Libc symbols not found

When i patch an elf with a different libc-*.so and gdb it i keep get:
Can not get libc version
Cannot get main_arena's symbol address. Make sure you install libc debug file (libc6-dbg & libc6-dbg:i386 for debian package).
can't find heap info
Already installed libc6-dbg and libc6-dbg:i386
What should i do?