Re: [PATCH] c++: init_priority and SUPPORTS_INIT_PRIORITY [PR107638]

[Jason Merrill <jason@redhat.com>]

On 11/11/22 08:47, Patrick Palka wrote:
> The commit r13-3706-gd0a492faa6478c for correcting the result of
> __has_attribute(init_priority) causes a bootstrap failure on hppa64-hpux
> because it assumes SUPPORTS_INIT_PRIORITY expands to a simple constant,
> but on this target SUPPORTS_INIT_PRIORITY is defined as
> 
>    #define SUPPORTS_INIT_PRIORITY (TARGET_GNU_LD ? 1 : 0)
> 
> (where TARGET_GNU_LD expands to something in terms of global_options)
> which means we can't use this macro to statically exclude the entry
> for init_priority when defining the cxx_attribute_table.
> 
> So instead of trying to exclude init_priority from the attribute table
> for sake of __has_attribute, this patch just makes __has_attribute
> handle init_priority specially.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?  Also sanity checked by artificially defining SUPPORTS_INIT_PRIORITY
> to 0.

OK.

> 	PR c++/107638
> 
> gcc/c-family/ChangeLog:
> 
> 	* c-lex.cc (c_common_has_attribute): Return 1 for init_priority
> 	iff SUPPORTS_INIT_PRIORITY.
> 
> gcc/cp/ChangeLog:
> 
> 	* tree.cc (cxx_attribute_table): Don't conditionally exclude
> 	the init_priority entry.
> 	(handle_init_priority_attribute): Remove ATTRIBUTE_UNUSED.
> 	Return error_mark_node if !SUPPORTS_INIT_PRIORITY.
> ---
>   gcc/c-family/c-lex.cc |  9 +++++++++
>   gcc/cp/tree.cc        | 11 +++++++----
>   2 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/gcc/c-family/c-lex.cc b/gcc/c-family/c-lex.cc
> index 89c65aca28a..2fe562c7ccf 100644
> --- a/gcc/c-family/c-lex.cc
> +++ b/gcc/c-family/c-lex.cc
> @@ -380,6 +380,15 @@ c_common_has_attribute (cpp_reader *pfile, bool std_syntax)
>   		result = 201907;
>   	      else if (is_attribute_p ("assume", attr_name))
>   		result = 202207;
> +	      else if (is_attribute_p ("init_priority", attr_name))
> +		{
> +		  /* The (non-standard) init_priority attribute is always
> +		     included in the attribute table, but we don't want to
> +		     advertise the attribute unless the target actually
> +		     supports init priorities.  */
> +		  result = SUPPORTS_INIT_PRIORITY ? 1 : 0;
> +		  attr_name = NULL_TREE;
> +		}
>   	    }
>   	  else
>   	    {
> diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
> index c30bbeb0839..2324c2269fc 100644
> --- a/gcc/cp/tree.cc
> +++ b/gcc/cp/tree.cc
> @@ -5010,10 +5010,8 @@ const struct attribute_spec cxx_attribute_table[] =
>   {
>     /* { name, min_len, max_len, decl_req, type_req, fn_type_req,
>          affects_type_identity, handler, exclude } */
> -#if SUPPORTS_INIT_PRIORITY
>     { "init_priority",  1, 1, true,  false, false, false,
>       handle_init_priority_attribute, NULL },
> -#endif
>     { "abi_tag", 1, -1, false, false, false, true,
>       handle_abi_tag_attribute, NULL },
>     { NULL, 0, 0, false, false, false, false, NULL, NULL }
> @@ -5041,13 +5039,19 @@ const struct attribute_spec std_attribute_table[] =
>   
>   /* Handle an "init_priority" attribute; arguments as in
>      struct attribute_spec.handler.  */
> -ATTRIBUTE_UNUSED static tree
> +static tree
>   handle_init_priority_attribute (tree* node,
>   				tree name,
>   				tree args,
>   				int /*flags*/,
>   				bool* no_add_attrs)
>   {
> +  if (!SUPPORTS_INIT_PRIORITY)
> +    /* Treat init_priority as an unrecognized attribute (mirroring the
> +       result of __has_attribute) if the target doesn't support init
> +       priorities.  */
> +    return error_mark_node;
> +
>     tree initp_expr = TREE_VALUE (args);
>     tree decl = *node;
>     tree type = TREE_TYPE (decl);
> @@ -5105,7 +5109,6 @@ handle_init_priority_attribute (tree* node,
>   	 pri);
>       }
>   
> -  gcc_assert (SUPPORTS_INIT_PRIORITY);
>     SET_DECL_INIT_PRIORITY (decl, pri);
>     DECL_HAS_INIT_PRIORITY_P (decl) = 1;
>     return NULL_TREE;