r211568 - AST: Address of dllimport variables isn't constant

[David Majnemer]

That code isn't representative of what's in ToT at this point.  We now have
a check for dllimport in CheckLValueConstantExpression.


On Fri, Jun 27, 2014 at 8:34 AM, Richard Smith <richard at metafoo.co.uk>
wrote:

> On Mon, Jun 23, 2014 at 10:59 PM, David Majnemer <david.majnemer at gmail.com
> > wrote:
>
>> Author: majnemer
>> Date: Tue Jun 24 00:59:13 2014
>> New Revision: 211568
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=211568&view=rev
>> Log:
>> AST: Address of dllimport variables isn't constant
>>
>> The address of dllimport variables isn't something that can be
>> meaningfully used in a constexpr context and isn't suitable for
>> evaluation at load-time.  They require loads from memory to properly
>> evaluate.
>>
>> This fixes PR19955.
>>
>> Differential Revision: http://reviews.llvm.org/D4250
>>
>> Added:
>>     cfe/trunk/test/CodeGenCXX/PR19955.cpp
>>     cfe/trunk/test/SemaCXX/PR19955.cpp
>> Modified:
>>     cfe/trunk/lib/AST/ExprConstant.cpp
>>
>> Modified: cfe/trunk/lib/AST/ExprConstant.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/ExprConstant.cpp?rev=211568&r1=211567&r2=211568&view=diff
>>
>> ==============================================================================
>> --- cfe/trunk/lib/AST/ExprConstant.cpp (original)
>> +++ cfe/trunk/lib/AST/ExprConstant.cpp Tue Jun 24 00:59:13 2014
>> @@ -4390,6 +4390,9 @@ bool LValueExprEvaluator::VisitVarDecl(c
>>        Result.set(VD, Frame->Index);
>>        return true;
>>      }
>> +    // The address of __declspec(dllimport) variables aren't constant.
>> +    if (VD->hasAttr<DLLImportAttr>())
>> +      return ZeroInitialization(E);
>>
>
> This seems weird; there is no such thing as zero-initialization of an
> lvalue. Just use 'Error(E)' instead? (Or, better, provide a note explaining
> why it's non-constant.)
>
>      return Success(VD);
>>    }
>>
>>
>> Added: cfe/trunk/test/CodeGenCXX/PR19955.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/PR19955.cpp?rev=211568&view=auto
>>
>> ==============================================================================
>> --- cfe/trunk/test/CodeGenCXX/PR19955.cpp (added)
>> +++ cfe/trunk/test/CodeGenCXX/PR19955.cpp Tue Jun 24 00:59:13 2014
>> @@ -0,0 +1,10 @@
>> +// RUN: %clang_cc1 -triple i686-windows-msvc -fno-rtti -emit-llvm
>> -std=c++1y -O0 -o - %s | FileCheck %s
>> +// RUN: %clang_cc1 -triple x86_64-windows-msvc -fno-rtti -emit-llvm
>> -std=c++1y -O0 -o - %s | FileCheck %s
>> +
>> +extern int __declspec(dllimport) x;
>> +extern long long y;
>> +// CHECK-DAG: @"\01?y@@3_JA" = global i64 0
>> +long long y = (long long)&x;
>> +
>> +// CHECK-LABEL: @"\01??__Ey@@YAXXZ"
>> +// CHECK-DAG: @"\01?y@@3_JA"
>>
>> Added: cfe/trunk/test/SemaCXX/PR19955.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/PR19955.cpp?rev=211568&view=auto
>>
>> ==============================================================================
>> --- cfe/trunk/test/SemaCXX/PR19955.cpp (added)
>> +++ cfe/trunk/test/SemaCXX/PR19955.cpp Tue Jun 24 00:59:13 2014
>> @@ -0,0 +1,4 @@
>> +// RUN: %clang_cc1 -triple i686-win32 -verify -std=c++11 %s
>> +
>> +extern int __attribute__((dllimport)) y;
>> +constexpr int *x = &y; // expected-error {{must be initialized by a
>> constant expression}}
>>
>>
>> _______________________________________________
>> cfe-commits mailing list
>> cfe-commits at cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-commits
>>
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-commits/attachments/20140627/dfe9dfa7/attachment.html>