How do I create .so files with all libraries statically linked into it?

Question

I want to create a .so file with all libraries (GMP and PROTOBUF) statically linked into it so that it can be used in other systems without installing those libraries.

This is what I did for MAC:

gcc -I /usr/local/include -shared -o xyz.so -g xyz.c /usr/local/lib/libprotobuf-c.a /usr/local/lib/libgmp.a

But it doesn't work for Linux. How can I make it work for Linux?

Answer 1

A shared library should (on Linux) practically contain position-independent code (PIC). So the correct way to build a shared library libxyz.so out of a single source file xyz.c is

gcc -Wall -g -shared -I/usr/local/include -o libxyz.so -fPIC xyz.c

(and you could -and probably want to- add rpath related options)

A static library don't contain PIC (unless it was specially built as such, which is very uncommon on Linux ; on Debian the only example I know is the special libc6-pic package provided to facilitate build of customized and extended libc*so ).

You need to link PIC variants of these libraries; so you should build them from their source code.

Read Drepper's How To Write Shared Libraries for more, and also Program Library HowTo .

^{(In some few theoretical weird cases, you could link a shared library which don't contain PIC, but that will make their dynamic linking extremely slow, since a lot of relocations would be processed and their code segment won't be shared -between several processes- by appropriate calls to mmap(2) done by ld-linux(8) ; this is not recommended at all, is very brittle, and often won't work well; I never did that)}

I want to create a .so file with all libraries (GMP and PROTOBUF) statically linked into it

Don't do that . I explained why. And doing that is against the (social) rules on Linux (because your users don't want to have zillions of variants of libgmp, etc...).

You can however link a shared library with some previous other (more basic) shared libraries. In your case, I recommend doing that. So require your user to have installed GMP and PROTOBUF packages.

Consider also providing packages for your (or common) Linux distributions (eg a .deb file for Ubuntu or Debian)

Alternatively, publish your library code as free software ; you might then hope that several users would download its source, and perhaps (eventually) some distribution would package it. You could wait years for that to happen; or at least you get help to package it.