[lld-macho] Implement -fatal_warnings

[int3]

cc @gkm who implemented most of the option parsing

lld/MachO/Options.td

611

these groups are based on the groups used in the ld64 manpage. I think we should keep them, though I wouldn't object to defining a new group if you think it'd be more fitting

[thakis]

restore group

lld/MachO/Options.td

611

Oh, turns out this one can stay grp_rare, put it back. What confused me was that grp_undocumented causes warnings, so I had to remove grp_undocumented on -demangle in D91884. Which group should I use for that one?

[int3]

lld/MachO/Options.td

611

hmm I had a look at the current set of possible groups and none of them look like a great fit. However, grp_rare does seem to be a dumping ground for a variety of options that don't seem rare so much as miscellaneous. I guess we could put -demangle there too.

Another option would be to create a new group, e.g. grp_diagnostics, and put things like -fatal_warnings and -demangle there. I'm fine with either.

[thakis]

Thanks!

lld/MachO/Options.td

611

grp_rare kind of fits for -demangle, but clang passes it on literally every single lld invocation, so it isn't "rare" in the english meaning of that word. Not sure we care. If there's no explicit group, it shows up in the "OPTIONS" category, which is where old mach-o lld has it, which seems like a decent fit to me as well.

lld/MachO/DriverUtils.cpp

 opt::InputArgList MachOOptTable::parse(ArrayRef<const char *> argv) {
   // Make InputArgList from string vectors.
   unsigned missingIndex;
   unsigned missingCount;
   SmallVector<const char *, 256> vec(argv.data(), argv.data() + argv.size());
 
   opt::InputArgList args = ParseArgs(vec, missingIndex, missingCount);
 
+  // Handle -fatal_warnings early since it converts missing argument warnings
+  // to errors.
+  errorHandler().fatalWarnings = args.hasArg(OPT_fatal_warnings);
+
   if (missingCount)
     error(Twine(args.getArgString(missingIndex)) + ": missing argument");
 
   handleColorDiagnostics(args);
 
   for (opt::Arg *arg : args.filtered(OPT_UNKNOWN))
     error("unknown argument: " + arg->getSpelling());
   return args;

lld/MachO/Options.td

def application_extension : Flag<["-"], "application_extension">,
      HelpText<"Designate the linker output as safe for use in an application extension">,
      Flags<[HelpHidden]>,
      Group<grp_rare>;
 def no_application_extension : Flag<["-"], "no_application_extension">,
      HelpText<"Designate the linker output as unsafe for use in an application extension">,
      Flags<[HelpHidden]>,
      Group<grp_rare>;
 def fatal_warnings : Flag<["-"], "fatal_warnings">,
-     HelpText<"Escalate warnings as errors">,
-     Flags<[HelpHidden]>,
-     Group<grp_rare>;
+     HelpText<"Treat warnings as errors">;
 def no_eh_labels : Flag<["-"], "no_eh_labels">,
      HelpText<"In -r mode, suppress .eh labels in the __eh_frame section">,
      Flags<[HelpHidden]>,
      Group<grp_rare>;
 def warn_compact_unwind : Flag<["-"], "warn_compact_unwind">,
      HelpText<"Warn for each FDE that cannot compact into the __unwind_info section and must remain in the __eh_frame section">,
      Flags<[HelpHidden]>,
      Group<grp_rare>;

lld/test/MachO/fatal-warnings.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-apple-darwin %s -o %t1.o
+
+# RUN: %lld %t1.o -o /dev/null -single_module 2>&1 \
+# RUN:     | FileCheck -check-prefix=WARNING %s
+# RUN: not %lld %t1.o -fatal_warnings -o /dev/null -single_module 2>&1 \
+# RUN:     | FileCheck -check-prefix=ERROR %s
+
+# ERROR: error: Option `-single_module' is deprecated
+# WARNING: warning: Option `-single_module' is deprecated
+
+.globl _main
+_main: