Fix decrRefCount() prototype from void to robj pointer.

decrRefCount used to get its argument as a void* pointer in order to be
used as destructor where a 'void free_object(void*)' prototype is
expected. However this made simpler to introduce bugs by freeing the
wrong pointer. This commit fixes the argument type and introduces a new
wrapper called decrRefCountVoid() that can be used when the void*
argument is needed.

src/aof.c

@@ -456,7 +456,7 @@ struct redisClient *createFakeClient(void) {
     c->reply_bytes = 0;
     c->obuf_soft_limit_reached_time = 0;
     c->watched_keys = listCreate();
-    listSetFreeMethod(c->reply,decrRefCount);
+    listSetFreeMethod(c->reply,decrRefCountVoid);
     listSetDupMethod(c->reply,dupClientReplyValue);
     initClientMultiState(c);
     return c;

src/networking.c

@@ -89,17 +89,17 @@ redisClient *createClient(int fd) {
     c->reply = listCreate();
     c->reply_bytes = 0;
     c->obuf_soft_limit_reached_time = 0;
-    listSetFreeMethod(c->reply,decrRefCount);
+    listSetFreeMethod(c->reply,decrRefCountVoid);
     listSetDupMethod(c->reply,dupClientReplyValue);
     c->bpop.keys = dictCreate(&setDictType,NULL);
     c->bpop.timeout = 0;
     c->bpop.target = NULL;
     c->io_keys = listCreate();
     c->watched_keys = listCreate();
-    listSetFreeMethod(c->io_keys,decrRefCount);
+    listSetFreeMethod(c->io_keys,decrRefCountVoid);
     c->pubsub_channels = dictCreate(&setDictType,NULL);
     c->pubsub_patterns = listCreate();
-    listSetFreeMethod(c->pubsub_patterns,decrRefCount);
+    listSetFreeMethod(c->pubsub_patterns,decrRefCountVoid);
     listSetMatchMethod(c->pubsub_patterns,listMatchObjects);
     if (fd != -1) listAddNodeTail(server.clients,c);
     initClientMultiState(c);

src/object.c

@@ -215,9 +215,7 @@ void incrRefCount(robj *o) {
     o->refcount++;
 }
 
-void decrRefCount(void *obj) {
-    robj *o = obj;
-
+void decrRefCount(robj *o) {
     if (o->refcount <= 0) redisPanic("decrRefCount against refcount <= 0");
     if (o->refcount == 1) {
         switch(o->type) {
@@ -234,6 +232,13 @@ void decrRefCount(void *obj) {
     }
 }
 
+/* This variant of decrRefCount() gets its argument as void, and is useful
+ * as free method in data structures that expect a 'void free_object(void*)'
+ * prototype for the free method. */
+void decrRefCountVoid(void *o) {
+    decrRefCount(o);
+}
+
 /* This function set the ref count to zero without freeing the object.
  * It is useful in order to pass a new object to functions incrementing
  * the ref count of the received object. Example:

src/redis.h

@@ -989,7 +989,8 @@ void discardTransaction(redisClient *c);
 void flagTransaction(redisClient *c);
 
 /* Redis object implementation */
-void decrRefCount(void *o);
+void decrRefCount(robj *o);
+void decrRefCountVoid(void *o);
 void incrRefCount(robj *o);
 robj *resetRefCount(robj *obj);
 void freeStringObject(robj *o);

src/t_list.c

@@ -275,7 +275,7 @@ void listTypeConvert(robj *subject, int enc) {
 
     if (enc == REDIS_ENCODING_LINKEDLIST) {
         list *l = listCreate();
-        listSetFreeMethod(l,decrRefCount);
+        listSetFreeMethod(l,decrRefCountVoid);
 
         /* listTypeGet returns a robj with incremented refcount */
         li = listTypeInitIterator(subject,0,REDIS_TAIL);