On Wed, Jun 18, 2014 at 09:18:10AM +0200, Florian Weimer wrote:
> On 06/17/2014 05:00 PM, Jakub Jelinek wrote:
>
> >>>GCC will likely not optimize it away at this point, but having code with
> >>>undefined behavior is just asking for future trouble. Just use "" instead?
> >>
> >>It's always const and may lack sufficient alignment. The former isn't a
> >>problem in C++ (I think), but the alignment is an issue.
> >
> >Alignment for what? You don't specify any alignment to the C qsort,
>
> You're returning a T *, not a void *, and C++ requires that pointers are
> properly aligned even if they aren't dereferenced.
C qsort doesn't return anything and the comparison function returns int.
extern void qsort (void *__base, size_t __nmemb, size_t __size,
__compar_fn_t __compar) __nonnull ((1, 4));
It is the C qsort that has undefined behavior if the 1st or 4th argument is
NULL. So I don't see what is wrong on:
qsort (ptr ? (void *) ptr : "", nmemb, sizeof (*ptr), compar);
Jakub
