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From "Michael Chisholm (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (XALANC-742) XalanVector assignment operator crash bug
Date Wed, 10 Apr 2013 19:15:16 GMT

    [ https://issues.apache.org/jira/browse/XALANC-742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13628136#comment-13628136
] 

Michael Chisholm commented on XALANC-742:
-----------------------------------------

Well I figured out the hard way that Xerces' memory manager still has to be set up when a
XalanVector goes out of scope, because XalanVector's dtor needs it to release memory.  So
here's a more correct version of the demo app:

#include <xercesc/util/PlatformUtils.hpp>
#include <xalanc/Include/XalanVector.hpp>

using namespace xercesc;
using namespace xalanc;

int main(int argc, char* argv[])
{
	XMLPlatformUtils::Initialize();

	{
		XalanVector<int> vec1;
		XalanVector<int> vec2(XalanMemMgrs::getDefaultXercesMemMgr(), 5);

		vec1 = vec2;
	}
	
	XMLPlatformUtils::Terminate();
	
	return 0;
}

I have also fixed it in my own way, basically by making the assignment a no-op if both vectors
are empty:

Index: XalanVector.hpp
===================================================================
--- XalanVector.hpp     (revision 1466627)
+++ XalanVector.hpp     (working copy)
@@ -809,6 +809,9 @@

         if (&theRHS != this)
         {
+            if (empty() && theRHS.empty())
+                return *this;
+
             if (m_allocation < theRHS.m_size)
             {
                 ThisType    theTemp(theRHS,*m_memoryManager);

This patch seems to have resolved the problem for me.

                
> XalanVector assignment operator crash bug
> -----------------------------------------
>
>                 Key: XALANC-742
>                 URL: https://issues.apache.org/jira/browse/XALANC-742
>             Project: XalanC
>          Issue Type: Bug
>          Components: XalanC
>    Affects Versions: CurrentCVS, 1.11
>         Environment: Tested on Windows 7 and RHEL5
>            Reporter: Michael Chisholm
>            Assignee: Steven J. Hathaway
>            Priority: Critical
>
> When assigning an empty XalanVector to another, a NULL dereference and crash results.
 Specifically, the std::copy() statement copies to this->begin(), which returns NULL when
the vector is empty.
> Here is simple demo code:
> #include <xercesc/util/PlatformUtils.hpp>
> #include <xalanc/Include/XalanVector.hpp>
> using namespace xercesc;
> using namespace xalanc;
> int main(int argc, char* argv[])
> {
> 	XMLPlatformUtils::Initialize();
> 	XalanVector<int> vec1;
> 	XalanVector<int> vec2(XalanMemMgrs::getDefaultXercesMemMgr(), 5);
> 	vec1 = vec2;
> 	XMLPlatformUtils::Terminate();
> 	
> 	return 0;
> }

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