generic swapping function in C

gswap.c

void gswap(void *v1, void *v2, size_t sz) {
  char *c1 = v1;
  char *c2 = v2;
  char  tmp;
  
  while(sz--) {
    tmp   = *c1;
    *c1++ = *c2;
    *c2++ = tmp;
  }
}