Warning when using qsort in C

Question

I wrote my comparison function

int cmp(const int * a,const int * b)
 {
   if (*a==*b)
   return 0;
else
  if (*a < *b)
    return -1;
else
    return 1;
}         


        

Answer 1

According to the man page, a __compar_fn_t is defined as: typedef int(*) __compar_fn_t (const void *, const void *)

Your cmp specifies int* parameters. It doesn't like that, but is only listed as a warning.

Answer 2

The cmp function's prototype must be

int cmp(const void* a, const void* b);

You can either cast it in the invocation of qsort (not recommended):

qsort(currentCases, round, sizeof(int), (int(*)(const void*,const void*))cmp);

or casts the void-pointers to int-pointers in cmp (the standard approach):

int cmp(const void* pa, const void* pb) {
   int a = *(const int*)pa;
   int b = *(const int*)pb;
   ...