shared library constructor not working

Question

In my shared library I have to do certain initialization at the load time. If I define the function with the GCC attribute __attribute__ ((constructor)) it doesn\'t

Answer 1

From this link :

"Shared libraries must not be compiled with the gcc arguments -nostartfiles'' or-nostdlib''. If those arguments are used, the constructor/destructor routines will not be executed (unless special measures are taken)."

gcc/ld doesn't set the DT_INIT bit in the elf header when -nostdlib is used . You can check objdump -p and look for the section INIT in both cases. In attribute ((constructor)) case you wont find that INIT section . But for __init case you will find INIT section in the shared library.