ldd doesn't work on dynamically linked binary

Question

I have a binary that uses a bunch of .so files.

bash-3.00$ file foo
foo: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), for GNU/Linux 2.6.21, dynamically linked (uses shared libs), not stripped

But if I run ldd on this file, its not able to pick up the .so files the binary is dependent on.'

bash-3.00$ ldd foo
        not a dynamic executable
bash-3.00$

readelf does show the list of shared libraries used by the binary..

bash-3.00$ readelf -d  foo
Dynamic segment at offset 0x17c810 contains 70 entries:

  Tag        Type                         Name/Value
 0x00000001 (NEEDED)                     Shared library: [libdl.so.2]

Why is ldd not able to pick up the library dependencies in this case ?

Answer 1

Like one of the comment says - you tried using ldd on 64 bit system to inspect a 32-bit ELF object. ldd uses the standard dynamic linker to trace the dependencies, so if your platform doesn't have the linker required by the ELF object being inspected, ldd fails. Readelf and objdump are more robust in these situations.