[libxml2] Make xmlNewSAXParserCtx take a const sax handler

[Nick Wellnhofer <nwellnhof src gnome org>]

commit 65dc8a63aca578945e6121b4e5b93621d1733d9e
Author: Nick Wellnhofer <wellnhofer aevum de>
Date:   Thu Sep 1 00:13:19 2022 +0200

    Make xmlNewSAXParserCtx take a const sax handler
    
    Also improve documentation.

 HTMLparser.c                | 8 +++++---
 include/libxml/HTMLparser.h | 4 ++--
 include/libxml/parser.h     | 3 ++-
 parserInternals.c           | 9 +++++----
 4 files changed, 14 insertions(+), 10 deletions(-)
---
diff --git a/HTMLparser.c b/HTMLparser.c
index d5fb6ae3..f29138ac 100644
--- a/HTMLparser.c
+++ b/HTMLparser.c
@@ -5047,7 +5047,8 @@ htmlParseDocument(htmlParserCtxtPtr ctxt) {
  */
 
 static int
-htmlInitParserCtxt(htmlParserCtxtPtr ctxt, htmlSAXHandler *sax, void *userData)
+htmlInitParserCtxt(htmlParserCtxtPtr ctxt, const htmlSAXHandler *sax,
+                   void *userData)
 {
     if (ctxt == NULL) return(-1);
     memset(ctxt, 0, sizeof(htmlParserCtxt));
@@ -5181,13 +5182,14 @@ htmlNewParserCtxt(void)
  * @sax:  SAX handler
  * @userData:  user data
  *
- * Allocate and initialize a new parser context.
+ * Allocate and initialize a new SAX parser context. If userData is NULL,
+ * the parser context will be passed as user data.
  *
  * Returns the htmlParserCtxtPtr or NULL in case of allocation error
  */
 
 htmlParserCtxtPtr
-htmlNewSAXParserCtxt(htmlSAXHandlerPtr sax, void *userData)
+htmlNewSAXParserCtxt(const htmlSAXHandler *sax, void *userData)
 {
     xmlParserCtxtPtr ctxt;
 
diff --git a/include/libxml/HTMLparser.h b/include/libxml/HTMLparser.h
index 9fa01be1..e0e96833 100644
--- a/include/libxml/HTMLparser.h
+++ b/include/libxml/HTMLparser.h
@@ -114,8 +114,8 @@ XMLPUBFUN void XMLCALL
 XMLPUBFUN htmlParserCtxtPtr XMLCALL
                        htmlNewParserCtxt(void);
 XMLPUBFUN htmlParserCtxtPtr XMLCALL
-                       htmlNewSAXParserCtxt(htmlSAXHandlerPtr sax,
-                                        void *userData);
+                       htmlNewSAXParserCtxt(const htmlSAXHandler *sax,
+                                            void *userData);
 
 XMLPUBFUN htmlParserCtxtPtr XMLCALL
                        htmlCreateMemoryParserCtxt(const char *buffer,
diff --git a/include/libxml/parser.h b/include/libxml/parser.h
index f96148b5..ca5c93c9 100644
--- a/include/libxml/parser.h
+++ b/include/libxml/parser.h
@@ -990,7 +990,8 @@ XMLPUBFUN int XMLCALL
 XMLPUBFUN xmlParserCtxtPtr XMLCALL
                xmlNewParserCtxt        (void);
 XMLPUBFUN xmlParserCtxtPtr XMLCALL
-               xmlNewSAXParserCtxt     (xmlSAXHandlerPtr sax, void *userData);
+               xmlNewSAXParserCtxt     (const xmlSAXHandler *sax,
+                                        void *userData);
 XMLPUBFUN int XMLCALL
                xmlInitParserCtxt       (xmlParserCtxtPtr ctxt);
 XMLPUBFUN void XMLCALL
diff --git a/parserInternals.c b/parserInternals.c
index eb12e629..4e119535 100644
--- a/parserInternals.c
+++ b/parserInternals.c
@@ -1455,7 +1455,7 @@ xmlNewInputFromFile(xmlParserCtxtPtr ctxt, const char *filename) {
  */
 
 static int
-xmlInitSAXParserCtxt(xmlParserCtxtPtr ctxt, xmlSAXHandlerPtr sax,
+xmlInitSAXParserCtxt(xmlParserCtxtPtr ctxt, const xmlSAXHandler *sax,
                      void *userData)
 {
     xmlParserInputPtr input;
@@ -1765,13 +1765,14 @@ xmlNewParserCtxt(void)
  * @sax:  SAX handler
  * @userData:  user data
  *
- * Allocate and initialize a new SAX parser context.
+ * Allocate and initialize a new SAX parser context. If userData is NULL,
+ * the parser context will be passed as user data.
  *
- * Returns the xmlParserCtxtPtr or NULL
+ * Returns the xmlParserCtxtPtr or NULL if memory allocation failed.
  */
 
 xmlParserCtxtPtr
-xmlNewSAXParserCtxt(xmlSAXHandlerPtr sax, void *userData)
+xmlNewSAXParserCtxt(const xmlSAXHandler *sax, void *userData)
 {
     xmlParserCtxtPtr ctxt;