[cfe-commits] r150510 - in /cfe/trunk: include/clang/AST/Expr.h lib/AST/Expr.cpp lib/AST/ExprConstant.cpp test/SemaCXX/nullptr.cpp

[Matthieu Monrocq]

Le 14 février 2012 22:38, Richard Smith <richard-llvm at metafoo.co.uk> a
écrit :

> Author: rsmith
> Date: Tue Feb 14 15:38:30 2012
> New Revision: 150510
>
> URL: http://llvm.org/viewvc/llvm-project?rev=150510&view=rev
> Log:
> Pending clear answer from WG21 on whether core issue 903 is intended to
> apply to
> C++11 or just C++17, restrict the set of null pointer constants in C++11
> mode
> back to those which were considered null in C++98.
>
> Modified:
>    cfe/trunk/include/clang/AST/Expr.h
>    cfe/trunk/lib/AST/Expr.cpp
>    cfe/trunk/lib/AST/ExprConstant.cpp
>    cfe/trunk/test/SemaCXX/nullptr.cpp
>
> Modified: cfe/trunk/include/clang/AST/Expr.h
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Expr.h?rev=150510&r1=150509&r2=150510&view=diff
>
> ==============================================================================
> --- cfe/trunk/include/clang/AST/Expr.h (original)
> +++ cfe/trunk/include/clang/AST/Expr.h Tue Feb 14 15:38:30 2012
> @@ -423,6 +423,10 @@
>                              bool isEvaluated = true) const;
>   bool isIntegerConstantExpr(ASTContext &Ctx, SourceLocation *Loc = 0)
> const;
>
> +  /// isCXX98IntegralConstantExpr - Return true if this expression is an
> +  /// integral constant expression in C++98. Can only be used in C++.
> +  bool isCXX98IntegralConstantExpr(ASTContext &Ctx) const;
> +
>   /// isCXX11ConstantExpr - Return true if this expression is a constant
>   /// expression in C++11. Can only be used in C++.
>   ///
>
> Modified: cfe/trunk/lib/AST/Expr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=150510&r1=150509&r2=150510&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/Expr.cpp (original)
> +++ cfe/trunk/lib/AST/Expr.cpp Tue Feb 14 15:38:30 2012
> @@ -2728,11 +2728,18 @@
>     return NPCK_NotNull;
>
>   // If we have an integer constant expression, we need to *evaluate* it
> and
> -  // test for the value 0.
> -  llvm::APSInt Result;
> -  bool IsNull = isIntegerConstantExpr(Result, Ctx) && Result == 0;
> +  // test for the value 0. Don't use the C++11 constant expression
> semantics
> +  // for this, for now; once the dust settles on core issue 903, we might
> only
> +  // allow a literal 0 here in C++11 mode.
> +  if (Ctx.getLangOptions().CPlusPlus0x) {
> +    if (!isCXX98IntegralConstantExpr(Ctx))
> +      return NPCK_NotNull;
> +  } else {
> +    if (!isIntegerConstantExpr(Ctx))
> +      return NPCK_NotNull;
> +  }
>
> -  return (IsNull ? NPCK_ZeroInteger : NPCK_NotNull);
> +  return (EvaluateKnownConstInt(Ctx) == 0) ? NPCK_ZeroInteger :
> NPCK_NotNull;
>  }
>
>  /// \brief If this expression is an l-value for an Objective C
>
> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=150510&r1=150509&r2=150510&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
> +++ cfe/trunk/lib/AST/ExprConstant.cpp Tue Feb 14 15:38:30 2012
> @@ -6435,12 +6435,17 @@
>   return true;
>  }
>
> +bool Expr::isCXX98IntegralConstantExpr(ASTContext &Ctx) const {
> +  return CheckICE(this, Ctx).Val == 0;
> +}
> +
>  bool Expr::isCXX11ConstantExpr(ASTContext &Ctx, APValue *Result,
>                                SourceLocation *Loc) const {
>   // We support this checking in C++98 mode in order to diagnose
> compatibility
>   // issues.
>   assert(Ctx.getLangOptions().CPlusPlus);
>
> +  // Build evaluation settings.
>   Expr::EvalStatus Status;
>   llvm::SmallVector<PartialDiagnosticAt, 8> Diags;
>   Status.Diag = &Diags;
>
> Modified: cfe/trunk/test/SemaCXX/nullptr.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/nullptr.cpp?rev=150510&r1=150509&r2=150510&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/nullptr.cpp (original)
> +++ cfe/trunk/test/SemaCXX/nullptr.cpp Tue Feb 14 15:38:30 2012
> @@ -161,3 +161,14 @@
>
>   X2<nullptr, nullptr, nullptr, nullptr> x2;
>  }
> +
> +namespace null_pointer_constant {
> +
> +// Pending implementation of core issue 903, ensure we don't allow any of
> the
> +// C++11 constant evaluation semantics in null pointer constants.
> +struct S { int n; };
> +constexpr int null() { return 0; }
> +void *p = S().n; // expected-error {{cannot initialize}}
> +void *q = null(); // expected-error {{cannot initialize}}
> +
> +}
>
>
Just for my curiosity: is it the discrepancy between C++98 and C++11 that
Chandler mentionned you and he had discovered just right before GoingNative
2012 ? It really looks like it.

--Matthieu
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