Isn't this supposed to be caught by this check:
quoted
quoted
a, __same_type(a, NULL)
?
Yeah, but gcc thinks it is smarter than us...
Probably it drops the test, assuming UB cannot happen.
Hmm, sounds like a GGC bug to me then. Not sure how to fix this then.
I don't see a clear bug at this point. We are talking about the C expression
__same_type((void*)0, (void*)0)? 0 : sizeof((void*)0)/sizeof(*((void*0))
This expression is valid (assuming __same_type works, which is a GCC extension), and should return 0. As of now, I have no indication that this expression does not return 0. Also, it is true that this expression contains the suspicious pattern "sizeof(void*)/sizeof(void)", which is does not calculate the size of any array. GCC is free to emit as much warnings is it wants for any kind of expressions. From a C standard point of view, it's just a "quality of implementation" issue, and an implementation that emits useless warnings is of low quality, but not non-conforming.
In this case, we requested that gcc refuses to compile if it emits any kind of warning, which instructs gcc to reject programs that would be valid according to the C standard, but are deemed to be "likely incorrect".
I suggest to file a bug against gcc complaining about a "spurious warning", and using "-Werror -Wno-error-sizeof-pointer-div" until gcc is adapted to not emit the warning about the pointer division if the result is not used.
Regards,
Michael Karcher