Gcc
Creating a shared library is easy. First, create the object files that will go into the shared library using the gcc -fPIC or -fpic flag. The -fPIC and -fpic options enable ``position independent code generation, a requirement for shared libraries; see below for the differences. You pass the soname using the -Wl gcc option. The -Wl option passes options along to the linker (in this case the -soname linker option) - the commas after -Wl are not a typo, and you must not include unescaped whitespace in the option. Then create the shared library using this format:
gcc -shared -Wl,-soname,your_soname \
-o library_name file_list library_list
Here's an example, which creates two object files (a.o and b.o) and then creates a shared library that contains both of them. Note that this compilation includes debugging information (-g) and will generate warnings (-Wall), which aren't required for shared libraries but are recommended. The compilation generates object files (using -c), and includes the required -fPIC option:
gcc -fPIC -g -c -Wall a.c
gcc -fPIC -g -c -Wall b.c
gcc -shared -Wl,-soname,libmystuff.so.1 \
-o libmystuff.so.1.0.1 a.o b.o -lc
