[cfe-dev] LValueExprEvaluator::VisitArraySubscriptExpr assertion

[Richard Smith]

On Wed, Mar 25, 2015 at 2:48 AM, Stephan Bergmann <sbergman at redhat.com>
wrote:

> In LibreOffice we have a Clang plugin calling Expr::EvaluateAsBooleanCondition,
> and at least with a recent trunk Clang build with assertions enabled that
> triggers the assert in
>
>  static bool EvaluatePointer(const Expr* E, LValue& Result, EvalInfo
>> &Info) {
>>   assert(E->isRValue() && E->getType()->hasPointerRepresentation());
>>   return PointerExprEvaluator(Info, Result).Visit(E);
>> }
>>
>
> (in lib/AST/ExprConstant.cpp) on expressions like
>
>   m_Strings[nEntry]
>
> where m_Strings is of std::vector type.
>
> What happens is that Expr::EvaluateAsBooleanCondition goes into
> LValueExprEvaluator::VisitArraySubscriptExpr, which calls
> EvaluatePointer, which asserts because m_Strings doesn't have array or
> pointer type.
>
> It's not clear to me where the error lies; should LValueExprEvaluator::VisitArraySubscriptExpr
> even be reached for uses of user-defined operator[] overloads?
>

No. Are you calling EvaluateAsBooleanCondition on a value-dependent
expression, perhaps? We should probably add an assert for that.


> For now, I'm working around the assertion with
>
>  Index: lib/AST/ExprConstant.cpp
>> ===================================================================
>> --- lib/AST/ExprConstant.cpp    (revision 233173)
>> +++ lib/AST/ExprConstant.cpp    (working copy)
>> @@ -4647,6 +4647,10 @@
>>    if (E->getBase()->getType()->isVectorType())
>>      return Error(E);
>>
>> +  if (!(E->getBase()->getType()->isArrayType() ||
>> +        E->getBase()->getType()->isPointerType()))
>> +    return false;
>> +
>>    if (!EvaluatePointer(E->getBase(), Result, Info))
>>      return false;
>>
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