static void php_wddx_pop_element(void *user_data, const XML_Char *name)
{
	st_entry 			*ent1, *ent2;
	wddx_stack 			*stack = (wddx_stack *)user_data;
	HashTable 			*target_hash;
	zend_class_entry 	**pce;
	zval				*obj;
	zval				*tmp;
	TSRMLS_FETCH();

/* OBJECTS_FIXME */
	if (stack->top == 0) {
		return;
	}

	if (!strcmp(name, EL_STRING) || !strcmp(name, EL_NUMBER) ||
		!strcmp(name, EL_BOOLEAN) || !strcmp(name, EL_NULL) ||
	  	!strcmp(name, EL_ARRAY) || !strcmp(name, EL_STRUCT) ||
		!strcmp(name, EL_RECORDSET) || !strcmp(name, EL_BINARY) ||
		!strcmp(name, EL_DATETIME)) {
		wddx_stack_top(stack, (void**)&ent1);

		if (!ent1->data) {
			if (stack->top > 1) {
				stack->top--;
			} else {
				stack->done = 1;
			}
			efree(ent1);
			return;
		}

		if (!strcmp(name, EL_BINARY)) {
			int new_len=0;
			unsigned char *new_str;
 
 			new_str = php_base64_decode(Z_STRVAL_P(ent1->data), Z_STRLEN_P(ent1->data), &new_len);
 			STR_FREE(Z_STRVAL_P(ent1->data));
			Z_STRVAL_P(ent1->data) = new_str;
			Z_STRLEN_P(ent1->data) = new_len;
 		}
 
 		/* Call __wakeup() method on the object. */
		if (Z_TYPE_P(ent1->data) == IS_OBJECT) {
			zval *fname, *retval = NULL;

			MAKE_STD_ZVAL(fname);
			ZVAL_STRING(fname, "__wakeup", 1);

			call_user_function_ex(NULL, &ent1->data, fname, &retval, 0, 0, 0, NULL TSRMLS_CC);

			zval_dtor(fname);
			FREE_ZVAL(fname);
			if (retval) {
				zval_ptr_dtor(&retval);
			}
		}

		if (stack->top > 1) {
			stack->top--;
			wddx_stack_top(stack, (void**)&ent2);

			/* if non-existent field */
			if (ent2->type == ST_FIELD && ent2->data == NULL) {
				zval_ptr_dtor(&ent1->data);
				efree(ent1);
				return;
			}

			if (Z_TYPE_P(ent2->data) == IS_ARRAY || Z_TYPE_P(ent2->data) == IS_OBJECT) {
				target_hash = HASH_OF(ent2->data);

				if (ent1->varname) {
					if (!strcmp(ent1->varname, PHP_CLASS_NAME_VAR) &&
						Z_TYPE_P(ent1->data) == IS_STRING && Z_STRLEN_P(ent1->data) &&
						ent2->type == ST_STRUCT && Z_TYPE_P(ent2->data) == IS_ARRAY) {
						zend_bool incomplete_class = 0;

						zend_str_tolower(Z_STRVAL_P(ent1->data), Z_STRLEN_P(ent1->data));
						if (zend_hash_find(EG(class_table), Z_STRVAL_P(ent1->data),
										   Z_STRLEN_P(ent1->data)+1, (void **) &pce)==FAILURE) {
							incomplete_class = 1;
							pce = &PHP_IC_ENTRY;
						}

						/* Initialize target object */
						MAKE_STD_ZVAL(obj);
						object_init_ex(obj, *pce);

						/* Merge current hashtable with object's default properties */
						zend_hash_merge(Z_OBJPROP_P(obj),
										Z_ARRVAL_P(ent2->data),
										(void (*)(void *)) zval_add_ref,
										(void *) &tmp, sizeof(zval *), 0);

						if (incomplete_class) {
							php_store_class_name(obj, Z_STRVAL_P(ent1->data), Z_STRLEN_P(ent1->data));
						}

						/* Clean up old array entry */
						zval_ptr_dtor(&ent2->data);

						/* Set stack entry to point to the newly created object */
						ent2->data = obj;

						/* Clean up class name var entry */
						zval_ptr_dtor(&ent1->data);
					} else if (Z_TYPE_P(ent2->data) == IS_OBJECT) {
						zend_class_entry *old_scope = EG(scope);

						EG(scope) = Z_OBJCE_P(ent2->data);
						Z_DELREF_P(ent1->data);
						add_property_zval(ent2->data, ent1->varname, ent1->data);
						EG(scope) = old_scope;
					} else {
						zend_symtable_update(target_hash, ent1->varname, strlen(ent1->varname)+1, &ent1->data, sizeof(zval *), NULL);
					}
					efree(ent1->varname);
				} else	{
					zend_hash_next_index_insert(target_hash, &ent1->data, sizeof(zval *), NULL);
				}
			}
			efree(ent1);
		} else {
			stack->done = 1;
		}
	} else if (!strcmp(name, EL_VAR) && stack->varname) {
		efree(stack->varname);
		stack->varname = NULL;
	} else if (!strcmp(name, EL_FIELD)) {
		st_entry *ent;
		wddx_stack_top(stack, (void **)&ent);
		efree(ent);
		stack->top--;
	}
}

The product dereferences a pointer that it expects to be valid but is NULL.