If a Result is freed after it's Client, allow it to free the Client's

underlying MYSQL* structure to prevent leaks. This will be pretty
rare but needs to be accounted for.

Author: brianmario

ext/mysql2/client.c

@@ -185,9 +185,10 @@ static VALUE nogvl_close(void *ptr) {
 static void rb_mysql_client_free(void * ptr) {
   mysql_client_wrapper *wrapper = (mysql_client_wrapper *)ptr;
 
-  if (wrapper->refcount == 0) {
-    nogvl_close(wrapper);
+  wrapper->freed = 1;
+  nogvl_close(wrapper);
 
+  if (wrapper->refcount == 0) {
     xfree(wrapper->client);
     xfree(ptr);
   }
@@ -203,6 +204,7 @@ static VALUE allocate(VALUE klass) {
   wrapper->connected = 0; /* means that a database connection is open */
   wrapper->initialized = 0; /* means that that the wrapper is initialized */
   wrapper->refcount = 0;
+  wrapper->freed = 0;
   wrapper->client = (MYSQL*)xmalloc(sizeof(MYSQL));
   return obj;
 }

ext/mysql2/client.h

@@ -39,6 +39,7 @@ typedef struct {
   int connected;
   int initialized;
   int refcount;
+  int freed;
   MYSQL *client;
 } mysql_client_wrapper;
 

ext/mysql2/result.c

@@ -73,6 +73,10 @@ static void rb_mysql_result_free_result(mysql2_result_wrapper * wrapper) {
     mysql_free_result(wrapper->result);
     wrapper->resultFreed = 1;
     wrapper->client_wrapper->refcount--;
+    if (wrapper->client_wrapper->refcount == 0 && wrapper->client_wrapper->freed) {
+      xfree(wrapper->client_wrapper->client);
+      xfree(wrapper->client_wrapper);
+    }
   }
 }