On Wed, Jan 08, 2025 at 02:35:56PM +0100, Mark Wielaard wrote:
> > --- gcc/dwarf2out.cc.jj 2025-01-02 11:23:35.541251268 +0100
> > +++ gcc/dwarf2out.cc 2025-01-07 10:09:16.866866563 +0100
> > @@ -8755,6 +8755,14 @@ break_out_comdat_types (dw_die_ref die)
> > unit = new_die (DW_TAG_type_unit, NULL, NULL);
> > add_AT_unsigned (unit, DW_AT_language,
> > get_AT_unsigned (comp_unit_die (),
> > DW_AT_language));
> > + if (unsigned lname = get_AT_unsigned (comp_unit_die (),
> > + DW_AT_language_name))
> > + {
> > + add_AT_unsigned (unit, DW_AT_language_name, lname);
> > + add_AT_unsigned (unit, DW_AT_language_version,
> > + get_AT_unsigned (comp_unit_die (),
> > + DW_AT_language_version));
> > + }
>
> This relies on language_name and language_version always being set
> together. Which is the case in the code at this time. Should we assert
> that?
Worst case it will emit the useless 0 in there.
I think we should never emit DW_AT_language_version without
DW_AT_language_name, but the other way around is possible, although
only at DWARF 6 time for languages which don't care about version.
For DWARF 5 we wouldn't bother with DW_AT_language_name in that case
and just emit DW_AT_language.
> The use of language_string (lang_hooks.name) is a little clumsy, but
> already part of the current code. In the future it would be nice to
> have separate language and version hooks for this.
The advantage of that is that it also shows up in human readable form
in DW_AT_producer that way.
> Personally I would just go with the new DW_LANG_C17/C23 language code,
> they will be supported by consumers when gcc 15 is released.
As discussed, I don't think that is a good idea, because some people won't
update all the tools and just use a newer gcc. And the advantages of
DW_LANG_C23/DW_LANG_C_plus_plus17 definitely don't outweight the pain if
using older tools (where debugging becomes really clumsy).
> The 00 for the month in C2Y is clever. Does that match the
> __STDC_VERSION__ defined?
Yes.
> Why 202400 and not 202600?
Because that is what __cplusplus is defined to for C++26 right now.
Newer than 202302 and 00 month indicates that it is just a temporary thing.
Jakub
