Issue 146 in soar: Null Pointer Crash on Invalid Soar Code

[so...@googlecode.com]

Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 146 by alex.tur...@soartech.com: Null Pointer Crash on Invalid
Soar Code
http://code.google.com/p/soar/issues/detail?id=146

The following brief Soar code will crash Soar with a Null Pointer Exception.

...
(<s> ^smem.command.store <store>)
-->
(<s> ^smem.command.store <store> -)
...

This is invalid soar code in that it won't do what you might think it
should, remove the store WM on the smem.command link. Instead since this
is on the RHS and is dot notation, it will expand <s> ^smem.command.store
to:

sp {apply*successful-store
(state <s> ^storage <storage> ^smem <s*1>)
(<s*1> ^command <c*1>)
(<c*1> ^store <store>)
-->
(<s> ^smem <s*2> +)
(<s*2> ^command <c*2> +)
(<c*2> ^store <store> -)
}

And so it will fail in prefmem.cpp:remove_preference_from_tm:373 because
slot* s is NULL and it tries to access the element all_preferences on the
slot pointer. Ideally this should fail more gracefully than crashing Soar
but unfortunately it does.

Attached is Soar code which consistently exposes this issue. Just launch
the Soar Java Debugger and source the file and try to run for an infinite
number of decisions. It will crash on the third decision cycle because of
this issue.

Attachments:
SMemClearResult_SimpleFloat-Bug.soar 884 bytes

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