On 12/20/16 02:00, Markus Trippelsdorf wrote:
> On 2016.12.20 at 01:30 -0800, H. Peter Anvin wrote:
>> I'd strongly prefer a non-data-dependent solution, specifically adding
>> at the top of sort_relocs():
>>
>> if (!r->count)
>> return;
>>
>> However, by my reading of the C and POSIX standards, this is a gcc
>> error: qsort() should do nothing if the count is zero.
>
> No, it is invoking undefined behavior.
H
> Notice the nonnull attribute in /usr/include/stdlib.h:
>
> 739 /* Sort NMEMB elements of BASE, of SIZE bytes each,
> 740 using COMPAR to perform the comparisons. */
> 741 extern void qsort (void *__base, size_t __nmemb, size_t __size,
> 742 __compar_fn_t __compar) __nonnull ((1, 4));
>
> But feel free to revert my patch and add your solution.
Well, s/gcc/glibc/ then.
> The qsort() function shall sort an array of nel objects, the
> initial element of which is pointed to by base. The size of
> each object, in bytes, is specified by the width argument. If
> the nel argument has the value zero, the comparison function
> pointed to by compar shall not be called and no rearrangement
> shall take place.
-hpa
