Re: [PATCH] c++, abi: Fix abi_tag attribute handling [PR98481]

[Jakub Jelinek <jakub@redhat.com>]

On Fri, Jan 08, 2021 at 02:22:59PM -0500, Jason Merrill wrote:
> I like the idea to use *walk_subtrees to distinguish between walking
> syntactic subtrees and walking type-identity subtrees.  But it should be
> more general; how does this look to you?

LGTM, thanks.

> diff --git a/gcc/cp/class.c b/gcc/cp/class.c
> index c41ac7deefe..00c0dba0a55 100644
> --- a/gcc/cp/class.c
> +++ b/gcc/cp/class.c
> @@ -1507,6 +1507,10 @@ mark_or_check_tags (tree t, tree *tp, abi_tag_data *p, bool val)
>  static tree
>  find_abi_tags_r (tree *tp, int *walk_subtrees, void *data)
>  {
> +  if (TYPE_P (*tp) && *walk_subtrees == 1)
> +    /* Tell cp_walk_subtrees to look though typedefs.  */
> +    *walk_subtrees = 2;
> +
>    if (!OVERLOAD_TYPE_P (*tp))
>      return NULL_TREE;
>  
> @@ -1527,6 +1531,10 @@ find_abi_tags_r (tree *tp, int *walk_subtrees, void *data)
>  static tree
>  mark_abi_tags_r (tree *tp, int *walk_subtrees, void *data)
>  {
> +  if (TYPE_P (*tp) && *walk_subtrees == 1)
> +    /* Tell cp_walk_subtrees to look though typedefs.  */
> +    *walk_subtrees = 2;
> +
>    if (!OVERLOAD_TYPE_P (*tp))
>      return NULL_TREE;
>  
> diff --git a/gcc/cp/decl2.c b/gcc/cp/decl2.c
> index b10671091b5..b087753cfba 100644
> --- a/gcc/cp/decl2.c
> +++ b/gcc/cp/decl2.c
> @@ -2358,9 +2358,6 @@ min_vis_r (tree *tp, int *walk_subtrees, void *data)
>    int this_vis = VISIBILITY_DEFAULT;
>    if (! TYPE_P (*tp))
>      *walk_subtrees = 0;
> -  else if (typedef_variant_p (*tp))
> -    /* Look through typedefs despite cp_walk_subtrees.  */
> -    this_vis = type_visibility (DECL_ORIGINAL_TYPE (TYPE_NAME (*tp)));
>    else if (OVERLOAD_TYPE_P (*tp)
>  	   && !TREE_PUBLIC (TYPE_MAIN_DECL (*tp)))
>      {
> @@ -2379,6 +2376,10 @@ min_vis_r (tree *tp, int *walk_subtrees, void *data)
>    if (this_vis > *vis_p)
>      *vis_p = this_vis;
>  
> +  /* Tell cp_walk_subtrees to look through typedefs.  */
> +  if (*walk_subtrees == 1)
> +    *walk_subtrees = 2;
> +
>    return NULL;
>  }
>  
> diff --git a/gcc/cp/tree.c b/gcc/cp/tree.c
> index 82027cc9abf..c536eb581a7 100644
> --- a/gcc/cp/tree.c
> +++ b/gcc/cp/tree.c
> @@ -5146,16 +5146,26 @@ cp_walk_subtrees (tree *tp, int *walk_subtrees_p, walk_tree_fn func,
>  
>    if (TYPE_P (*tp))
>      {
> -      /* Walk into template args without looking through typedefs.  */
> -      if (tree ti = TYPE_TEMPLATE_INFO_MAYBE_ALIAS (*tp))
> -	WALK_SUBTREE (TI_ARGS (ti));
> -      /* Don't look through typedefs; walk_tree_fns that want to look through
> -	 typedefs (like min_vis_r) need to do that themselves.  */
> -      if (typedef_variant_p (*tp))
> +      /* If *WALK_SUBTREES_P is 1, we're interested in the syntactic form of
> +	 the argument, so don't look through typedefs, but do walk into
> +	 template arguments for alias templates (and non-typedefed classes).
> +
> +	 If *WALK_SUBTREES_P > 1, we're interested in type identity or
> +	 equivalence, so look through typedefs, ignoring template arguments for
> +	 alias templates, and walk into template args of classes.
> +
> +	 See find_abi_tags_r for an example of setting *WALK_SUBTREES_P to 2
> +	 when that's the behavior the walk_tree_fn wants.  */
> +      if (*walk_subtrees_p == 1 && typedef_variant_p (*tp))
>  	{
> +	  if (tree ti = TYPE_ALIAS_TEMPLATE_INFO (*tp))
> +	    WALK_SUBTREE (TI_ARGS (ti));
>  	  *walk_subtrees_p = 0;
>  	  return NULL_TREE;
>  	}
> +
> +      if (tree ti = TYPE_TEMPLATE_INFO (*tp))
> +	WALK_SUBTREE (TI_ARGS (ti));
>      }
>  
>    /* Not one of the easy cases.  We must explicitly go through the


	Jakub