Opened 19 years ago

Last modified 17 years ago

#738 closed defect

It seems OGR uses reference counting inconsistently, what result in memory leak. — at Version 2

Reported by: mbrudka@… Owned by: Mateusz Łoskot
Priority: normal Milestone: 1.4.2
Component: OGR_SRS Version: unspecified
Severity: normal Keywords:
Cc: warmerdam

Description (last modified by warmerdam)

OGR uses reference counting for some object to manage the life cycle of objects as well as to decrease OGR memory requirements. In particular SpatialReferenceSystems are reference counted. While reference counting is consistent in OGRProj4CT, namely OGRSpatialReference are deleted when counter falls below 1, in OGRGeometry eg. OGRGeometry::~OGRGeometry and OGRGeometry::assignSpatialReference a counter is released without checking if OGRSpatialReference should be deleted. This may result in memory leak.

SAMPLE FIX/WORKAROUND:

The quick fix is to check if reference counter falls below 1 and eventually delete the object eg.

OGRGeometry::~OGRGeometry()
{
   if( poSRS != NULL )
   {
       if ( poSRS->Dereference() <= 0 )
         delete poSRS;
   }
}

However, a better way to manage reference counted objects is to use consistently in GDAL intrusive smart pointers. If the dependency on boost libraries is accepted, then I propose to use boost::instrusive_ptr (http://www.boost.org/libs/smart_ptr/intrusive_ptr.html). If this dependency is for some reason undesirable, then a simple template (boost::instrusive_ptr is 273 lines long) for such pointers can be written. I strongly recommend such technique, as this is simple way to avoid related with reference counted memory management.

Change History (1)

comment:2 by warmerdam, 17 years ago

Cc: warmerdam added
Description: modified (diff)
Milestone: 1.4.2
Owner: changed from warmerdam to Mateusz Łoskot
Priority: highnormal
Severity: criticalnormal

Matuesz,

Could you review this, and see if you can reproduce a reference counting bug? As you can imagine, I'm still not keen on the boost auto_ptr solution. :-)

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