shared_library

Shared Library

We would like to create a shared link library containing the object code of the sum() and mul() functions written into mymath.c source file, which can be called from different C programs.

1. Compile Position Independent Code (PIC) mymath.o:

$ gcc -c -fPIC mymath.c

2. Create shared link library libmymath.so from mymath.o:

$ gcc -shared -o libmymath.so mymath.o

3. Generate the executable a.out using libmymath.so:

$ gcc main.c -L. -lmymath

or

$ gcc main.c libmymath.so

4. Now we must informing the dynamic linker that a shared library doesn't reside in the standard directories - /lib /usr/lib tipically. We can do that by setting the LD_LIBRARY_PATH environment variable:

LD_LIBRARY_PATH=./ ./a.out

or

$ export LD_LIBRARY_PATH=./

Now the executable is ready to be executed:

$ ./a.out

Naming conventions

library filename = lib + library name + .so + Major version + minor version + patch version

i.e.: libgnustep-base.so.1.25.1