r244488 - [dllimport] A non-imported class with an imported key can't have a key

[Richard Smith via cfe-commits]

On Mon, Aug 10, 2015 at 12:39 PM, Reid Kleckner via cfe-commits <
cfe-commits at lists.llvm.org> wrote:

> Author: rnk
> Date: Mon Aug 10 14:39:01 2015
> New Revision: 244488
>
> URL: http://llvm.org/viewvc/llvm-project?rev=244488&view=rev
> Log:
> [dllimport] A non-imported class with an imported key can't have a key
>
> Summary:
> The vtable takes its DLL storage class from the class, not the key
> function. When they disagree, the vtable won't be exported by the DLL
> that defines the key function. The easiest way to ensure that importers
> of the class emit their own vtable is to say that the class has no key
> function.
>
> Reviewers: hans, majnemer
>
> Subscribers: cfe-commits
>
> Differential Revision: http://reviews.llvm.org/D11913
>
> Modified:
>     cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
>     cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp
>
> Modified: cfe/trunk/lib/AST/RecordLayoutBuilder.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/RecordLayoutBuilder.cpp?rev=244488&r1=244487&r2=244488&view=diff
>
> ==============================================================================
> --- cfe/trunk/lib/AST/RecordLayoutBuilder.cpp (original)
> +++ cfe/trunk/lib/AST/RecordLayoutBuilder.cpp Mon Aug 10 14:39:01 2015
> @@ -2008,6 +2008,12 @@ static const CXXMethodDecl *computeKeyFu
>          continue;
>      }
>
> +    // If the key function is dllimport but the class isn't, then the
> class has
> +    // no key function. The DLL that exports the key function won't
> export the
> +    // vtable in this case.
> +    if (MD->hasAttr<DLLImportAttr>() && !RD->hasAttr<DLLImportAttr>())
> +      return nullptr;
>

Does the same apply if the key function is DLLExport and the class is not?
(Presumably this would just lead us to export a vtable that we don't need
to, which is presumably harmless?)


> +
>      // We found it.
>      return MD;
>    }
>
> Modified: cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp?rev=244488&r1=244487&r2=244488&view=diff
>
> ==============================================================================
> --- cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp (original)
> +++ cfe/trunk/test/CodeGenCXX/dllimport-rtti.cpp Mon Aug 10 14:39:01 2015
> @@ -22,3 +22,11 @@ struct __declspec(dllimport) V {
>  // GNU-DAG: @_ZTV1V = available_externally dllimport
>  // GNU-DAG: @_ZTS1V = linkonce_odr
>  // GNU-DAG: @_ZTI1V = linkonce_odr
> +
> +struct W {
> +  __declspec(dllimport) virtual void f();
> +  virtual void g();
> +} w;
> +// GNU-DAG: @_ZTV1W = linkonce_odr
> +// GNU-DAG: @_ZTS1W = linkonce_odr
> +// GNU-DAG: @_ZTI1W = linkonce_odr
>
>
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