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[PATCH v10 25/28] gnu directives: add support for .gnu_attribute and .gnu_subsection in OAv2 context

Jan Beulich jbeulich@suse.com
Fri Dec 19 09:08:34 GMT 2025 
On 20.11.2025 18:59, Matthieu Longo wrote:
> --- a/bfd/elf-attrs.c
> +++ b/bfd/elf-attrs.c
> @@ -605,12 +605,13 @@ obj_attr_subsection_scope_v2_t
>  bfd_elf_obj_attr_subsection_v2_scope (const bfd *abfd, const char *subsec_name)
>  {
>    const char *vendor_name = get_elf_backend_data (abfd)->obj_attrs_vendor;
> +  obj_attr_subsection_scope_v2_t scope = OA_SUBSEC_PRIVATE;
>    size_t vendor_name_len = strlen (vendor_name);
> -  obj_attr_subsection_scope_v2_t scope
> -    = (strncmp (subsec_name, vendor_name, vendor_name_len) == 0
> -       && subsec_name[vendor_name_len] == '_'
> -       ? OA_SUBSEC_PUBLIC
> -       : OA_SUBSEC_PRIVATE);
> +  if ((strncmp (subsec_name, vendor_name, vendor_name_len) == 0
> +       && subsec_name[vendor_name_len] == '_')
> +      || (strncmp (subsec_name, "gnu_", 4) == 0
> +	  && !gnu_testing_namespace (subsec_name)))
> +    scope = OA_SUBSEC_PUBLIC;
>    return scope;
>  }

Please have this change focus on what is actually in need of changing. I.e.
either stick to using a conditional expression, or avoid use of one right
when the function is first introduced. There really is no value in such
extra churn.

> --- a/gas/config/obj-elf-attr.c
> +++ b/gas/config/obj-elf-attr.c
> @@ -1272,4 +1272,38 @@ obj_elf_gnu_attribute (int ignored ATTRIBUTE_UNUSED)
>    obj_attr_process_attribute (OBJ_ATTR_GNU);
>  }
>  
> +#if (TC_OBJ_ATTR_v2)
> +/* Return True if the VERSION of object attributes supports subsections, False
> +   otherwise.  */
> +
> +static inline bool
> +attr_fmt_has_subsections (obj_attr_version_t version)
> +{
> +  switch (version)
> +  {
> +  case OBJ_ATTR_V1:
> +    return false;
> +  case OBJ_ATTR_V2:
> +    return true;
> +  default:
> +    abort ();  /* Unsupported format.  */
> +  }

Is it really guaranteed that OBJ_ATTR_VERSION_NONE and OBJ_ATTR_VERSION_UNSUPPORTED
can't make it here, e.g. ...

> +}
> +
> +/* Parse a .gnu_subsection directive.  */
> +
> +void
> +obj_elf_gnu_subsection (int ignored ATTRIBUTE_UNUSED)
> +{
> +  obj_attr_version_t version = elf_obj_attr_version (stdoutput);
> +  if (! attr_fmt_has_subsections (version))

... when coming from here? Patch 05 sets it from ->default_obj_attr_version,
but what is unclear to me is whether that default setting can't later be
overridden. After all the comment there only says "recommended".

Jan
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