[ expat-Bugs-596931 ] XML_ParseReset and memory leaks

noreply@sourceforge.net noreply@sourceforge.net
Sun Aug 18 18:54:02 2002

Bugs item #596931, was opened at 2002-08-18 20:25
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Nobody/Anonymous (nobody)
>Assigned to: Karl Waclawek (kwaclaw)
Summary: XML_ParseReset and memory leaks

Initial Comment:
The problem:
XML_ParseReset function does not reset the parser 
correctly, resulting in memory leaks. These leaks can 
be observed using the windows task manager while 
running the sample code below.  

Expat version: 1.95.4
Platform: win200

Sample Application:

include <string.h>
#include "expat.h"

char buffer[] = "<?xml version=\1.0\?><request 

void main()
   XML_Parser parser = XML_ParserCreate(NULL);

   while ( true )
      int ret = XML_Parse( parser, buffer, strlen(buffer ), 1);
      if( ret == 0 )

      ret = XML_ParserReset( parser, NULL );
      if( ret == 0 )


>Comment By: Karl Waclawek (kwaclaw)
Date: 2002-08-18 21:53

Logged In: YES 

Yes, this is a bug, as discussed on expat-discuss.
I have attached a first patch - still to be tested.

The problem was that dtdDestroy was not called in 
XML_ParserReset, since dtd.scaffold was NULL.
Then, when dtdInit() was later called in parserInit,
the pointers were overwritten - leading to memory leaks.

This was a logic problem - the original reason for checking 
dtd.scaffold was to prevent double-destroying the dtd 
structure, but dtd.scaffold was only set when there was a
content model.

I changed this by introducing the new functions dtdReset() 
and hashTableClear(). There were other logic errors too, that
would not show up in the test case given, but would have
led to memory leaks in other situations:
- freeBindingList and inheritedBindings were overwritten
- tagStack and freeTagList were overwritten
- groupSize and  groupConnector were overwritten

Other changes:
- There is no reason to have dtdDestroy/dtdReset conditional 
  on XML_DTD.
- The unknownEncodingHandler(Data) is not reset anymore,
  since this is not really a dynamic handler anyway.
- I also removed dtdInit() from parserInit() and it is now called 
- The return type of XML_ParserReset was changed from int
  to XML_Bool. This should not be much of a problem, since
  it is binary compatible, and XML_ParserReset is new
  and not even documented yet.
- A couple of minor code cleanups were performed too,
  not to confuse the reader.


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