Fix GH-17500: Segfault with requesting nodeName on nameless doctype

Author: nielsdos

ext/dom/node.c

@@ -98,11 +98,17 @@ int dom_node_node_name_read(dom_object *obj, zval *retval)
 		}
 		case XML_DOCUMENT_TYPE_NODE:
 		case XML_DTD_NODE:
+			if (nodep->name) {
+				ZVAL_STRING(retval, (const char *) nodep->name);
+			} else {
+				ZVAL_EMPTY_STRING(retval);
+			}
+			break;
 		case XML_PI_NODE:
 		case XML_ENTITY_DECL:
 		case XML_ENTITY_REF_NODE:
 		case XML_NOTATION_NODE:
-			ZVAL_STRING(retval, (char *) nodep->name);
+			ZVAL_STRING(retval, (const char *) nodep->name);
 			break;
 		case XML_CDATA_SECTION_NODE:
 			ZVAL_STRING(retval, "#cdata-section");

ext/dom/tests/gh17500.phpt

@@ -0,0 +1,14 @@
+--TEST--
+GH-17500 (Segfault with requesting nodeName on nameless doctype)
+--EXTENSIONS--
+dom
+--FILE--
+<?php
+
+$doc = new DOMDocument();
+$doc->loadHTML("<!DOCTYPE>", LIBXML_NOERROR);
+var_dump($doc->doctype->nodeName);
+
+?>
+--EXPECT--
+string(0) ""