I am trying to use qsort to a dynamically allocated array of strings.
It has two problems:

1) it doesn't sort
2) it gives garbage when using long data
if I use ./prog1 red blue green
warray = red
warray = blue
warray = green

./prog1 red blue green ddddddddddddddddddddddddddddddd
warray = (null)
warray = (null)
warray = (null)
warray = (null)

What did I do wrong?

Thanks,

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

int main (int argc, char *argv[])
{
char **warray;
size_t numleft;
size_t temp;
size_t lhold;
size_t lstr=0;

  numleft=(size_t)(argc-1); /* number of words to put in array */
  warray=malloc(numleft * sizeof(*warray));

  if (warray == NULL) {
    printf("can't allocate memory for warray\n");
    exit(EXIT_FAILURE);
  }
  for (temp=0; temp < numleft; temp++) { /* get length of longest word
*/
    lhold = strlen (argv[temp+1]);
    if (lhold > lstr)
      lstr = lhold;
    warray[temp] = argv[temp+1]; /* put argument into array */
  }
  qsort(warray, lstr, numleft, strcmp);

  for (lstr=0;lstr<numleft;lstr++) {
    printf("warray = %s\n",warray[lstr]);
  }
return 0;

qsort() calls its comparison function with the ADDRESSES of two objects
in the array.  The array you have is an array of character pointers,
so you're actually getting the addresses of those pointers passed to
strcmp, which ought to be pretty much pure garbage.

Suggestion:
        int ptr_to_strcmp(void *v1, void *v2) {
                const char **s1 = v1;
                const char **s2 = v2;
                return strcmp(*s1, *s2);
        }

Your second argument is supposed to be the size of each element of
warray.  It isn't.  It is the size of the longest string any element
of warray points to and is completely unrelated to the size of the
element itself.

        qsort(warray, numleft, sizeof *warray, mycomp);
--
Larry Jones