gai_strerror() is not thread-safe on Windows (GH-15568)

First we refactor to have only a single usage of `PHP_GAI_STRERROR()`
left; then we drop the macro in favor of calling the different
functions conditionally in an ad-hoc style.

This is necessary because the return value of `php_win32_error_to_msg`
needs to be freed by the caller.

The error messages are no more inline with other error messages, since
`gai_strerror()` apparently always appends a period and a space.

We also properly configure IPv4/v6 on Windows.  Since WSPiApi.h has been
created in 2000, so we can safely assume that it is available everywhere
nowadays.  Furthermore, `gai_strerror()` is available regardless of
whether there is IPv6 support.

Author: cmb69

main/network.c

@@ -88,10 +88,7 @@ const struct in6_addr in6addr_any = {0}; /* IN6ADDR_ANY_INIT; */
 #endif
 
 #ifdef HAVE_GETADDRINFO
-#ifdef HAVE_GAI_STRERROR
-#  define PHP_GAI_STRERROR(x) (gai_strerror(x))
-#else
-#  define PHP_GAI_STRERROR(x) (php_gai_strerror(x))
+# if !defined(PHP_WIN32) && !defined(HAVE_GAI_STRERROR)
 /* {{{ php_gai_strerror */
 static const char *php_gai_strerror(int code)
 {
@@ -129,7 +126,7 @@ static const char *php_gai_strerror(int code)
 	return "Unknown error";
 }
 /* }}} */
-#endif
+# endif
 #endif
 
 /* {{{ php_network_freeaddresses */
@@ -193,16 +190,26 @@ PHPAPI int php_network_getaddresses(const char *host, int socktype, struct socka
 # endif
 
 	if ((n = getaddrinfo(host, NULL, &hints, &res))) {
+# if defined(PHP_WIN32)
+		char *gai_error = php_win32_error_to_msg(n);
+# elif defined(HAVE_GAI_STRERROR)
+		const char *gai_error = gai_strerror(n);
+# else
+		const char *gai_error = php_gai_strerror(n)
+# endif
 		if (error_string) {
 			/* free error string received during previous iteration (if any) */
 			if (*error_string) {
 				zend_string_release_ex(*error_string, 0);
 			}
-			*error_string = strpprintf(0, "php_network_getaddresses: getaddrinfo for %s failed: %s", host, PHP_GAI_STRERROR(n));
+			*error_string = strpprintf(0, "php_network_getaddresses: getaddrinfo for %s failed: %s", host, gai_error);
 			php_error_docref(NULL, E_WARNING, "%s", ZSTR_VAL(*error_string));
 		} else {
-			php_error_docref(NULL, E_WARNING, "php_network_getaddresses: getaddrinfo for %s failed: %s", host, PHP_GAI_STRERROR(n));
+			php_error_docref(NULL, E_WARNING, "php_network_getaddresses: getaddrinfo for %s failed: %s", host, gai_error);
 		}
+# if PHP_WIN32
+		php_win32_error_msg_free(gai_error);
+# endif
 		return 0;
 	} else if (res == NULL) {
 		if (error_string) {

win32/build/config.w32

@@ -324,13 +324,9 @@ STDOUT.WriteBlankLines(1);
 /* Can we build with IPv6 support? */
 ARG_ENABLE("ipv6", "Disable IPv6 support (default is turn it on if available)", "yes");
 
-var main_network_has_ipv6 = 0;
+AC_DEFINE('HAVE_GAI_STRERROR', 1);
 if (PHP_IPV6 == "yes") {
-	main_network_has_ipv6 = CHECK_HEADER_ADD_INCLUDE("wspiapi.h", "CFLAGS") ? 1 : 0;
-}
-if (main_network_has_ipv6) {
 	STDOUT.WriteLine("Enabling IPv6 support");
-	AC_DEFINE('HAVE_GAI_STRERROR', 1);
 	AC_DEFINE('HAVE_IPV6', 1);
 }