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

[Tom Stellard via cfe-commits]

On 03/08/2018 06:03 PM, Richard Smith wrote:
> Might be a good candidate for Clang 6.0.1.
> 

Merge request created: https://llvm.org/PR36655

-Tom

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