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Re: [xml] [PATCH] less-than character and HTML parser module

On Tue, Apr 14, 2015 at 05:43:42PM +0200, Christian Schoenebeck wrote:

On Tuesday 14 April 2015 17:50:51 you wrote:

If anything like this does get put in, it should only be if it is a
configurable option that is disabled by default - an xml parser should
only accept a strictly-conforming document by default. Adding support for
‘broken’ html because other (weak) parsers allow it is not a good plan as
it causes divergence from the standard.


There you go; you find the updated patch attached. It now requires 
HTML_PARSE_RECOVER option to be set for recovering from stand-alone less-than 
characters.


That sounds fine *except* it doesn't raise an error.
The parser knows it's a broken construct that must be pointed out.

thinkpad2:~/XML -> ./xmllint --html tst.html
tst.html:3: HTML parser error : htmlParseStartTag: invalid element name
<p> blah < booh </p>
          ^
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd";>
<html>
<body>
<p> blah 
</p>
</body>
</html>
thinkpad2:~/XML -> ./xmllint --html --recover tst.html
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd";>
<html>
<body>
<p> blah &lt; booh </p>
</body>
</html>
thinkpad2:~/XML -> 

 the fact that we worked around a broken start tag construct must be reported.
Whether we do that with the recovery option or not is less important IMHO.

 It sounds a bit weird to handle that error case as one of the main content
cases, I would still be tempted to go into htmlParseStartTag, get the
error reported, but push corrective data instead in recover mode.

 Can we get a v3 ? :-)

  thanks

Daniel



Best regards,
Christian Schoenebeck



diff -u libxml2-2.9.1+dfsg1.orig/HTMLparser.c libxml2-2.9.1+dfsg1/HTMLparser.c
--- libxml2-2.9.1+dfsg1.orig/HTMLparser.c     2015-04-14 13:05:01.000000000 +0200
+++ libxml2-2.9.1+dfsg1/HTMLparser.c  2015-04-14 18:22:41.143973776 +0200
@@ -2948,8 +2948,10 @@
 
 
 /**
- * htmlParseCharData:
+ * htmlParseCharDataInternal:
  * @ctxt:  an HTML parser context
+ * @prep:  optional character to be prepended to text, 0 if no character
+ *         shall be prepended
  *
  * parse a CharData section.
  * if we are within a CDATA section ']]>' marks an end of section.
@@ -2958,12 +2960,15 @@
  */
 
 static void
-htmlParseCharData(htmlParserCtxtPtr ctxt) {
-    xmlChar buf[HTML_PARSER_BIG_BUFFER_SIZE + 5];
+htmlParseCharDataInternal(htmlParserCtxtPtr ctxt, char prep) {
+    xmlChar buf[HTML_PARSER_BIG_BUFFER_SIZE + 6];
     int nbchar = 0;
     int cur, l;
     int chunk = 0;
 
+    if (prep)
+     buf[nbchar++] = prep;
+
     SHRINK;
     cur = CUR_CHAR(l);
     while (((cur != '<') || (ctxt->token == '<')) &&
@@ -3043,6 +3048,21 @@
 }
 
 /**
+ * htmlParseCharData:
+ * @ctxt:  an HTML parser context
+ *
+ * parse a CharData section.
+ * if we are within a CDATA section ']]>' marks an end of section.
+ *
+ * [14] CharData ::= [^<&]* - ([^<&]* ']]>' [^<&]*)
+ */
+
+static void
+htmlParseCharData(htmlParserCtxtPtr ctxt) {
+    htmlParseCharDataInternal(ctxt, 0);
+}
+
+/**
  * htmlParseExternalID:
  * @ctxt:  an HTML parser context
  * @publicID:  a xmlChar** receiving PubidLiteral
@@ -4157,14 +4177,24 @@
          }
 
          /*
-          * Third case :  a sub-element.
+          * Third case : (unescaped) stand-alone less-than character.
+          *              Only if HTML_PARSE_RECOVER option is set.
+          */
+         else if (ctxt->recovery && (CUR == '<') &&
+                  (IS_BLANK_CH(NXT(1)) || (NXT(1) == '='))) {
+             NEXT;
+             htmlParseCharDataInternal(ctxt, '<');
+         }
+
+         /*
+          * Fourth case :  a sub-element.
           */
          else if (CUR == '<') {
              htmlParseElement(ctxt);
          }
 
          /*
-          * Fourth case : a reference. If if has not been resolved,
+          * Fifth case : a reference. If if has not been resolved,
           *    parsing returns it's Name, create the node
           */
          else if (CUR == '&') {
@@ -4172,7 +4202,7 @@
          }
 
          /*
-          * Fifth case : end of the resource
+          * Sixth case : end of the resource
           */
          else if (CUR == 0) {
              htmlAutoCloseOnEnd(ctxt);
@@ -4567,7 +4597,17 @@
          }
 
          /*
-          * Third case :  a sub-element.
+          * Third case : (unescaped) stand-alone less-than character.
+          *              Only if HTML_PARSE_RECOVER option is set.
+          */
+         else if (ctxt->recovery && (CUR == '<') &&
+                  (IS_BLANK_CH(NXT(1)) || (NXT(1) == '='))) {
+             NEXT;
+             htmlParseCharDataInternal(ctxt, '<');
+         }
+
+         /*
+          * Fourth case :  a sub-element.
           */
          else if (CUR == '<') {
              htmlParseElementInternal(ctxt);
@@ -4578,7 +4618,7 @@
          }
 
          /*
-          * Fourth case : a reference. If if has not been resolved,
+          * Fifth case : a reference. If if has not been resolved,
           *    parsing returns it's Name, create the node
           */
          else if (CUR == '&') {
@@ -4586,7 +4626,7 @@
          }
 
          /*
-          * Fifth case : end of the resource
+          * Sixth case : end of the resource
           */
          else if (CUR == 0) {
              htmlAutoCloseOnEnd(ctxt);



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-- 
Daniel Veillard      | Open Source and Standards, Red Hat
veillard redhat com  | libxml Gnome XML XSLT toolkit  http://xmlsoft.org/
http://veillard.com/ | virtualization library  http://libvirt.org/
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