gcc -o libname.so -shared -Wl,-z,defs,--retain-symbols-file,libname.exports,-L. libname.a -lc

gcc -o libname.so -shared -Wl,-z,defs,--retain-symbols-file,libname.exports,-L.,--whole-archive,libname.a,--no-whole-archive -lc

% cc -c -fPIC a.c
% nm a.o
00000000 T a
% ar rv liba.a a.o
ar: creating liba.a
a - a.o
% gcc -o liba.so -shared -u a liba.a
% nm liba.so | awk '$3 == "a" { print }'
0000042c T a

% g++ -c -fPIC a.c
% nm a.o | awk '$2 == "T" { print }'
00000000 T _Z1av