ws2_32: Null select() should fail with WSAEINVAL.

dlls/ws2_32/socket.c

@@ -3496,7 +3496,11 @@ static struct pollfd *fd_sets_to_poll( const WS_fd_set *readfds, const WS_fd_set
     if (writefds) count += writefds->fd_count;
     if (exceptfds) count += exceptfds->fd_count;
     *count_ptr = count;
-    if (!count) return NULL;
+    if (!count)
+    {
+        SetLastError(WSAEINVAL);
+        return NULL;
+    }
     if (!(fds = HeapAlloc( GetProcessHeap(), 0, count * sizeof(fds[0]))))
     {
         SetLastError( ERROR_NOT_ENOUGH_MEMORY );
@@ -3619,7 +3623,7 @@ int WINAPI WS_select(int nfds, WS_fd_set *ws_readfds,
     TRACE("read %p, write %p, excp %p timeout %p\n",
           ws_readfds, ws_writefds, ws_exceptfds, ws_timeout);
 
-    if (!(pollfds = fd_sets_to_poll( ws_readfds, ws_writefds, ws_exceptfds, &count )) && count)
+    if (!(pollfds = fd_sets_to_poll( ws_readfds, ws_writefds, ws_exceptfds, &count )))
         return SOCKET_ERROR;
 
     if (ws_timeout)

dlls/ws2_32/tests/sock.c

@@ -1943,6 +1943,17 @@ static void test_select(void)
     FD_ZERO(&readfds);
     FD_ZERO(&writefds);
     FD_ZERO(&exceptfds);
+
+    SetLastError(0);
+    ret = select(maxfd+1, 0, 0, 0, &select_timeout);
+    ok ( (ret == SOCKET_ERROR), "expected SOCKET_ERROR, got %i\n", ret);
+    ok ( GetLastError() == WSAEINVAL, "expected WSAEINVAL, got %i\n", ret);
+
+    SetLastError(0);
+    ret = select(maxfd+1, &readfds, &writefds, &exceptfds, &select_timeout);
+    ok ( (ret == SOCKET_ERROR), "expected SOCKET_ERROR, got %i\n", ret);
+    ok ( GetLastError() == WSAEINVAL, "expected WSAEINVAL, got %i\n", ret);
+
     FD_SET(INVALID_SOCKET, &readfds);
     SetLastError(0);
     ret = select(maxfd+1, &readfds, &writefds, &exceptfds, &select_timeout);