[cfe-commits] [PATCH][MS][Review request] - Microsoft function specialization at scope scope

[Francois Pichet]

Thanks for the review, here is patch #2 with some changes:

On Fri, Jun 24, 2011 at 11:18 AM, Douglas Gregor <dgregor at apple.com> wrote:
>
> On Jun 16, 2011, at 6:26 PM, Francois Pichet wrote:
>
>
> Index: include/clang/Basic/DiagnosticSemaKinds.td
> ===================================================================
> --- include/clang/Basic/DiagnosticSemaKinds.td  (revision 133213)
> +++ include/clang/Basic/DiagnosticSemaKinds.td  (working copy)
> @@ -1867,6 +1867,9 @@
>
>   "explicit specialization of %0 in function scope">;
>  def err_template_spec_decl_class_scope : Error<
>   "explicit specialization of %0 in class scope">;
> +def warn_template_spec_decl_class_scope : ExtWarn<
> +  "explicit specialization of %0 in class scope in a Microsoft extension">,
> +  InGroup<Microsoft>;
>
> This should say "is a Microsoft extension".

Done

>
> Index: lib/Sema/SemaDecl.cpp
> ===================================================================
> --- lib/Sema/SemaDecl.cpp       (revision 133213)
> +++ lib/Sema/SemaDecl.cpp       (working copy)
> @@ -1688,9 +1688,13 @@
>
>       // Preserve triviality.
>       NewMethod->setTrivial(OldMethod->isTrivial());
>
> +      // MSVC allows explicit template specialization at class scope.
> +      bool IsMSExplicitSpecialization = getLangOptions().Microsoft &&
> +                                 NewMethod->isFunctionTemplateSpecialization();
>       bool isFriend = NewMethod->getFriendObjectKind();
>
> -      if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord()) {
> +      if (!isFriend && NewMethod->getLexicalDeclContext()->isRecord() &&
> +          !IsMSExplicitSpecialization) {
>         //    -- Member function declarations with the same name and the
>         //       same parameter types cannot be overloaded if any of them
>         //       is a static member function declaration.
> @@ -4649,6 +4653,17 @@
>
>     } else if (isFunctionTemplateSpecialization) {
>       if (CurContext->isDependentContext() && CurContext->isRecord()
>           && !isFriend) {
> +        if (getLangOptions().Microsoft) {
> +          ClassScopeFunctionSpecializationDecl *NewSpec =
> +                               ClassScopeFunctionSpecializationDecl::Create(
> +                                      Context, CurContext,  SourceLocation(),
> +                                      cast<CXXMethodDecl>(NewFD));
> +          CurContext->addDecl(NewSpec);
> +          Redeclaration = true;
> +          NewFD->setInvalidDecl();
> +          return NewFD;
> +        }
> +
>         Diag(NewFD->getLocation(), diag::err_function_specialization_in_class)
>           << NewFD->getDeclName();
>         NewFD->setInvalidDecl();
>
> We shouldn't perform an early-exit here, because it means that we're missing out on a lot of semantic analysis, such as adding attributes and checking the qualification. Can we just make a note that this is a class-scope function specialization, do all of the extra checking, and then build the ClassScopeFunctionSpecializationDecl at the end?
>
> Also, I think it'd be cleaner if we always used ClassScopeFunctionSpecializationDecl to handle class-scope function specializations, regardless of whether we're in Microsoft mode. It would be great if the only check for getLangOptions().Microsoft was to decide whether to emit the ExtWarn vs. the Error. Plus, we'll get better testing coverage that way :)
>

Ok done too.

> Index: lib/Sema/SemaTemplateInstantiateDecl.cpp
> ===================================================================
> --- lib/Sema/SemaTemplateInstantiateDecl.cpp    (revision 133213)
> +++ lib/Sema/SemaTemplateInstantiateDecl.cpp    (working copy)
> @@ -1890,6 +1890,89 @@
>
>   return UD;
>  }
>
> +Decl *TemplateDeclInstantiator::VisitClassScopeFunctionSpecializationDecl(
> +                                     ClassScopeFunctionSpecializationDecl *Decl) {
>
> There's a lot of redundancy between this method and TemplateDeclInstantiator::VisitCXXMethodDecl(). Did you try passing additional state to VisitCXXMethodDecl, so that we can re-use (and tweak) the code there rather than copying most of the code?
>
> This part in particular confuses me:
>
> +
> +  // Instantiate NewFD.
> +  SemaRef.InstantiateFunctionDefinition(SourceLocation(), NewFD, false,
> +                                        false, false);
>
> Why are we instantiating the function definition? We shouldn't need to do that.
>

Ok I removed the duplication and added a flag to VisitCXXMethodDecl.
This patch is different in that the instantiation is now done properly
at the end of the translation unit like any others.
This add some small complexity (some
getClassScopeSpecializationPattern checking here and there) to not
bail out because we are dealing with a TSK_ExplicitSpecialization at
instantiation time.

Also one potentially controversial aspect of this patch is that it
adds a new pointer (ClassScopeSpecializationPattern) to the
FunctionTemplateSpecializationInfo class. This new pointer is used to
retrieved the function pattern during the instantiation of a class
scope explicit specialization. So there is a 4-byte added for a rarely
used feature. Not sure if that's acceptable.


Thanks again,
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