How can I tell, with something like objdump, if an object file has been built with -fPIC?

Question

How can I tell, with something like objdump, if an object file has been built with -fPIC?

Answer 1

The answer depends on the platform. On most platforms, if output from

readelf --relocs foo.o | egrep '(GOT|PLT|JU?MP_SLOT)' 

is empty, then either foo.o was not compiled with -fPIC, or foo.o doesn't contain any code where -fPIC matters.

Answer 2

I just had to do this on a PowerPC target to find which shared object (.so) was being built without -fPIC. What I did was run readelf -d libMyLib1.so and look for TEXTREL. If you see TEXTREL, one or more source files that make up your .so were not built with -fPIC. You can substitute readelf with elfdump if necessary.

E.g.,

[user@host lib]$ readelf -d libMyLib1.so | grep TEXT   # Bad, not -fPIC  0x00000016 (TEXTREL) [user@host lib]$ readelf -d libMyLib2.so | grep TEXT   # Good, -fPIC [user@host lib]$ 

And to help people searching for solutions, the error I was getting when I ran my executable was this:

root@target:/# ./program: error while loading shared libraries: /usr/lib/libMyLi b1.so:  R_PPC_REL24 relocation at 0x0fc5987c for symbol 'memcpy' out of range 

I don't know whether this info applies to all architectures.

Source: blogs.oracle.com/rie