Curl_memchr: zero length input can't match

 *                            | (__| |_| |  _ <| |___

 *                             \___|\___/|_| \_\_____|

 *

 * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.

 * Copyright (C) 1998 - 2018, Daniel Stenberg, <daniel@haxx.se>, et al.

 *

 * This software is licensed as described in the file COPYING, which

 * you should have received as part of this distribution. The terms

void *

Curl_memrchr(const void *s, int c, size_t n)

{

  if(n > 0) {

    const unsigned char *p = s;

    const unsigned char *q = s;

        return (void *)p;

      p--;

    }

  }

  return NULL;

}