https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591
--- Comment #3 from Kjetil Matheussen <k.s.matheussen at notam02 dot no> --- I didn't know about this gnu extension. But regardless, shouldn't gcc complain when the proto doesn't match the function itself? Also, although I don't understand how this extension works from the documentation, I have a feeling that there should have been a warning or error when compiling code calling "afunction" as well? int main(){ return afunction(5, NULL); } (this compiles just fine)