flushing stdout of c executable

I've got program that crashes after several printing command lines. however, I cannot see the output even though those prints already performed. this lead me to the assumption that there's a buffer that dump output after accumulating enough data, and if program crashed unexpectedly, the buffer disappear.

For debugging my crash, I'd like to set this buffer to zero and avoid performance degradation, so i can see the prints prior to the crash event.

thanks

via Chebli Mohamed