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https://issues.apache.org/jira/browse/XERCESC-2126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17005471#comment-17005471
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Scott Cantor commented on XERCESC-2126:
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I missed this when the other DOM casting was fixed, but I concur with the
proposed fix, just need to reorder the code.
Fixed in r1872122
> Type Confusion from DTDGrammar to SchemaGrammar
> -----------------------------------------------
>
> Key: XERCESC-2126
> URL: https://issues.apache.org/jira/browse/XERCESC-2126
> Project: Xerces-C++
> Issue Type: Bug
> Components: DOM
> Affects Versions: 3.0.0, 3.0.1, 3.0.2, 3.1.0, 3.1.1, 3.1.2, 3.2.0, 3.1.3,
> 3.1.4, 3.2.1, 3.2.2
> Environment: Ubuntu 16.04 LTS, Intel(R) Core(TM) i7-6700 CPU @
> 3.40GHz, 16GB
> Reporter: Yuseok Jeon
> Assignee: Scott Cantor
> Priority: Major
> Fix For: 3.2.3
>
> Attachments: Xerces-C++ Type confusion Report.pdf
>
>
> Hi all,
> Our type confusion detection tool reports a type_confusion error in the
> "xercesc/validators/schema/SchemaValidator.cpp"
> xercesc/validators/schema/SchemaValidator.cpp line 772
> 756 void SchemaValidator::preContentValidation(bool, bool validateDefAttr)
> 758 {
> 769 RefHashTableOfEnumerator<Grammar> grammarEnum =
> fGrammarResolver->getGrammarEnumerator();
> 770 while (grammarEnum.hasMoreElements())
> 771 {
> {color:red}772 SchemaGrammar& sGrammar = (SchemaGrammar&)
> grammarEnum.nextElement();{color}
> 773 if (sGrammar.getGrammarType() != Grammar::SchemaGrammarType ||
> sGrammar.getValidated())
> 774 continue;
> ……………
> }
> In the line 772, grammarEnum.nextElement() indicates object allocated as
> DTDGrammar, and it is casted into SchemaGrammar. However, since SchemaGrammar
> is not a subobject of DTDGrammar, it is violating C++ standard rules 5.2.9/11
> (down casting is undefined if the object that the pointer to be casted points
> to is not a suboject of down casting type) and causes undefined behaviors.
> There are similar type-confusion cases as below links.
> - (Xerces-c++) https://issues.apache.org/jira/browse/XERCESC-2088
> - (libstdc++) https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60734
> - (Firefox) https://bugzilla.mozilla.org/show_bug.cgi?id=1074280
> I attached detail type confusion information.
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