Introduce Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE.

Proposed by Tim Peters.

Modules/_ssl.c

@@ -377,8 +377,10 @@ check_socket_and_wait_for_timeout(PySocketSockObject *s, int writing)
 		return SOCKET_HAS_BEEN_CLOSED;
 
 	/* Guard against socket too large for select*/
+#ifndef Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE
 	if (s->sock_fd >= FD_SETSIZE)
 		return SOCKET_INVALID;
+#endif
 
 	/* Construct the arguments to select */
 	tv.tv_sec = (int)s->sock_timeout;

Modules/socketmodule.c

@@ -396,7 +396,14 @@ static int taskwindow;
 static PyTypeObject sock_type;
 
 /* Can we call select() with this socket without a buffer overrun? */
+#ifdef Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE
+/* Platform can select file descriptors beyond FD_SETSIZE */
+#define IS_SELECTABLE(s) 1
+#else
+/* POSIX says selecting file descriptors beyond FD_SETSIZE
+   has undefined behaviour. */
 #define IS_SELECTABLE(s) ((s)->sock_fd < FD_SETSIZE)
+#endif
 
 static PyObject*
 select_error(void)

PC/pyconfig.h

@@ -572,4 +572,9 @@ Py_NO_ENABLE_SHARED to find out.  Also support MS_NO_COREDLL for b/w compat */
 
 /* Define if you have the thread library (-lthread).  */
 /* #undef HAVE_LIBTHREAD */
+
+/* WinSock does not use a bitmask in select, and uses
+   socket handles greater than FD_SETSIZE */
+#define Py_SOCKET_FD_CAN_BE_GE_FD_SETSIZE
+
 #endif /* !Py_CONFIG_H */