after gmake size of library gets changes

Hello,
I have source code of c. When i compiled it using gmake my library gets created on AIX. But without changing the source code, if i try to do gmake each and every time then every time size of created library gets changed.
Can anyone tell me why it's happening?
Am i missing something in my Makefile?

What commands does gmake actually execute?

it doesn't execute any command.
It creates shared library. Size of that shared library is getting changed after every compilation with gmake without making the change in code.

Well, some commands are being executed if a shared library is created.

Can you share your Makefile with us?