cmp_t
static inline char *med3(char *, char *, char *, cmp_t *);
void qsort(void *a, size_t n, size_t es, cmp_t *cmp);
med3(char *a, char *b, char *c, cmp_t *cmp)
qsort(void *a, size_t n, size_t es, cmp_t *cmp)
typedef int cmp_t(const void *, const void *);
void qsort(void *, size_t, size_t, cmp_t *);