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* [gcc r11-6820] debug: Fix up DWARF 5 -g -flto -ffat-lto-objects [PR98765]
@ 2021-01-20 17:58 Jakub Jelinek
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From: Jakub Jelinek @ 2021-01-20 17:58 UTC (permalink / raw)
To: gcc-cvs
https://gcc.gnu.org/g:27c792895bd809115c1f70672835b7fdff74d318
commit r11-6820-g27c792895bd809115c1f70672835b7fdff74d318
Author: Jakub Jelinek <jakub@redhat.com>
Date: Wed Jan 20 18:51:04 2021 +0100
debug: Fix up DWARF 5 -g -flto -ffat-lto-objects [PR98765]
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.
2021-01-20 Jakub Jelinek <jakub@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.
Diff:
---
gcc/dwarf2out.c | 42 +++++++++++++++++++++++++++++++++++++++---
1 file changed, 39 insertions(+), 3 deletions(-)
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index 93e5d15e20a..77ea4948d5e 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -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_die_ref die)
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);
+ }
}
}
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