From 27c792895bd809115c1f70672835b7fdff74d318 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Wed, 20 Jan 2021 18:51:04 +0100 Subject: [PATCH] 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 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 | 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::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 (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); + } } } -- 2.30.2