I guess, you're right - for naive implementation it should fall with error, not a segfault. Maybe I just add a check for realloc result. As for qsort implement

I guess, you're right - for naive implementation it should fall with error, not a segfault. Maybe I just add a check for realloc result. As for qsort implementation - I was confused by glibc sources ;-) What I've found was a slow but in-place implementation, and what you've shown me is an actual implementation that invokes an in-place variant when allocation was failed: tmp = malloc (size); __set_errno (save); if (tmp == NULL) { /* Couldn't get space, so use the slower algorithm that doesn't need a temporary array. */ _quicksort (b, n, s, cmp, arg); return; } Thanks for feedback!