NamedNodeMapAttributeList assertion bug

[Hemligt Namn]

Dear Xalan developers,

I believe there is a bug in the NamedNodeMapAttributeList constructor: an assertion fails if the attribute map is empty.

The assertion prevents me from serializing this to XML:
<page>
  <paragraph>
  </paragraph>
</page>

Please find below excerpts from the relevant source code, a stack trace, a patch, example code that triggers the assertion.

(Studying Xalan's SVN history, it seems the bug was introduced in late June, 2008. Also, as far as I've seen, there must be two nested tags with no attributes for the bug to appear. --- Perhaps that's why this has not been fixed before.)

Regards,
Magnus


--------------------------------------------
Excerpt from relevant source code
--------------------------------------------

http://svn.apache.org/repos/asf/xalan/c/trunk/src/xalanc/PlatformSupport/NamedNodeMapAttributeList.cpp

NamedNodeMapAttributeList::NamedNodeMapAttributeList(
            const XalanNamedNodeMap&    theMap,
            MemoryManagerType&          theManager) :
    ParentType(),
    m_nodeMap(theMap),
    m_lastIndex(theMap.getLength() - 1),
    m_memoryManager(theManager)
{
    assert(theMap.getLength() != 0);  <-- fails
}


trunk\xml-xalan\c\src\xalanc\xmlsupport\formattertreewalker.cpp:

FormatterTreeWalker::startNode(const XalanNode*        node)
    :
    :
    case XalanNode::ELEMENT_NODE:
        {
            const XalanElement*    theElementNode =
#if defined(XALAN_OLD_STYLE_CASTS)
                (const XalanElement*)node;
#else
                static_cast<const XalanElement*>(node);
#endif

            const XalanNamedNodeMap*    atts = theElementNode->getAttributes();
            assert(atts != 0);

            NamedNodeMapAttributeList    theAttributeList(*atts, m_memoryManager);  <--- above assertion means that there *must* be an attribute?

            m_formatterListener.startElement(c_wstr(theElementNode->getNodeName()),
                                             theAttributeList);
        }
        break;
    :
    :

--------------------------------------------
Stack trace
--------------------------------------------

msvcr80d.dll!_wassert(const wchar_t * expr=0x095aa254, const wchar_t * filename=0x095aa290, unsigned int lineno=56)  Line 384    C
Xalan-C_1_10D.dll!xalanc_1_10::NamedNodeMapAttributeList::NamedNodeMapAttributeList(const xalanc_1_10::XalanNamedNodeMap & theMap={...}, xercesc_3_0::MemoryManager & theManager={...})  Line 56 + 0x2e bytes    C++
Xalan-C_1_10D.dll!xalanc_1_10::FormatterTreeWalker::startNode(const xalanc_1_10::XalanNode * node=0x09ff07e8)  Line 89 + 0x13 bytes    C++
Xalan-C_1_10D.dll!xalanc_1_10::TreeWalker::traverse(const xalanc_1_10::XalanNode * pos=0x09ff07e8, const xalanc_1_10::XalanNode * parent=0x09fee6c0)  Line 159 + 0x13 bytes    C++
Xalan-C_1_10D.dll!xalanc_1_10::TreeWalker::traverseSubtree(const xalanc_1_10::XalanNode * pos=0x09fee6c0)  Line 265    C++
my-test-program.exe!XmlPageBuilder_tests::Xalan_assertion::test_method()  Line 39 + 0x15 bytes    C++

--------------------------------------------
Patch? (Removing assertion, setting index to 0)
--------------------------------------------
Index: NamedNodeMapAttributeList.cpp
===================================================================
--- NamedNodeMapAttributeList.cpp    (revision 679080)
+++ NamedNodeMapAttributeList.cpp    (working copy)
@@ -50,10 +50,10 @@
             MemoryManagerType&          theManager) :
     ParentType(),
     m_nodeMap(theMap),
-    m_lastIndex(theMap.getLength() - 1),
+    m_lastIndex(theMap.getLength() > 0 ? theMap.getLength() - 1 : 0),
     m_memoryManager(theManager)
 {
-    assert(theMap.getLength() != 0);
+    //assert(theMap.getLength() != 0); -- no, allow 0
 }


--------------------------------------------
Example code that reproduces the crash
--------------------------------------------

XalanTransformer oXalanTransformer;
XalanDocumentBuilder* pBuilder = oXalanTransformer.createDocumentBuilder();
ContentHandler* pContentHandler = pBuilder->getContentHandler();

AttributesImpl xAttributes;
const XalanDOMChar xNullChar = 0;

pContentHandler->startDocument();
pContentHandler->startElement( & xNullChar, & xNullChar, L"page", xAttributes );
pContentHandler->startElement( & xNullChar, & xNullChar, L"paragraph", xAttributes ); // nested tag required for assertion to fail
pContentHandler->endElement( & xNullChar, & xNullChar, L"paragraph" );
pContentHandler->endElement( & xNullChar, & xNullChar, L"page" );
pContentHandler->endDocument();

_STL::stringstream sstream;
XalanStdOutputStream xStream( sstream );
XalanOutputStreamPrintWriter xPrintWriter( xStream );
FormatterToXML xFormatter( xPrintWriter );
FormatterTreeWalker oTreeWalker( xFormatter );

const XalanNode* const    pFunctionNode = pBuilder->getDocument()->getFirstChild();

xFormatter.setShouldWriteXMLHeader(false);
xFormatter.startDocument(); // (required)
oTreeWalker.traverseSubtree( pFunctionNode );
xFormatter.endDocument();

[David Bertoni]

Hemligt Namn wrote:

> Dear Xalan developers,
>
> I believe there is a bug in the NamedNodeMapAttributeList constructor:
> an assertion fails if the attribute map is empty.
>
> The assertion prevents me from serializing this to XML:
> <page>
>   <paragraph>
>   </paragraph>
> </page>
>
> Please find below excerpts from the relevant source code, a stack trace,
> a patch, example code that triggers the assertion.

I put the assertion in because the rest of the logic will fail if the
attribute list is empty.  I think I need to just fix the other logic.

Can you open a Jira issue a attach an archive with the necessary inputs
to reproduce the problem?

Dave

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[Hemligt Namn]

Hi Dave,

Thanks for opening a Jira issue and providing a patch that quickly.

(I otherwise intended to open an issue today.)
(In case I should upload some of the original information (steps to reproduce?), just let me know.)

Regards,
Magnus

On Mon, Sep 8, 2008 at 10:45 PM, David Bertoni <dbertoni@...> wrote:

Hemligt Namn wrote:

Dear Xalan developers,

I believe there is a bug in the NamedNodeMapAttributeList constructor: an assertion fails if the attribute map is empty.

The assertion prevents me from serializing this to XML:
<page>
 <paragraph>
 </paragraph>
</page>

Please find below excerpts from the relevant source code, a stack trace, a patch, example code that triggers the assertion.

I put the assertion in because the rest of the logic will fail if the attribute list is empty.  I think I need to just fix the other logic.

Can you open a Jira issue a attach an archive with the necessary inputs to reproduce the problem?

Dave

[David Bertoni]

Hemligt Namn wrote:
> Hi Dave,
>
> Thanks for opening a Jira issue and providing a patch that quickly.
>
> (I otherwise intended to open an issue today.)
> (In case I should upload some of the original information (steps to
> reproduce?), just let me know.)
If you could attach your code snippet as a file and grant a license to
the ASF, that would be great.  I'm starting a regression test suite for
Xalan-C, and I'd like to include your snippet.

Also, if you can test the patch, I will commit it once I know it works
for you, then we can close the issue.

Thanks!

Dave

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