How to not make a function safe

This code comes from the actual sources of the last PHP release (ext/sockets/sockets.c). It's probable that this code has been here like, forever:

First, yes, this is for real a static variable in the C module, those guys don't know about either of the const or static keyword.

   /* inet_ntop should be used instead of inet_ntoa */                                                       
   int inet_ntoa_lock = 0;

   /* ... */

Then they wrap getpeername:

   PHP_FUNCTION(socket_getpeername)
   {
       /* ... */
       if (getpeername(php_sock->bsd_socket, sa, &salen) < 0) {
           PHP_SOCKET_ERROR(php_sock, "unable to retrieve peer name", errno);
           RETURN_FALSE;
       }

so far so good. Or maybe not so good.

       switch (sa->sa_family) {
           case AF_INET:
               sin = (struct sockaddr_in *) sa;
               while (inet_ntoa_lock == 1);
               inet_ntoa_lock = 1;

Riiiiiight, locks 101, you fail.

               addr_string = inet_ntoa(sin->sin_addr);
               inet_ntoa_lock = 0;

QUICK ! let's release the lock before we actually use addr_string !

               zval_dtor(arg2);
               ZVAL_STRING(arg2, addr_string, 1);
               /*... */

And you know the best of it ? Of course that code is totally useless since^[1]:

   $ grep -wc inet_ntoa **/*.[hc]|grep -v :0
   ext/sockets/sockets.c:4
   ext/standard/basic_functions.c:1
   ext/standard/dns.c:2
   main/network.c:1
   sapi/cgi/fastcgi.c:1
   sapi/tux/php_tux.c:1

Those guys are priceless. Especially when you consider the number of 50-liners to implement inet_ntop that lie around.