[gecode-users] Using LocalHandles and LocalObjects with External Resources

[Peter Backeman]

Hello, 

I've implemented a custom propagator and brancher which are sharing a data-structure (a matrix of values), To share the structure in an efficient (and convenient) way I have looked at using LocalHandle and LocalObject. In MPG (Sec 31.4, page 391) this is described how to be implemented, however I am doing something wrong because I keep on getting some kind of memory error.

My main problem is with the notice for disposal (since external resources are used). If I do not use home.notice(*this, AP_DISPOSE) (line 17 in attached file), my program does run without errors, but I suspect it might lead to memory leaks. I've tried figuring out how this should work, but I have yet to find a full example using LocalHandle/LocalObject (i.e. together with a model) and no previous issues around this.

I'm attaching a minimum failing example (main.cpp), I'm compiling it on ubuntu using g++ version 5.4.0. and Gecode version 5.0.0 (I'm fairly sure, do not know how to exactly check this) using the following command:
	g++ -g -o main src/main.cpp -lgecodedriver -lgecodegist -lgecodesearch -lgecodeminimodel -lgecodeint -lgecodekernel -lgecodesupport
and when running it I receive the following error (gdb output):
-----------------------------------------------------------------------------
Program received signal SIGSEGV, Segmentation fault.
Gecode::VarImp<Gecode::Int::IntVarImpConf>::update (sub=<synthetic pointer>, home=...) at ./gecode/kernel/core.hpp:4438
4438	./gecode/kernel/core.hpp: No such file or directory.
(gdb) where
#0  Gecode::VarImp<Gecode::Int::IntVarImpConf>::update (sub=<synthetic pointer>, home=...) at ./gecode/kernel/core.hpp:4438
#1  Gecode::Space::update (sub=0x64e380, this=0x64e220) at ./gecode/kernel/var-imp.hpp:484
#2  Gecode::Space::_clone (this=0x63c6a0, share_data=share_data at entry=true, share_info=share_info at entry=true) at gecode/kernel/core.cpp:584
#3  0x00007ffff776b813 in Gecode::Space::clone (share_info=true, share_data=true, this=<optimized out>) at ./gecode/kernel/core.hpp:3262
#4  Gecode::Search::Sequential::BAB::next (this=0x64db38) at ./gecode/search/sequential/bab.hh:149
#5  Gecode::Search::WorkerToEngine<Gecode::Search::Sequential::BAB>::next (this=0x64db30) at ./gecode/search/support.hh:86
#6  0x0000000000411ad9 in Gecode::Search::Base<MyScript>::next (this=<optimized out>) at /usr/local/include/gecode/search/base.hpp:51
#7  Gecode::Driver::ScriptBase<Gecode::Driver::IgnoreStepOption<Gecode::IntMinimizeSpace> >::runMeta<MyScript, Gecode::BAB, Gecode::SizeOptions, Gecode::Driver::EngineToMeta> (o=..., s=0x63c6a0)
    at /usr/local/include/gecode/driver/script.hpp:360
#8  0x0000000000408e15 in Gecode::Driver::ScriptBase<Gecode::Driver::IgnoreStepOption<Gecode::IntMinimizeSpace> >::run<MyScript, Gecode::BAB, Gecode::SizeOptions> (o=..., s=0x0)
    at /usr/local/include/gecode/driver/script.hpp:274
#9  0x0000000000405536 in main (argc=1, argv=0x7fffffffe0d8) at src/main.cpp:63
-----------------------------------------------------------------------------

Any ideas on what might be the problem is greatly appreciated. My guess is that perhaps the destructor of the LocalHandle (LH) class have to make sure dispose is called on the LocalObject (LHO), however my skills in C++  and Gecode are not enough to know how I can try this. If someone just have an implementation using LocalHandles/LocalObjects which is working, just letting me have a look on that would be very helpful!

Best regards,
Peter Backeman 
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