Bruno Haible <[EMAIL PROTECTED]> writes: > you are now assuming an in-place sorting algorithm. If a libc were > to implement qsort by use of mergesort (and temporary storage), such > a sorting algorithm would pass you two pointers to hol_entrys in > different array.
A minor quibble: the C standard (both C89 and C99) does not allow such an implementation for qsort; it requires that the arguments to the comparison function be bona fide pointers into the originally-specified array. > To make this portable, I see two options: > - Sort an array of 'hol_entry*' instead of an array of 'hol_entry'; > then you can be sure the hol_entrys stay in place. Or > - Add a field 'array_index' to the hol_entry struct. Fill these fields > right before calling qsort. I agree with this suggestion. Even though the standard requires that qsort be in-place, it does not require that qsort must behave by swapping elements in the naive way. Also, it's possible that the C library is buggy in this area (glibc used to have such a bug), as the point is fairly obscure. So a fix is necessary, and the two options you mention both should work.
