[Bug c/53232] No warning for main() without a return statement with -std=c99

[vincent-gcc at vinc17 dot net]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53232

--- Comment #16 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> ---
(In reply to Jakub Jelinek from comment #15)
> But much more often it is intentional than unintentional.

That's the same thing for many kinds of warnings.