[LLVMbugs] [Bug 13613] New: llvm-nm prints incorrect symbol types on Mac

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Wed Aug 15 07:22:18 PDT 2012


             Bug #: 13613
           Summary: llvm-nm prints incorrect symbol types on Mac
           Product: tools
           Version: trunk
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: llvm-nm
        AssignedTo: unassignedbugs at nondot.org
        ReportedBy: samsonov at google.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

llvm-nm seems to be broken for mach-o binaries:
$ cat main.cc
extern "C" {
void f1() {}
void f2() {}
}  // extern "C"

int main() {
  return 0;
$ clang++ main.cc
$ nm a.out 
0000000100001040 S _NXArgc
0000000100001048 S _NXArgv
0000000100001058 S ___progname
0000000100000000 T __mh_execute_header
0000000100001050 S _environ
                 U _exit
0000000100000ec0 T _f1
0000000100000ef0 T _f2
0000000100000ed0 T _main
0000000100001000 s _pvars
                 U dyld_stub_binder
0000000100000e80 T start
$ llvm-nm a.out
100001040 s _NXArgc
100001048 s _NXArgv
100001058 s ___progname
100000000 S __mh_execute_header
100001050 s _environ
00000000 u _exit
100000ec0 s _f1
100000ed0 s _main
100001000 s _pvars
00000000 u dyld_stub_binder
100000e80 s start

1. Notice that symbol _f2 is just gone - I've checked that it somewhy has
SF_FormatSpecific flag and is excluded in the following statement in
297     if (!DebugSyms && (symflags & SymbolRef::SF_FormatSpecific))
298       continue;
That looks weird.

2. Symbol types look completely strange and different from what usual nm
lib/Object/MachOObjectFile.cpp indeed returns only "u" or "s" as a symbol type
(see MachOObjectFile::getSymbolNMTypeChar), while, for example,
include/llvm/Object/ELF.h has completely different logic (and thus llvm-nm
works much better and more like usual "nm" on Linux).

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