Comments

Author: nielsdos

ext/dom/nodelist.c

@@ -34,6 +34,7 @@
 static zend_always_inline void objmap_cache_release_cached_obj(dom_nnodemap_object *objmap)
 {
 	if (objmap->cached_obj) {
+		/* Since the DOM is a tree there can be no cycles. */
 		if (GC_DELREF(&objmap->cached_obj->std) == 0) {
 			zend_objects_store_del(&objmap->cached_obj->std);
 		}
@@ -227,7 +228,11 @@ PHP_METHOD(DOMNodeList, item)
 			DOM_RET_OBJ(itemnode, &ret, objmap->baseobj);
 			if (cache_itemnode) {
 				/* Hold additional reference for the cache, must happen before releasing the cache
-				 * because we might be the last reference holder. */
+				 * because we might be the last reference holder.
+				 * Instead of storing and copying zvals, we store the object pointer directly.
+				 * This saves us some bytes because a pointer is smaller than a zval.
+				 * This also means we have to manually refcount the objects here, and remove the reference count
+				 * in reset_objmap_cache() and the destructor. */
 				dom_object *cached_obj = Z_DOMOBJ_P(return_value);
 				GC_ADDREF(&cached_obj->std);
 				/* If the tag is stale, all cached data is useless. Otherwise only the cached object is useless. */

ext/dom/tests/DOMDocument_getElementsByTagName_liveness.phpt

@@ -10,6 +10,32 @@ $root = $doc->documentElement;
 
 $i = 0;
 
+/* Note that the list is live. The explanation for the output is as follows:
+   Before the loop we have the following (writing only the attributes):
+   1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
+
+   Now the loop starts, the current element is marked with a V. $i == 0:
+   V
+   1  2  3  4  5  6  7  8  9  10  11  12  13  14  15
+   1 gets printed. $i == 0, which is even, so 1 gets removed, which results in:
+   V
+   2  3  4  5  6  7  8  9  10  11  12  13  14  15
+   Note that everything shifted to the left.
+   Because the list is live, the current element pointer still refers to the first index, which now corresponds to element with attribute 2.
+   Now the foreach body ends, which means we go to the next element, which is now 3 instead of 2.
+      V
+   2  3  4  5  6  7  8  9  10  11  12  13  14  15
+   3 gets printed. $i == 1, which is odd, so nothing happens and we move on to the next element:
+         V
+   2  3  4  5  6  7  8  9  10  11  12  13  14  15
+   4 gets printed. $i == 2, which is even, so 4 gets removed, which results in:
+         V
+   2  3  5  6  7  8  9  10  11  12  13  14  15
+   Note again everything shifted to the left.
+   Now the foreach body ends, which means we go to the next element, which is now 6 instead of 5.
+            V
+   2  3  5  6  7  8  9  10  11  12  13  14  15
+   6 gets printed, etc... */
 foreach ($doc->getElementsByTagName('e') as $node) {
 	print $node->getAttribute('i') . ' ';
 	if ($i++ % 2 == 0)