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

[Richard Smith]

On Wed, Feb 15, 2012 at 11:46 AM, Matthieu Monrocq <
matthieu.monrocq at gmail.com> wrote:

> 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.
>

Yes, exactly so. Fixing the language > providing good warnings. :-)

- Richard
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