[readobj] Improve the messages output by unsupported options when using --elf-output-style=GNU

[kazuminn]

Summary

I'm bigginer for good first issue.

implemented: Improve the messages output by unsupported options when using --elf-output-style=GNU on llvm-readobj

github url:
https://github.com/llvm/llvm-project/issues/51294

Of course, I built it and tested it manually.
I don't have commit rights, so when merge, do it for someone else.

I couldn't find the readobj code owner from CODE_OWNER.txt, so I've nominated someone close.
Let me know if you have a more appropriate review.

Thanks.

[kazuminn]

sorry.
working progress.

[jhenderson]

Hi @kazuminn,

When preparing your diff for upload to phabricator, please make sure to include full diff context, something like -U999999 in the command that generates the diff would do well for that. This allows us to search around the code a bit more.

I'm happy to review this, but for future reference, you should look in the Github history of the file for recent committers and those who reviewed their work to find good candidates for review.

Thank you for taking a look at this, but I'm not sure you've got the right idea with this piece of work though. For ease of reference, here is the github issues content from the link you posted:

A number of options supported by --elf-output-style=LLVM are not implemented for GNU output style, a message is output in these cases which is not too useful for the user. For example use of --elf-linker-options prints:

"printELFLinkerOptions not implemented!"

This is the name of the function. A description of the command line option or missing functionality would be clearer.

Other examples are seen in printCGProfile() and printBBAddrMaps().

To explain further what we would like to see: at the moment, if you specify a command-line like llvm-readobj --elf-output-style=GNU some-file.o --elf-linker-options, you get an output as described in the quote above. To improve this, all you need to do really is replace the output with something more descriptive of the user interface, for example "--elf-linker-options not supported for GNU output style". You should then do the same for other options that are similar - look through the ElfDumper.cpp code for such examples, which should be fairly easy to spot. https://github.com/llvm/llvm-project/blob/626039cdcc16b429c4403d36fad13fba2a6c14e9/llvm/tools/llvm-readobj/ELFDumper.cpp#L5762 is the location for the --elf-linker-options option discussed directly in the issue.

Rather than printing directly to the standard output stream, it might make more sense to change these messages to warnings. Look for instances of reportUniqueWarning for how to use it.

Finally, you should then add a test file under llvm/test/tools/llvm-readobj/ELF which shows that the unimplemented messages are printed as expected. There are plenty of good examples of testing warning messages in the other test files in that directory for you to use as a basis. Feel free to ask for help if you get stuck though.

llvm/tools/llvm-readobj/ELFDumper.cpp

   void printHashHistograms() override;
   void printCGProfile() override;
   void printBBAddrMaps() override;
+  void printELFOutputStyle() override;
   void printAddrsig() override;
   void printNotes() override;
   void printELFLinkerOptions() override;

   OS << "GNUStyle::printBBAddrMaps not implemented\n";
 }
 
+template <class ELFT> void GNUELFDumper<ELFT>::printELFOutputStyle() {
+  OS << "GNUStyle::printELFOutputStyle not implemented\n";
+}
+
 static Expected<std::vector<uint64_t>> toULEB128Array(ArrayRef<uint8_t> Data) {
   std::vector<uint64_t> Ret;
   const uint8_t *Cur = Data.begin();

llvm/tools/llvm-readobj/ObjDumper.h

   virtual void printHashHistograms() {}
   virtual void printCGProfile() {}
   virtual void printBBAddrMaps() {}
+  virtual void printELFOutputStyle() {}
   virtual void printAddrsig() {}
   virtual void printNotes() {}
   virtual void printELFLinkerOptions() {}

llvm/tools/llvm-readobj/llvm-readobj.cpp

       Dumper->printSectionDetails();
     else
       Dumper->printSectionHeaders();
+  } else if (opts::Output == opts::GNU) {
+    Dumper->printELFOutputStyle();
   }
 
   if (opts::HashSymbols)