multi: reuse WinSock events variable in Curl_multi_wait

Since the struct is quite large (1 long and 10 ints) we
declare it once at the beginning of the function instead
of multiple times inside loops to avoid stack movements.

Reviewed-by: Viktor Szakats
Reviewed-by: Daniel Stenberg

Closes #5886

lib/multi.c

@@ -1095,6 +1095,7 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
   bool ufds_malloc = FALSE;
 #else
   struct pollfd pre_poll;
+  WSANETWORKEVENTS wsa_events;
   DEBUGASSERT(multi->wsa_event != WSA_INVALID_EVENT);
 #endif
 
@@ -1295,18 +1296,17 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
       for(i = 0; i < extra_nfds; i++) {
         unsigned short mask = 0;
 #ifdef USE_WINSOCK
-        WSANETWORKEVENTS events = {0};
+        wsa_events.lNetworkEvents = 0;
         mask = extra_fds[i].revents;
         if(WSAEnumNetworkEvents(extra_fds[i].fd, multi->wsa_event,
-                                &events) == 0) {
-          if(events.lNetworkEvents & (FD_READ|FD_ACCEPT|FD_CLOSE))
+                                &wsa_events) == 0) {
+          if(wsa_events.lNetworkEvents & (FD_READ|FD_ACCEPT|FD_CLOSE))
             mask |= CURL_WAIT_POLLIN;
-          if(events.lNetworkEvents & (FD_WRITE|FD_CONNECT|FD_CLOSE))
+          if(wsa_events.lNetworkEvents & (FD_WRITE|FD_CONNECT|FD_CLOSE))
             mask |= CURL_WAIT_POLLOUT;
-          if(events.lNetworkEvents & FD_OOB)
+          if(wsa_events.lNetworkEvents & FD_OOB)
             mask |= CURL_WAIT_POLLPRI;
-
-          if(ret && events.lNetworkEvents != 0)
+          if(ret && wsa_events.lNetworkEvents != 0)
             retcode++;
         }
         WSAEventSelect(extra_fds[i].fd, multi->wsa_event, 0);
@@ -1320,7 +1320,6 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
         if(r & POLLPRI)
           mask |= CURL_WAIT_POLLPRI;
 #endif
-
         extra_fds[i].revents = mask;
       }
 
@@ -1334,13 +1333,13 @@ static CURLMcode Curl_multi_wait(struct Curl_multi *multi,
 
           for(i = 0; i < MAX_SOCKSPEREASYHANDLE; i++) {
             if(bitmap & (GETSOCK_READSOCK(i) | GETSOCK_WRITESOCK(i))) {
-              WSANETWORKEVENTS events = {0};
+              wsa_events.lNetworkEvents = 0;
               if(WSAEnumNetworkEvents(sockbunch[i], multi->wsa_event,
-                                      &events) == 0) {
-                if(ret && events.lNetworkEvents != 0)
+                                      &wsa_events) == 0) {
+                if(ret && wsa_events.lNetworkEvents != 0)
                   retcode++;
               }
-              if(ret && !timeout_ms && !events.lNetworkEvents) {
+              if(ret && !timeout_ms && wsa_events.lNetworkEvents == 0) {
                 if((bitmap & GETSOCK_READSOCK(i)) &&
                    SOCKET_READABLE(sockbunch[i], 0) > 0)
                   retcode++;