[PATCH] PR63300 'const volatile' sometimes stripped in debug info.

Mark Wielaard mjw@redhat.com
Tue Sep 23 14:56:00 GMT 2014


On Tue, 2014-09-23 at 14:17 +0200, Andreas Arnez wrote:
> > Also note that the logic wouldn't scale too well for yet more
> > qualifiers...
> 
> Considering this, I've tried a different approach below.  What do you
> think?

Having support in tree.c instead of doing it by hand in dwarf2out.c is
certainly nice.

> -- >8 --
> Subject: [PATCH] PR63300 'const volatile' sometimes stripped in debug info.
> 
> When adding DW_TAG_restrict_type the handling of multiple modifiers
> was adjusted incorrectly.  This patch fixes it with the help of a new
> tree function get_nearest_type_subqualifiers.
> 
> gcc/ChangeLog
> 
> 	* tree.c (check_base_type): New.
> 	(check_qualified_type): Exploit new helper function above.
> 	(get_nearest_type_subqualifiers): New.
> 	* tree.h (get_nearest_type_subqualifiers): New prototype.
> 	* dwarf2out.c (modified_type_die): Fix handling for qualifiers.
> 	Next qualifier to "peel off" is now determined with the help of
> 	get_nearest_type_subqualifiers.

> +  if (cv_quals)
> +    {
> +      int q;
> +      enum dwarf_tag t;
> +
> +      q = get_nearest_type_subqualifiers (type, cv_quals, cv_qual_mask);
> +      q = cv_quals & ~q;
> +
> +      if (q & TYPE_QUAL_CONST)
> +	{
> +	  q = TYPE_QUAL_CONST;
> +	  t = DW_TAG_const_type;
> +	}
> +      else if (q & TYPE_QUAL_VOLATILE)
> +	{
> +	  q = TYPE_QUAL_VOLATILE;
> +	  t = DW_TAG_volatile_type;
> +	}
> +      else
> +	{
> +	  q = TYPE_QUAL_RESTRICT;
> +	  t = DW_TAG_restrict_type;
> +	}
>
> +      mod_type_die = new_die (t, mod_scope, type);
> +      sub_die = modified_type_die (type, cv_quals & ~q, context_die);

This certainly looks nicer than how I wrote it. It took me a while
(again) to realize why this works. We rely on the fact that earlier in
the function a match would have been found if there was already a fully
qualified type available. So here we know some subset will be found and
at least one qualifier we need will not be in the result returned by
get_nearest_type_subqualifiers. Maybe add a comment saying that to the
code?

Could you add the testcases I wrote for my variant of the fix to your
patch and make sure they PASS?

Thanks,

Mark



More information about the Gcc-patches mailing list