadan]

Compilation::getAllSourcesPath has a similar problem.

[belkadan]

And the writeAllSourcesFile helper, by contrast, is diagnosing and failing gracefully.

[belkadan]

Looks like some of the other places emitting diag::error_unable_to_make_temporary_file are not recovering gracefully, though.