sort a 2d array using qsort - seg fault

Question

I'm trying to sort a 2d array of strings a simplified version looks like, ( I dont want to change the datatype of "nameArray" to "char *nameArray[4]" )

#include <sys/types.h>
#include <stdio.h>

int cstring_cmp(const void *a, const void *b)
{
    const char **ia = (const char **)a;
    const char **ib = (const char **)b;
    return strcasecmp(*ia, *ib);
}

int Test()
{
   char nameArray[4][10]={"test","alpha","Hyper","city"};
 //  int nElem = sizeof(nameArray)/sizeof(char *);
   int index = 0;

   //printf("nElem =%d\n", nElem);

   for(index=0; index < 4; index++)
   {
      printf("-> %s\n", nameArray[index]);
   }

   qsort( &nameArray[0], 4, sizeof(nameArray[0]), cstring_cmp);

   printf("After sort\n");

   for(index=0; index < 4; index++)
   {
      printf("-> %s\n", nameArray[index]);
   }
   return 0 ;
}

( UPDATE: changed so that I'm directly using the value(4) instead of calculating nElem. My problem is getting the qsort to working. )

Answer 1

The arguments to the comparison function are just pointers, rather than pointers to pointers.

You also don't need to cast I believe, since the parameters are void *, you can just assign them to the local variables and the compiler takes care of them.

Try this:

int cstring_cmp(const void *a, const void *b)
{
   const char *ia = a;
   const char *ib = b;
   return strcasecmp(ia, ib);
}

Or even get rid of the local variables if you don't need them (only need them if you're planning on adding more code to the comparison function):

int cstring_cmp(const void *a, const void *b)
{
  return strcasecmp(a, b);
}

Answer 2

int cstring_cmp(const void *a, const void *b)
{
  return strcmp(a, b);
}