On Wed, 20 Jan 2021, Jakub Jelinek wrote:
> Hi!
>
> As mentioned in the PR, with -gdwarf-5 (or -g now) -flto -ffat-lto-objects,
> users can't strip the LTO sections with
> strip -p -R .gnu.lto_* -R .gnu.debuglto_* -N __gnu_lto_v1
> anymore when GCC is configured against recent binutils.
>
> The problem is that in that case .gnu.debuglto_.debug_line_str section is
> then used, which is fine for references to strings in .gnu.debuglto_.*
> sections, but not when those references are in .debug_info section too;
> those should really reference separate strings in .debug_line_str section.
>
> For .gnu.debuglto_.debug_str vs. .debug_str we handle it right, we
> reset_indirect_string the strings and thus force creation of new labels for
> the second time.
> But for DW_FORM_line_strp as the patch shows, there were multiple problems.
> First one was that reset_indirect_string, even when called through traverse
> on debug_line_str_hash, didn't do anything at all (fixed by first hunk).
> The second bug was that the DW_FORM_line_strp strings, which were supposed
> to be only visible through debug_line_str_hash, leaked into debug_str_hash
> (second hunk).
> And the third thing is that when we reset debug_line_str_hash, we should
> still make those strings DW_FORM_line_strp if they are accessed.
> One could do it by reinstantiating DW_FORM_line_strp right away in
> reset_indirect_string and not clear debug_line_str_hash, but that has the
> disadvantage that we then force emitting .debug_line_str strings that aren't
> really needed - we need those from the CU DIEs' DW_AT_name and
> DW_AT_comp_dir attributes, but when emitting .debug_line section through
> assembler, we don't need to emit the strings we only needed for
> .gnu.debuglto_.debug_line which is always emitted by the compiler.
>
> Ok for trunk if this passes bootstrap/regtest?
OK.
Thanks,
Richard.
> 2021-01-20 Jakub Jelinek <ja...@redhat.com>
>
> PR debug/98765
> * dwarf2out.c (reset_indirect_string): Also reset indirect strings
> with DW_FORM_line_strp form.
> (prune_unused_types_update_strings): Don't add into debug_str_hash
> indirect strings with DW_FORM_line_strp form.
> (adjust_name_comp_dir): New function.
> (dwarf2out_finish): Call it on CU DIEs after resetting
> debug_line_str_hash.
>
> --- gcc/dwarf2out.c.jj 2021-01-20 08:32:09.612958930 +0100
> +++ gcc/dwarf2out.c 2021-01-20 15:41:30.343417095 +0100
> @@ -4733,7 +4733,9 @@ int
> reset_indirect_string (indirect_string_node **h, void *)
> {
> struct indirect_string_node *node = *h;
> - if (node->form == DW_FORM_strp || node->form == dwarf_FORM (DW_FORM_strx))
> + if (node->form == DW_FORM_strp
> + || node->form == DW_FORM_line_strp
> + || node->form == dwarf_FORM (DW_FORM_strx))
> {
> free (node->label);
> node->label = NULL;
> @@ -29477,8 +29479,9 @@ prune_unused_types_update_strings (dw_di
> s->refcount++;
> /* Avoid unnecessarily putting strings that are used less than
> twice in the hash table. */
> - if (s->refcount
> - == ((DEBUG_STR_SECTION_FLAGS & SECTION_MERGE) ? 1 : 2))
> + if (s->form != DW_FORM_line_strp
> + && (s->refcount
> + == ((DEBUG_STR_SECTION_FLAGS & SECTION_MERGE) ? 1 : 2)))
> {
> indirect_string_node **slot
> = debug_str_hash->find_slot_with_hash (s->str,
> @@ -31325,6 +31328,33 @@ reset_dies (dw_die_ref die)
> FOR_EACH_CHILD (die, c, reset_dies (c));
> }
>
> +/* reset_indirect_string removed the references coming from DW_AT_name
> + and DW_AT_comp_dir attributes on compilation unit DIEs. Readd them as
> + .debug_line_str strings again. */
> +
> +static void
> +adjust_name_comp_dir (dw_die_ref die)
> +{
> + for (int i = 0; i < 2; i++)
> + {
> + dwarf_attribute attr_kind = i ? DW_AT_comp_dir : DW_AT_name;
> + dw_attr_node *a = get_AT (die, attr_kind);
> + if (a == NULL || a->dw_attr_val.val_class != dw_val_class_str)
> + continue;
> +
> + if (!debug_line_str_hash)
> + debug_line_str_hash
> + = hash_table<indirect_string_hasher>::create_ggc (10);
> +
> + struct indirect_string_node *node
> + = find_AT_string_in_table (a->dw_attr_val.v.val_str->str,
> + debug_line_str_hash);
> + set_indirect_string (node);
> + node->form = DW_FORM_line_strp;
> + a->dw_attr_val.v.val_str = node;
> + }
> +}
> +
> /* Output stuff that dwarf requires at the end of every file,
> and generate the DWARF-2 debugging info. */
>
> @@ -31398,6 +31428,12 @@ dwarf2out_finish (const char *filename)
> {
> debug_line_str_hash->traverse<void *, reset_indirect_string> (NULL);
> debug_line_str_hash = NULL;
> + if (asm_outputs_debug_line_str ())
> + {
> + adjust_name_comp_dir (comp_unit_die ());
> + for (limbo_die_node *node = cu_die_list; node; node = node->next)
> + adjust_name_comp_dir (node->die);
> + }
> }
> }
>
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Maxfeldstrasse 5, 90409 Nuernberg,
Germany; GF: Felix Imendörffer; HRB 36809 (AG Nuernberg)
