[llvm-dwp] Use buffer_stream if output file is not seekable (e.g. "-")

[MaskRay]

Remove comment

[dblaikie]

tools/llvm-dwp/llvm-dwp.cpp

707

Could use Optional<buffer_ostream> here to save an extra allocation?

[MaskRay]

std::unique_ptr -> Optional to save an extra allocation

[mkazantsev]

Hi,

This commit has caused massive buildbot failures on compilation, see for example http://lab.llvm.org:8011/builders/clang-cmake-x86_64-avx2-linux/builds/5953/steps/build%20stage%201/logs/stdio

I have reverted it as https://reviews.llvm.org/rL341515 to make buildbot green again.

• Max

[MaskRay]

In D51707#1225541, @mkazantsev wrote:

Hi,

This commit has caused massive buildbot failures on compilation, see for example http://lab.llvm.org:8011/builders/clang-cmake-x86_64-avx2-linux/builds/5953/steps/build%20stage%201/logs/stdio

I have reverted it as https://reviews.llvm.org/rL341515 to make buildbot green again.

• Max

Thanks! It was because of existing using namespace cl; in the file. I have changed it to use explicit cl:: qualified names and re-landed the commit

test/tools/llvm-dwp/X86/merge.test

-RUN: llvm-dwp %p/../Inputs/merge/notypes/c.dwo %p/../Inputs/merge/notypes/ab.dwp -o %t
-RUN: llvm-dwarfdump -v %t | FileCheck --check-prefix=CHECK --check-prefix=NOTYP %s
+RUN: llvm-dwp %p/../Inputs/merge/notypes/c.dwo %p/../Inputs/merge/notypes/ab.dwp -o - | \
+RUN:   llvm-dwarfdump -v - | FileCheck --check-prefix=CHECK --check-prefix=NOTYP %s
 
 FIXME: For some reason, piping straight from llvm-dwp to llvm-dwarfdump -v doesn't behave well - looks like dwarfdump is reading/closes before dwp has finished.
 
 DWP from a DWO (c.dwo) and a DWP (ab.dwp, created from a.dwo and b.dwo)
 Make sure the entries for A and B are updated correctly when read/processed from ab.dwp
 a.cpp:
   struct foo { };
   foo a;

tools/llvm-dwp/llvm-dwp.cpp

int main(int argc, char **argv) {
 
   MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
   if (!MCE)
     return error("no code emitter for target " + TripleName, Context);
 
   // Create the output file.
   std::error_code EC;
   raw_fd_ostream OutFile(OutputFilename, EC, sys::fs::F_None);
+  std::unique_ptr<buffer_ostream> BOS;
+  raw_pwrite_stream *OS;
   if (EC)
     return error(Twine(OutputFilename) + ": " + EC.message(), Context);
+  if (OutFile.supportsSeeking()) {
+    OS = &OutFile;
+  } else {
+    BOS = make_unique<buffer_ostream>(OutFile);
+    OS = BOS.get();
+  }
 
   MCTargetOptions MCOptions = InitMCTargetOptionsFromFlags();
   std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
       TheTriple, MC, std::unique_ptr<MCAsmBackend>(MAB),
-      MAB->createObjectWriter(OutFile), std::unique_ptr<MCCodeEmitter>(MCE),
+      MAB->createObjectWriter(*OS), std::unique_ptr<MCCodeEmitter>(MCE),
       *MSTI, MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
       /*DWARFMustBeAtTheEnd*/ false));
   if (!MS)
     return error("no object streamer for target " + TripleName, Context);
 
   std::vector<std::string> DWOFilenames = InputFiles;
   for (const auto &ExecFilename : ExecFilenames) {
     auto DWOs = getDWOFilenames(ExecFilename);