[cfe-commits] [PATCH] Expressions have lvalues and rvalues

[Ted Kremenek]

On Oct 12, 2008, at 4:26 AM, Zhongxing Xu wrote:

> This is consistent with C. But what we should care about is that we  
> have two kinds of evaluations of expressions: lvalue evaluation and  
> rvalue evaluation. lvalue evaluation returns the address of the  
> object that the lvalue refers to. rvalue evaluation returns the  
> value previously assigned to the object. This indicates we should  
> have:
>
> AbstractVal GRExprEngine::VisitRValue(Expr* E)  (corresponds to the  
> current GRExprEngine::Visit())
> and
> LocVal GRExprEngine::VisitLValue(Expr*)      (corresponds to the  
> GRExprEngine::VisitLValue() in my patch)
>
> VisitRValue returns an AbstractValue because an expression's rvalue  
> can either be location value or non-location value. And  
> VisitLValue() always returns location value (in practice it might  
> also return UnknownVal or UndefinedVal).

Yep, this is exactly what we do now.  I don't know if renaming Visit  
to VisitRValue is worth it.  Probably would make the code far more  
self-documenting.

> lvalue-to-rvalue conversion
> I think this should not bother us too much. It only indicates that  
> we should do a rvalue-evaluation of the expression.

Agreed.