[cfe-dev] Weak function pointers (was "SymbolRef and SVal confusion")

[Richard]

So you mean something like the attached diff? I am not so sure, it makes some things simpler, but I don't like the duplicated messy checks for weak function regions in SimpleSValBuilder and SimpleConstraintManager. What do you reckon? I actually remembered to include a working test this time too.


On 21 Jan 2013, at 18:48, Jordan Rose <jordan_rose at apple.com> wrote:

> 
> On Jan 20, 2013, at 9:00 , Richard <tarka.t.otter at googlemail.com> wrote:
> 
>>>> +
>>>> +  void setWeakSymbol(const SymbolExtent *S) {
>>>> +    // Only weak functions can have symbols.
>>>> +    assert(cast<ValueDecl>(FD)->isWeak());
>>>> +    WeakSym = S;
>>>> +  }
>>> 
>>> MemRegions need to be immutable, so the setWeakSymbol() is not going to work.  Can we just have the symbol associated with the FunctionTextRegion when it gets created?
>> 
>> I would like to do this, but I don't see how it is possible easily. The SymbolExtent requires the FunctionTextRegion in its constructor, and I don't see a nice way to get hold of the SymbolManager in the FunctionTextRegions constructor to create it. Any suggestions here?
> 
> My new thought on this is that this should just be created lazily by SValBuilder and that it doesn't even need to live on the region. SValBuilder::getWeakSymbolForRegion, or something like that. 
> 
> I'll talk to Anna and Ted about what to rename SymbolExtent and SymbolMetadata to properly include this new usage; if you have any opinions, I'd love to hear them!
> 
> SymbolExtent:
> - based on the region itself
> - does not get invalidated
> - live as long as the region is live (in theory)
> 
> SymbolMetadata:
> - based on the region contents
> - is invalidated along with region contents
> - live as long as the region is live and some checker is interested
> 
> Jordan

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