You don't actually need a cast to write a qsort comparison function, because void * is implicitly converted to and from other pointer types in C. Eg:

  int compare_xyzzy(const void *a, const void *b)
  {
      const struct xyzzy *sa = a;
      const struct xyzzy *sb = b;

      return (sa->i > sb->i) - (sa->i < sb->i);
  }

On the other hand, pointer casts are needed if you want to write a function like strchr() (where you can pass a const-qualified pointer, but want to return an unqualified pointer for the case where an unqualified pointer was passed).

D'oh! You're right, of course.

If you want to write "generic" function in C, use #define to generate static function for your specific type. But it much much better to use C++ or Rust instead.

Example: https://svnweb.freebsd.org/base/head/sys/sys/tree.h?revision...