http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53880
--- Comment #16 from dodji at seketeli dot org <dodji at seketeli dot org> 2012-07-26 17:15:15 UTC --- "rguenth at gcc dot gnu.org" <gcc-bugzi...@gcc.gnu.org> a écrit: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53880 > > --- Comment #10 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-07-24 > 09:34:21 UTC --- > Err, isn't the GTY annotation in > > as y1. x0 is the spelling location for the argument token "1", > and x2 is the spelling location for the argument token "2". */ > source_location * GTY((length ("2 * %h.n_tokens"))) macro_locations; > > simply pointless? In theory, I would say yes it should be pointless. But in practise, it looks like the "gengtype code output system" needs a length annotation for it because macro_location is a pointer to something that is not a struct, basically. Otherwise, calling gengtype on the resulting gtype.state yields: gcc/fix-master/gcc/../libcpp/include/line-map.h:168: field `(*x).info_ordinary.maps[i0].d.macro.macro_locations' is pointer to unimplemented type This is because with no annotation, the information for "macro_locations" that we have in the generated gtype.state is: (!pair "macro_locations" (!type already_seen 6) (!srcfileloc "../libcpp/include/line-map.h" 168) nil) With the gengtype length annotation, we have: (!pair "macro_locations" (!type already_seen 6) (!srcfileloc "../libcpp/include/line-map.h" 168) (!options (!option length string "2 * %h.n_tokens"))) The important thing to notice there is that in the latest case, there is a "length" option (or attribute) that is present in the description. Then looking at the walk_type function in gengtype.c, we see: case TYPE_POINTER: { ... if (!length) { if (!UNION_OR_STRUCT_P (t->u.p) && t->u.p->kind != TYPE_PARAM_STRUCT) { error_at_line (d->line, "field `%s' is pointer to unimplemented type", d->val); break; } ... The 'length' variable not being set to zero there is a consequence of no gengtype length annotation being present in the line-map.h source code. So my question would be, why is gengtype forcing pointers to e.g, scalars to have a length annotation? If this wasn't the case, I think the expensive empty loops wouldn't be generated in the first place, would they?
