Re: [PATCH] c++: Attribute deprecated/unavailable divergence

[Jason Merrill <jason@redhat.com>]

On 3/2/22 14:31, Marek Polacek wrote:
> Attributes deprecated and unavailable are largely the same, except
> that the former produces a warning whereas the latter produces an error.
> So is_late_template_attribute should treat them the same.  Confirmed by
> Iain that this divergence is not intentional:
> <https://gcc.gnu.org/pipermail/gcc-patches/2022-February/591007.html>.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk or defer to GCC 13?

OK.

> gcc/cp/ChangeLog:
> 
> 	* decl2.cc (is_late_template_attribute): Do not defer attribute
> 	unavailable.
> 	* pt.cc (tsubst_enum): Set TREE_UNAVAILABLE.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/ext/attr-unavailable-9.C: Add dg-error.
> ---
>   gcc/cp/decl2.cc                               | 1 +
>   gcc/cp/pt.cc                                  | 4 +---
>   gcc/testsuite/g++.dg/ext/attr-unavailable-9.C | 4 ++--
>   3 files changed, 4 insertions(+), 5 deletions(-)
> 
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index 22edc2ba7f9..2752426546c 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -1314,6 +1314,7 @@ is_late_template_attribute (tree attr, tree decl)
>   	       /* But some attributes specifically apply to templates.  */
>   	       && !is_attribute_p ("abi_tag", name)
>   	       && !is_attribute_p ("deprecated", name)
> +	       && !is_attribute_p ("unavailable", name)
>   	       && !is_attribute_p ("visibility", name))
>   	return true;
>         else
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index 8fb17349ee1..853738410be 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -26976,9 +26976,7 @@ tsubst_enum (tree tag, tree newtag, tree args)
>     DECL_SOURCE_LOCATION (TYPE_NAME (newtag))
>       = DECL_SOURCE_LOCATION (TYPE_NAME (tag));
>     TREE_DEPRECATED (newtag) = TREE_DEPRECATED (tag);
> -  /* We don't need to propagate TREE_UNAVAILABLE here, because it is, unlike
> -     deprecated, applied at instantiation time rather than template
> -     definition time.  */
> +  TREE_UNAVAILABLE (newtag) = TREE_UNAVAILABLE (tag);
>   }
>   
>   /* DECL is a FUNCTION_DECL that is a template specialization.  Return
> diff --git a/gcc/testsuite/g++.dg/ext/attr-unavailable-9.C b/gcc/testsuite/g++.dg/ext/attr-unavailable-9.C
> index 44161336e78..6df55d534f8 100644
> --- a/gcc/testsuite/g++.dg/ext/attr-unavailable-9.C
> +++ b/gcc/testsuite/g++.dg/ext/attr-unavailable-9.C
> @@ -3,10 +3,10 @@
>   /* { dg-options "" } */
>   
>   template<typename T> struct __attribute__ ((unavailable)) S {};
> -S<int> s;
> +S<int> s;			// { dg-error "unavailable" }
>   
>   template <template <class> class T> struct A { };
> -A<S> a;
> +A<S> a;				// { dg-error "unavailable" }
>   
>   template <class T> void f() __attribute__ ((unavailable));
>   
> 
> base-commit: 8fede2876a751d53a28442dcca32466daa929daa