Frontend: Respect -working-directory when checking if output files can be written

[dexonsmith]

Summary

Call FixupRelativePath when opening output files to ensure that
-working-directory is used when checking up front for write failures,
not just when finalizing the files at the end. This also moves the
temporary file into the same directory as the output file.

[dexonsmith]

ping / rebase

[steven_wu]

LGTM. I will commit this if no objection.

[steven_wu]

Actually, we need to fix the case when output is '-'.

[steven_wu]

Rebase patch and fix the problem when the input is '-'

clang/lib/Frontend/CompilerInstance.cpp

for (OutputFile &OF : OutputFiles) {
     if (!OF.File)
       continue;
 
     if (OF.File->TmpName.empty()) {
       consumeError(OF.File->discard());
       continue;
     }
 
-    // If '-working-directory' was passed, the output filename should be
-    // relative to that.
-    SmallString<128> NewOutFile(OF.Filename);
-    FileMgr->FixupRelativePath(NewOutFile);
-
-    llvm::Error E = OF.File->keep(NewOutFile);
+    llvm::Error E = OF.File->keep(OF.Filename);
     if (!E)
       continue;
 
     getDiagnostics().Report(diag::err_unable_to_rename_temp)
         << OF.File->TmpName << OF.Filename << std::move(E);
 
     llvm::sys::fs::remove(OF.File->TmpName);
   }

 Expected<std::unique_ptr<llvm::raw_pwrite_stream>>
 CompilerInstance::createOutputFileImpl(StringRef OutputPath, bool Binary,
                                        bool RemoveFileOnSignal,
                                        bool UseTemporary,
                                        bool CreateMissingDirectories) {
   assert((!CreateMissingDirectories || UseTemporary) &&
          "CreateMissingDirectories is only allowed when using temporary files");
 
+  // If '-working-directory' was passed, the output filename should be
+  // relative to that.
+  Optional<SmallString<128>> AbsPath;
+  if (OutputPath != "-" && !llvm::sys::path::is_absolute(OutputPath)) {
+    AbsPath.emplace(OutputPath);
+    FileMgr->FixupRelativePath(*AbsPath);
+    OutputPath = *AbsPath;
+  }
+
   std::unique_ptr<llvm::raw_fd_ostream> OS;
   Optional<StringRef> OSFile;
 
   if (UseTemporary) {
     if (OutputPath == "-")
       UseTemporary = false;
     else {
       llvm::sys::fs::file_status Status;

clang/test/Frontend/output-paths.c

 // RUN: not %clang_cc1 -emit-llvm -o %t.doesnotexist/somename %s 2> %t
 // RUN: FileCheck -check-prefix=OUTPUTFAIL -DMSG=%errc_ENOENT -input-file=%t %s
 
 // OUTPUTFAIL: error: unable to open output file '{{.*}}doesnotexist{{.}}somename': '[[MSG]]'
+
+// Check that -working-directory is respected when diagnosing output failures.
+//
+// RUN: rm -rf %t.d && mkdir -p %t.d/%basename_t-inner.d
+// RUN: %clang_cc1 -emit-llvm -working-directory %t.d -E -o %basename_t-inner.d/somename %s -verify
+// expected-no-diagnostics
+
+// RUN: %clang_cc1 -working-directory %t.d -E %s -o - | FileCheck %s
+// CHECK: # 1