[LLVMdev] llvm-objdump

[Steve King]

Hi Kev,
I'm glad to hear llvm-objdump is getting attention.  I'm unclear on
how much output specialization one could (or should) do for ELF vs.
Mach-O.  If you're game, let's compare an example:

$ cat labeltest.s
.text
foo:
    nop
bar:
bum:
    nop
    jmp   bar
    jmp   bum
    jmp   baz
    nop
baz:
    nop

Assembling for x86 and llvm-objdump'ing, i get

$ llvm-mc -arch=x86 -filetype=obj labeltest.s -o x86_labeltest.o
$ llvm-objdump -d  x86_labeltest.o

x86_labeltest.o: file format ELF32-i386

Disassembly of section .text:
foo:
       0: 90                                           nop

bum:
       1: 90                                           nop
       2: eb fd                                         jmp -3
       4: eb fb                                         jmp -5
       6: eb 01                                         jmp 1
       8: 90                                           nop

baz:
       9: 90                                           nop

I get the dump above with or without -symbolize.

My personal golden reference, GNU objdump, does this:

$ objdump -dw x86_labeltest.o

x86_labeltest.o:     file format elf32-i386


Disassembly of section .text:

00000000 <foo>:
   0: 90                   nop

00000001 <bar>:
   1: 90                   nop
   2: eb fd                 jmp    1 <bar>
   4: eb fb                 jmp    1 <bar>
   6: eb 01                 jmp    9 <baz>
   8: 90                   nop

00000009 <baz>:
   9: 90                   nop

What does otool produce?


On Tue, Aug 26, 2014 at 11:16 AM, Kevin Enderby <enderby at apple.com> wrote:
> For branch targets my preference is to print the target’s address (not the displacement of the branch), and preferably in hex.

I like this too.

> I don’t think having multiple addresses for a target is a real problem with the exception of the address 0 (which is often an unrelocated no addend value).  So the trick is to not print the symbol name in the object with the address of zero in those cases

Right, relocations are a special case.