[cfe-dev] Local typedefs in templates

[Alex L via cfe-dev]

Hi,

I have observed something slightly different - both the dependent and
non-dependent non-instantiated TypedefDecl are marked as referenced (ToT
clang). It seems to me that you could try fixing the issue by marking the
instantiated TypedefDecls as referenced if the non-instantiated is
referenced (see TemplateDeclInstantiator::InstantiateTypedefNameDecl).

Alex

On 12 April 2017 at 08:29, Johannes Altmanninger via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> Hi,
>
> I have been working on fixing [1]. To me it is not obvious what is the
> proper solution is. Maybe someone has an idea?
>
> Consider this small test program:
>
> template <class T>
> void Function(T) {
>   struct Struct {
>     typedef int Something;
>     Something x;
>   };
> }
> void test() { Function('c'); }
>
> Compiling it with -Wall -fsyntax-only generates the warning about the
> local typedef being unused.
>
> When adding -ast-dump one can see that there are two TypedefDecls, one
> for the FunctionTemplateDecl and another for the one instantiation of
> the template. The same thing applies when the typedef is dependent on a
> template parameter, say "typedef T Something" in this case.
>
> I observed this behaviour:
>
> When the typedef is independent, then neither of the TypedefDecls will
> be marked referenced as of now. Additionally, the type of ValueDecls
> like "Something x;" has the non-templated typedef as its declaration.
>
> When the typedef is dependent, then only the non-templated TypedefDecl
> will be marked referenced. The type of ValueDecls does naturally refer
> to the instantiated TypedefDecl.
>
> Is it supposed to be that way?
>
> If the types of declarations always referred to the instantiated
> typedefs, it would be straightforward to fix by traversing all
> declarations and marking the typedefs of their types referenced.
>
> Alternatively, it would be possible to only check non-instantiated
> types on being referenced. Actually, this might to be the simplest one..
>
>
> Johannes
>
>
> [1] https://bugs.llvm.org/show_bug.cgi?id=24883
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20170412/3018648e/attachment.html>