[libxml2] xmlParseBalancedChunkMemory must not be called with NULL doc

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 2e8cc66d8fbf573e48a37382bf354dfdbc20ef08
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Sat May 30 15:40:08 2020 +0200

    xmlParseBalancedChunkMemory must not be called with NULL doc
    
    There is no way to avoid memory leaks without a document to hold the
    namespace list.

 parser.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/parser.c b/parser.c
index 4cc58b11..046f1cec 100644
--- a/parser.c
+++ b/parser.c
@@ -13176,7 +13176,7 @@ xmlParseExternalEntity(xmlDocPtr doc, xmlSAXHandlerPtr sax, void *user_data,
 
 /**
  * xmlParseBalancedChunkMemory:
- * @doc:  the document the chunk pertains to
+ * @doc:  the document the chunk pertains to (must not be NULL)
  * @sax:  the SAX handler block (possibly NULL)
  * @user_data:  The user data returned on SAX callbacks (possibly NULL)
  * @depth:  Used for loop detection, use 0
@@ -13628,7 +13628,7 @@ xmlParseInNodeContext(xmlNodePtr node, const char *data, int datalen,
 #ifdef LIBXML_SAX1_ENABLED
 /**
  * xmlParseBalancedChunkMemoryRecover:
- * @doc:  the document the chunk pertains to
+ * @doc:  the document the chunk pertains to (must not be NULL)
  * @sax:  the SAX handler block (possibly NULL)
  * @user_data:  The user data returned on SAX callbacks (possibly NULL)
  * @depth:  Used for loop detection, use 0
@@ -13700,6 +13700,7 @@ xmlParseBalancedChunkMemoryRecover(xmlDocPtr doc, xmlSAXHandlerPtr sax,
     } else {
        xmlCtxtUseOptionsInternal(ctxt, XML_PARSE_NODICT, NULL);
     }
+    /* doc == NULL is only supported for historic reasons */
     if (doc != NULL) {
        newDoc->intSubset = doc->intSubset;
        newDoc->extSubset = doc->extSubset;
@@ -13716,6 +13717,7 @@ xmlParseBalancedChunkMemoryRecover(xmlDocPtr doc, xmlSAXHandlerPtr sax,
     }
     xmlAddChild((xmlNodePtr) newDoc, newRoot);
     nodePush(ctxt, newRoot);
+    /* doc == NULL is only supported for historic reasons */
     if (doc == NULL) {
        ctxt->myDoc = newDoc;
     } else {
@@ -13785,6 +13787,7 @@ xmlParseBalancedChunkMemoryRecover(xmlDocPtr doc, xmlSAXHandlerPtr sax,
     xmlFreeParserCtxt(ctxt);
     newDoc->intSubset = NULL;
     newDoc->extSubset = NULL;
+    /* This leaks the namespace list if doc == NULL */
     newDoc->oldNs = NULL;
     xmlFreeDoc(newDoc);