[geos-devel] Memory Leak In GEOSIntersection_r

Mick Orridge m.orridge at gismosoftware.co.uk
Fri Jan 23 16:41:28 PST 2015

This is my first post here, so feel free to let me know if I should be 
doing things differently.

I've been using the nightly snapshot from 4/1/2015 to generate Voronoi 
polygons and then clip them to the UK coastline on Windows 8.1 with 
VS2013. After processing several 100,000 polygons with 
GEOSIntersection_r my laptop was running out of memory.

I've investigated further and it looks like the Edges rejected by 
OverlayOp::insertUniqueEdges in OverlayOp.cpp are not being deleted.

My, not very elegant, solution to fix this is to add a new method to 
OverlayOp as follows:-

OverlayOp::deleteOrphanedEdges(vector<Edge*> *edges, const Envelope *env)
     for (size_t i = 0, n = edges->size(); i < n; ++i)
         Edge *e = (*edges)[i];
         if (env && !env->intersects(e->getEnvelope())) delete e;

and then call this just before exiting the method 
OverlayOp::computeOverlay(OverlayOp::OpCode opCode)

I don't really understand enough about the data structures to know if 
this is a valid fix or not. If somebody who does understand how this 
works could have a look at things I'd appreciate it.

There is also a small memory leak of a geomFactory in init/finishGEOS(). 
The only way I can see to fix this is to introduce a reference count and 
then null the static pointer when it reaches 0. Happy to have a look at 
fixing this if this seems a reasonable approach.


Mick Orridge

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