[ELF] Don't set the executable bit for relocatable or shared files

[phosek]

Summary

These are not executable files so they shouldn't be marked as such.

[ruiu]

So is true for .so, isn't it?

[phosek]

True, that's a good point.

[grimar]

+1 to testcase request.

ELF/Writer.cpp

1843

I believe LLD style avoids using ternary operator where possible.
So I see this code better as:

unsigned Flags = FileOutputBuffer::F_executable;
if (Config->Relocatable || Config->Shared)
  Flags = 0;

[ruiu]

ELF/Writer.cpp

1843

Yeah, sort of. I learned this style from Go. I'd prefer defaulting to 0 and re-setting F_executable though.

[phosek]

Test added.

[ruiu]

LGTM with this fix.

ELF/Writer.cpp

1842

Please remove !Config->Shared as other linkers set X bit to shared libraries.

ELF/Writer.cpp

 // Open a result file.
 template <class ELFT> void Writer<ELFT>::openFile() {
   if (!Config->Is64 && FileSize > UINT32_MAX) {
     error("output file too large: " + Twine(FileSize) + " bytes");
     return;
   }
 
   unlinkAsync(Config->OutputFile);
+  unsigned Flags = Config->Relocatable ? 0 : FileOutputBuffer::F_executable;
   Expected<std::unique_ptr<FileOutputBuffer>> BufferOrErr =
-      FileOutputBuffer::create(Config->OutputFile, FileSize,
-                               FileOutputBuffer::F_executable);
+      FileOutputBuffer::create(Config->OutputFile, FileSize, Flags);
 
   if (!BufferOrErr)
     error("failed to open " + Config->OutputFile + ": " +
           llvm::toString(BufferOrErr.takeError()));
   else
     Buffer = std::move(*BufferOrErr);
 }