Question

I’ve got a shared library with some homemade functions, which I compile into my other programs, but I have to link the end program with all the libraries I have used to compile the static library. Here is an example:

I have function foo in the library which requires a function from another library libbar.so.

In my main program to use function foo I have to compile it with the -lbar flag. Is there a way I can compile my library statically so it includes all the required code from the other libraries, and I can compile my end program without needing the -lbar flag?

Answer 1

Shared objects (.so) aren’t libraries, they are objects. You can’t extract part of them and insert it in other libraries.

What you can do if build a shared object which references the other — but the other will be needed at run time. Just add the -lbar when linking libfoo.

If you are able to build libbar, you can obviously make a library which is the combination of libfoo and libbar. IIRC, you can also make the linker build a library which is libfoo and the needed part of libbar by linking a .a with the .o meant to go in libbar. Example:

gcc -fPIC -c lib1.c     # define foofn(), reference barfn1()
gcc -fPIC -c lib2a.c    # define barfn1(), reference barfn2()
gcc -fPIC -c lib2b.c    # define barfn2()
gcc -fPIC -c lib2c.c    # define barfn3()
gcc -c main.c           # reference foofn()
ar -cru libbar.a lib2*.o
gcc -shared -o libfoo.so lib1.o -L. -lbar
nm libfoo.so | grep barfn2()    # ok, not here
gcc -o prog main.o -L. -lfoo
env LD_LIBRARY_PATH=. ./prog    # works, so foofn(), barfn1() and barfn2() are found