Clear pointers after free as a precaution.

src/common/prng.c

@@ -40,6 +40,7 @@ static void tls_prng_deinit(void *ptr)
 static void tls_prng_deinit_main()
 {
 	tls_prng_deinit(pthread_getspecific(tls_prng_key));
+	(void)pthread_setspecific(tls_prng_key, NULL);
 }
 
 static void tls_prng_init()

src/common/slab/slab.c

@@ -463,14 +463,8 @@ int slab_cache_init(slab_cache_t* cache, size_t bufsize)
 		return -1;
 	}
 
-	cache->empty = 0;
+	memset(cache, 0, sizeof(slab_cache_t));
 	cache->bufsize = bufsize;
-	cache->slabs_free = cache->slabs_full = 0;
-	cache->color = 0;
-
-	/* Initialize stats */
-	cache->stat_allocs = cache->stat_frees = 0;
-
 	dbg_mem("%s: created cache of size %zu\n",
 	          __func__, bufsize);
 

src/libknot/zone/zone-tree.c

@@ -336,7 +336,8 @@ void knot_zone_tree_free(knot_zone_tree_t **tree)
 	if (tree == NULL || *tree == NULL) {
 		return;
 	}
-	hattrie_free((*tree));
+	hattrie_free(*tree);
+	*tree = NULL;
 }
 
 /*----------------------------------------------------------------------------*/