An objcopy equivalent for Mac / iPhone?

Question

I would like to rename symbols inside object files (.o) with something that would be the Mac equivalent of binutils' objcopy --redefine-syms tool.

I found no arm-apple-darwin10-objcopy. I tried the MacPorts' arm-elf-binutils port and also tried to play a bit with otool and segedit without much success.

Any ideas please?

Employment

Are you OK with defining aliases, which means that older symbols will still exists ? – Solecism

how about brew install binutils and gobjcopy? eg: gobjcopy --redefine-sym _D4main9foo_test1FZv=_foobar main.o main2.o; NOTE: the resulting executable seems wrong but nm main2.o | grep _foobar works – Blythebm

Answer 1

Sounds like a job for Agner Fog's objconv.

From the announcement:

I have now finished making full support for Mach-O files in the object file converter mentioned in my previous posts. You may use it as a replacement for the missing objcopy utility.

Objconv can be used for the following purposes:
Convert object files and library/archive files between Mach-O, ELF, COFF and OMF formats for all x86 and x86-64 platforms.

Change symbol names in object files, make symbols weak, add alias names to symbols.

Build, modify and convert static library files (*.a, *.lib) across platforms (Mac, Linux, BSD, Windows)

Dump object files and executable files

Disassemble object files and executable files. Very good disassembler.

• objconv manual

• objconv.zip - source

Lexis

from the FAQ: "11.3 Is it possible to convert files for ARM? No. A lot of people have asked about this, so there is obviously a need for such a tool, but I am not gonna make it. Objconv supports only files for x86 and x86-64 architectures. It will require a major rewrite of objconv to make a converter for ARM files." – Pangolin

Answer 2

I know I'm resurrecting this post from the dead, but...

I have a sudden need to do this as well, and discovering that objcopy doesn't work on OSX was a bit of a shock. But I think it's possible to use ld to achieve the same effect:

ld -r input.o -o output.o -alias oldsymbol newsymbol -unexported_symbol oldsymbol

This really just creates an alias for the symbol under a new name and hides the old one.

I haven't had a chance to do much testing yet, but looking at the output file with nm shows it seems to be doing the right thing.

Biagio

This command deletes all debug symbols. Do you know how to copy them from the original object file? – Chokedamp

objcopy can rename symbols T (text section symbol) and U (undefined) symbols. However, your ld solution can only handle the former. – Regicide

Answer 3

objconv does not currently work for ARM, so this option is not available for iPhone. It should be no problem to use objconv from elf to mach-o for mac osx x86/x64 though. Let me know if you found a solution for ARM

Blinker