r201468 - [Sema] Fix assertion hit while trying to do constant evaluation for a dependent expression

[Richard Smith]

On Sat, Feb 15, 2014 at 10:53 AM, Argyrios Kyrtzidis <akyrtzi at gmail.com>wrote:

> Author: akirtzidis
> Date: Sat Feb 15 12:53:57 2014
> New Revision: 201468
>
> URL: http://llvm.org/viewvc/llvm-project?rev=201468&view=rev
> Log:
> [Sema] Fix assertion hit while trying to do constant evaluation for a
> dependent expression
> inside a GNU statement expression.
>
> rdar://16064952
>
> Modified:
>     cfe/trunk/lib/AST/ExprConstant.cpp
>     cfe/trunk/test/SemaCXX/constant-expression.cpp
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=201468&r1=201467&r2=201468&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Sat Feb 15 12:53:57 2014
> @@ -8028,6 +8028,8 @@ static bool Evaluate(APValue &Result, Ev
>  /// an object can indirectly refer to subobjects which were initialized
> earlier.
>  static bool EvaluateInPlace(APValue &Result, EvalInfo &Info, const LValue
> &This,
>                              const Expr *E, bool AllowNonLiteralTypes) {
> +  if (E->isTypeDependent() || E->isValueDependent())
> +    return false;
>

It's the responsibility of the caller of the evaluator to check that the
expression isn't value-dependent, not of the evaluator itself (the answer
in such a case isn't that the expression is non-constant, it's that the
question isn't meaningful). This should be an assert, and the check should
be elsewhere. (Also, checking isValueDependent should be sufficient.)

   if (!AllowNonLiteralTypes && !CheckLiteralType(Info, E, &This))
>      return false;
>
>
> Modified: cfe/trunk/test/SemaCXX/constant-expression.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/constant-expression.cpp?rev=201468&r1=201467&r2=201468&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/constant-expression.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constant-expression.cpp Sat Feb 15 12:53:57 2014
> @@ -133,3 +133,11 @@ namespace test4 {
>    // equivalent to "const int x = 42;" as per C++03 8.5/p13.
>    typedef A<i> Ai; // ok
>  }
> +
> +// rdar://16064952
> +namespace rdar16064952 {
> +  template < typename T > void fn1() {
> +   T b;
> +   unsigned w = ({int a = b.val[sizeof(0)]; 0; }); // expected-warning
> {{use of GNU statement expression extension}}
> +  }
> +}
>
>
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