[llvm-nm] Don't error out on multiple occurrances of the -g/--external-only flag

[mstorsjo]

Summary

GNU binutils nm doesn't error out on this, and some projects' build systems can end up doing that in some cases. Allowing that seems like a better target than trying to avoid user projects passing multiple -g parameters to $NM.

[smeenai]

I'm not super familiar with the option parser by any means, but I think changing specific flags to be ZeroOrMore rather than Optional is much better than doing a global change for the behavior of Optional.

[zturner]

Agreed. Optional should basically be called OneOrZero. And if you think about it in those terms, it obviously doesn't make sense to allow it to be specified more than once.

Just change this specific option to be ZeroOrMore

[mstorsjo]

In D39539#914121, @zturner wrote:

Agreed. Optional should basically be called OneOrZero. And if you think about it in those terms, it obviously doesn't make sense to allow it to be specified more than once.

Just change this specific option to be ZeroOrMore

Right - I hadn't realized how one could change that in cl::opt - now I see.

[mstorsjo]

Changed the type of this option instead.

[ruiu]

LGTM

test/tools/llvm-nm/X86/externalonly.test

 # RUN: llvm-nm -g %p/Inputs/hello.obj.macho-x86_64 | FileCheck %s
+# RUN: llvm-nm -g -g %p/Inputs/hello.obj.macho-x86_64 | FileCheck %s
 
 # CHECK-NOT: EH_frame0
 # CHECK: _main

tools/llvm-nm/llvm-nm.cpp

cl::alias DynamicSyms2("D", cl::desc("Alias for --dynamic"),
                        cl::aliasopt(DynamicSyms), cl::Grouping);
 
 cl::opt<bool> DefinedOnly("defined-only",
                           cl::desc("Show only defined symbols"));
 cl::alias DefinedOnly2("U", cl::desc("Alias for --defined-only"),
                        cl::aliasopt(DefinedOnly), cl::Grouping);
 
 cl::opt<bool> ExternalOnly("extern-only",
-                           cl::desc("Show only external symbols"));
+                           cl::desc("Show only external symbols"),
+                           cl::ZeroOrMore);
 cl::alias ExternalOnly2("g", cl::desc("Alias for --extern-only"),
-                        cl::aliasopt(ExternalOnly), cl::Grouping);
+                        cl::aliasopt(ExternalOnly), cl::Grouping,
+                        cl::ZeroOrMore);
 
 cl::opt<bool> BSDFormat("B", cl::desc("Alias for --format=bsd"),
                         cl::Grouping);
 cl::opt<bool> POSIXFormat("P", cl::desc("Alias for --format=posix"),
                           cl::Grouping);
 cl::opt<bool> DarwinFormat("m", cl::desc("Alias for --format=darwin"),
                            cl::Grouping);