On Dec 15, 2008, at 5:39 PM, Zhongxing Xu wrote:
> I agree in your example we should not convert p to point to the zero-
> index element. But in my example:
>
> char * p = alloca(10);
> p[1] = 3;
>
> p *is* a pointer to 'char' when we do CastRegion.
Yes, but a "char*" can be either a pointer to an array or a single
character. In this case (with alloca) we know p is a pointer to an
array of bytes, so it simplifies things, but if (for example) the
region is symbolic we don't know if the void* is a pointer to a single
character or to an array of bytes.
> And later in ArraySubscriptExpr we don't have a chance to do the
> conversion.
Not true. Just because there isn't a pointer-to-array cast in the AST
doesn't mean we can't do the conversion. We can do it when handling
the ArraySubscriptExpr:
/// VisitArraySubscriptExpr - Transfer function for array accesses
void GRExprEngine::VisitArraySubscriptExpr(ArraySubscriptExpr* A,
NodeTy* Pred,
NodeSet& Dst, bool
asLValue) {
Expr* Base = A->getBase()->IgnoreParens();
Expr* Idx = A->getIdx()->IgnoreParens();
NodeSet Tmp;
Visit(Base, Pred, Tmp); // Get Base's rvalue, which should be an
LocVal.
for (NodeSet::iterator I1=Tmp.begin(), E1=Tmp.end(); I1!=E1; ++I1) {
NodeSet Tmp2;
Visit(Idx, *I1, Tmp2); // Evaluate the index.
for (NodeSet::iterator I2=Tmp2.begin(), E2=Tmp2.end(); I2!=E2; +
+I2) {
const GRState* St = GetState(*I2);
// **** Possible insert a call to StoreManager::PointerToArray
here for the
// **** results of GetSVal(St, Base).
SVal V = StateMgr.GetLValue(St, GetSVal(St, Base), GetSVal(St,
Idx));
...
I'm not saying this is the best solution; it just seems that using an
ElementRegion early seems speculative and premature, especially if it
really isn't an array. Why not just do it lazily when a region is
*used* as an array?
Of course, this leads to the question of how we handle general pointer
arithmetic (one of those things we're basically punting on right now).
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