dns: fix cares memory leak

PR-URL: nodejs#43912
Refs: nodejs#39735
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Matteo Collina <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>
Reviewed-By: Darshan Sen <[email protected]>

Author: theanarkh

src/cares_wrap.cc

@@ -1428,6 +1428,7 @@ static void Query(const FunctionCallbackInfo<Value>& args) {
 
 
 void AfterGetAddrInfo(uv_getaddrinfo_t* req, int status, struct addrinfo* res) {
+  auto cleanup = OnScopeLeave([&]() { uv_freeaddrinfo(res); });
   std::unique_ptr<GetAddrInfoReqWrap> req_wrap {
       static_cast<GetAddrInfoReqWrap*>(req->data)};
   Environment* env = req_wrap->env();
@@ -1488,8 +1489,6 @@ void AfterGetAddrInfo(uv_getaddrinfo_t* req, int status, struct addrinfo* res) {
     argv[1] = results;
   }
 
-  uv_freeaddrinfo(res);
-
   TRACE_EVENT_NESTABLE_ASYNC_END2(
       TRACING_CATEGORY_NODE2(dns, native), "lookup", req_wrap.get(),
       "count", n, "verbatim", verbatim);