[PATCH] Division by zero

[Jordan Rose]

On Jul 4, 2014, at 1:15 , Anders Rönnholm <Anders.Ronnholm at evidente.se> wrote:

>> Huh. So, I changed it back to the way it was:
>> 
>> SVal Val = State->getRawSVal(*L);
>> if (Val == S) {
>> Optional<DefinedSVal> DSV = Val.getAs<DefinedSVal>();
>>   ConstraintManager &CM = C.getConstraintManager();
>>   if (!CM.assume(State, *DSV, false))
>>     return true;
>> }
>> 
>> and tried running the tests. No failures. Then I flipped the "false" to "true" in the assume...and still no failures. So we must never be getting into that if-case!
>> 
>> What would that affect?
>> 
>> Jordan
> 
> 
> We don't get into the if-case because we never get a Loc from Sval therefore it always returns false and our tests are passed.
> 
> Optional<Loc> L = S.getAs<Loc>();
>  if (!L)
>    return false;

Um. Right, we shouldn't get a Loc at that point. But we don't need a Loc. We just need whatever NonLoc symbol is there, and we can check to see if that is 0. Why did we need a Loc again?

Anyway, we shouldn't have features that don't show up in the tests. I think this code was either trying to avoid emitting duplicate messages if the denominator is known to be 0 already (which won't happen because that's a fatal error), or trying to avoid adding the symbol to the map if it's known not to be 0 (which is not what it's doing now, or at least not what it says it's doing). The latter is kind of useful but it's just optimization.

Jordan

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