c - Sorting an array of pointers -

am right in thinking fine treat pointer int purposes of sorting array of pointers, e.g.

qsort(ptrs, n, sizeof(void*), int_cmp); 

i want sort ptrs ascertain whether there duplicates, irrespective of type of thing pointer pointing to, qsort precursor doing that.

my int_cmp() pretty standard, e.g.

int int_cmp(const void *a, const void *b) {     const int *ia = (const int *)a; // casting pointer types     const int *ib = (const int *)b;      /* integer comparison: returns negative if b >     , positive if > b */     return *ia  - *ib; } 

it seems work in unit-tests there reason why considering ptr int may cause problems such scenario may have overlooked?

no, you're not right @ all, unless want sort pointers address. actual address has meaning though, that's unlikely.

for detecting duplicate pointers, should compare pointers such, that's well-defined.

i go solution using uintptr_t:

static int order_pointers(const void *pa, const void *pb) {   const uintptr_t = *(void **) pa, b = *(void **) pb;    return < b ? -1 : > b; } 

haven't tested this, should work.

the conversion uintptr_t necessary since cannot validly compare random pointers. quoth c99 draft standard, §6.5.8.5:

when 2 pointers compared, result depends on relative locations in address space of objects pointed to. if 2 pointers object or incomplete types both point same object, or both point 1 past last element of same array object, compare equal. if objects pointed members of same aggregate object, pointers structure members declared later compare greater pointers members declared earlier in structure, , pointers array elements larger subscript values compare greater pointers elements of same array lower subscript values. pointers members of same union object compare equal. if expression p points element of array object , expression q points last element of same array object, pointer expression q+1 compares greater p. in other cases, behavior undefined.

i bolded final sentence since that's applies here.