I am running these two commands, and I'm getting different output:
$ ldd `which ls`
linux-gate.so.1 => (0x00db3000)
libselinux.so.1 => /lib/i386-linux-gnu/libselinux.so.1 (0x00ba2000)
librt.so.1 => /lib/i386-linux-gnu/librt.so.1 (0x007bf000)
libacl.so.1 => /lib/i386-linux-gnu/libacl.so.1 (0x004ce000)
libc.so.6 => /lib/i386-linux-gnu/libc.so.6 (0x00110000)
libdl.so.2 => /lib/i386-linux-gnu/libdl.so.2 (0x00398000)
/lib/ld-linux.so.2 (0x00dea000)
libpthread.so.0 => /lib/i386-linux-gnu/libpthread.so.0 (0x00a83000)
libattr.so.1 => /lib/i386-linux-gnu/libattr.so.1 (0x00d3d000)
and then
objdump -x `which ls` | grep NEEDED
NEEDED libselinux.so.1
NEEDED librt.so.1
NEEDED libacl.so.1
NEEDED libc.so.6
What's up with that? I thought they both gave the library dependencies? The reason I care is that I suspect ldd
is the correct one, but I'm working on linux on ARM, where there is no ldd from what I can tell...
You can see the difference in the output.
objdump is simply dumping what the object itself lists as libraries containing unresolved symbols.
ldd is listing which libraries ld.so would actually load. And it follows the graph backward, so that you can see what would be loaded by those libraries. Which is how libpthread.so.0 winds up in the ldd output, despite not being in the objdump output.
So ldd is going to give a much, much better picture of what really needs to be available at runtime. But, when resolving compile/link-time problems, objdump is pretty helpful.