Merge multiple .so shared libraries

Say I have a.so and b.so. Can I produce c.so as a single shared library with all the functions exported by a and b, of course resolving all intra-dependencies (i.e. all functions of b.so called by a.so and the other way around)?

I tried

gcc -shared -Wl,soname,c.so -o c.so a.so b.so

but it doesn't work.

Same goes if I archive a.o and b.o in a.a and b.a (which shouldn't modify a.o and b.o), and do

gcc -shared -Wl,soname,c.so -o c.so a.a b.a

Thanks