On Thu, 28 Jun 2018, Richard Biener wrote:
>
> The fortran FE creates array descriptor types via build_distinct_type_copy
> which ends up re-using the TYPE_FIELDs chain of FIELD_DECLs between
> types in different type-variant chains. While that seems harmless
> in practice it breaks once we try to generate C-like debug info for
> it because dwarf2out doesn't expect such sharing to occur (and I
> wouldn't be surprised of other odd behavior elsewhere that simply
> doesn't manifest in a as fatal way as PR86321).
>
> We generate C-like debug info when you use LTO and -g0 at compile-time
> and -g at link-time (that's the way targets w/o debug-copy implementation
> end up wired). For non-LTO we avoid directly generating debug for
> the array descriptor types by detecting them via a langhook.
>
> The solution seems to be to adhere to the invariant that TYPE_FIELDs
> (and thus FIELD_DECL) sharing is only valid between variant types
> and their main variant. Thus, copy the chain.
>
> Bootstrap / regtest pending on x86_64-unknown-linux-gnu.
>
> I suppose verify_type () could check proper ownership of the
> FIELD_DECLs (simply verify that DECL_CONTEXT is TYPE_MAIN_VARIANT).
> But I guess this may break in different ways. Honza - did you
> originally try to verify that? It currently says
>
> for (tree fld = TYPE_FIELDS (t); fld; fld = TREE_CHAIN (fld))
> {
> /* TODO: verify properties of decls. */
> if (TREE_CODE (fld) == FIELD_DECL)
> ;
> ...
So at least for class Foo { enum Bar { BAZ }; }; the CONST_DECL for
BAZ appears in the TYPE_FIELDS for Foo and has DECL_CONTEXT Bar ...
Likely dwarf2out also has the following "hack" to deal with this:
gen_decl_die (tree decl, tree origin, struct vlr_context *ctx,
dw_die_ref context_die)
{
...
case CONST_DECL:
if (!is_fortran () && !is_ada ())
{
/* The individual enumerators of an enum type get output when we
output
the Dwarf representation of the relevant enum type itself.
*/
break;
}
Richard.
>
> OK for trunk?
>
> Thanks,
> Richard.
>
> 2018-06-28 Richard Biener <rguent...@suse.de>
>
> fortran/
> PR lto/86321
> * trans-types.c (gfc_get_array_type_bounds): Unshare TYPE_FIELDs
> for the distinct type copy.
>
> Index: gcc/fortran/trans-types.c
> ===================================================================
> --- gcc/fortran/trans-types.c (revision 262132)
> +++ gcc/fortran/trans-types.c (working copy)
> @@ -1923,6 +1923,14 @@ gfc_get_array_type_bounds (tree etype, i
>
> base_type = gfc_get_array_descriptor_base (dimen, codimen, restricted);
> fat_type = build_distinct_type_copy (base_type);
> + /* Unshare TYPE_FIELDs. */
> + for (tree *tp = &TYPE_FIELDS (fat_type); *tp; tp = &DECL_CHAIN (*tp))
> + {
> + tree next = DECL_CHAIN (*tp);
> + *tp = copy_node (*tp);
> + DECL_CONTEXT (*tp) = fat_type;
> + DECL_CHAIN (*tp) = next;
> + }
> /* Make sure that nontarget and target array type have the same canonical
> type (and same stub decl for debug info). */
> base_type = gfc_get_array_descriptor_base (dimen, codimen, false);
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
