r327099 - PR36645: Go looking for an appropriate array bound when constant-evaluating a

[Richard Smith via cfe-commits]

Might be a good candidate for Clang 6.0.1.

On 8 March 2018 at 18:00, Richard Smith via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: rsmith
> Date: Thu Mar  8 18:00:01 2018
> New Revision: 327099
>
> URL: http://llvm.org/viewvc/llvm-project?rev=327099&view=rev
> Log:
> PR36645: Go looking for an appropriate array bound when
> constant-evaluating a
> name of an array object.
>
> Modified:
>     cfe/trunk/lib/AST/ExprConstant.cpp
>     cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/
> ExprConstant.cpp?rev=327099&r1=327098&r2=327099&view=diff
> ============================================================
> ==================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Thu Mar  8 18:00:01 2018
> @@ -63,14 +63,22 @@ namespace {
>
>    static QualType getType(APValue::LValueBase B) {
>      if (!B) return QualType();
> -    if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>())
> +    if (const ValueDecl *D = B.dyn_cast<const ValueDecl*>()) {
>        // FIXME: It's unclear where we're supposed to take the type from,
> and
> -      // this actually matters for arrays of unknown bound. Using the
> type of
> -      // the most recent declaration isn't clearly correct in general. Eg:
> +      // this actually matters for arrays of unknown bound. Eg:
>        //
>        // extern int arr[]; void f() { extern int arr[3]; };
>        // constexpr int *p = &arr[1]; // valid?
> -      return cast<ValueDecl>(D->getMostRecentDecl())->getType();
> +      //
> +      // For now, we take the array bound from the most recent
> declaration.
> +      for (auto *Redecl = cast<ValueDecl>(D->getMostRecentDecl());
> Redecl;
> +           Redecl = cast_or_null<ValueDecl>(Redecl->getPreviousDecl())) {
> +        QualType T = Redecl->getType();
> +        if (!T->isIncompleteArrayType())
> +          return T;
> +      }
> +      return D->getType();
> +    }
>
>      const Expr *Base = B.get<const Expr*>();
>
>
> Modified: cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/
> SemaCXX/constant-expression-cxx11.cpp?rev=327099&r1=
> 327098&r2=327099&view=diff
> ============================================================
> ==================
> --- cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp (original)
> +++ cfe/trunk/test/SemaCXX/constant-expression-cxx11.cpp Thu Mar  8
> 18:00:01 2018
> @@ -629,6 +629,10 @@ namespace ArrayOfUnknownBound {
>
>    extern const int carr[]; // expected-note {{here}}
>    constexpr int n = carr[0]; // expected-error {{constant}} expected-note
> {{non-constexpr variable}}
> +
> +  constexpr int local_extern[] = {1, 2, 3};
> +  void f() { extern const int local_extern[]; }
> +  static_assert(local_extern[1] == 2, "");
>  }
>
>  namespace DependentValues {
>
>
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