https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85339
Bug ID: 85339
Summary: [8 Regression] With early LTO debug the early DWARF
misses line-info
Product: gcc
Version: 8.0.1
Status: UNCONFIRMED
Keywords: lto, wrong-debug
Severity: normal
Priority: P3
Component: lto
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
CC: jakub at gcc dot gnu.org, marxin at gcc dot gnu.org
Target Milestone: ---
dwz rightfully complains about bogus DW_AT_decl_file (and also _line/_column?)
beause the early debug doesn't contain .debug_line. split-dwarf adds a
DW_AT_stmt_list pointing to the main files line tables but obviously
the early debug dwarf needs to stand on its own.
I'm not sure how to access line-info from gdb say for
<1><19>: Abbrev Number: 2 (DW_TAG_structure_type)
<1a> DW_AT_name : X
<1c> DW_AT_byte_size : 8
<1d> DW_AT_decl_file : 1
<1e> DW_AT_decl_line : 1
<1f> DW_AT_decl_column : 8
<20> DW_AT_sibling : <0x3b>
<2><24>: Abbrev Number: 3 (DW_TAG_member)
<25> DW_AT_name : a
<27> DW_AT_decl_file : 1
<28> DW_AT_decl_line : 1
<29> DW_AT_decl_column : 16
<2a> DW_AT_type : <0x3b>
<2e> DW_AT_data_member_location: 0
maybe gdb just ignores that info (why do we output it then?). Breakpoints
seem to work just fine beause the LTRANS unit will have a proper .debug_line.
So I'm really not sure what consumer uses the symbolic location attributes
on decls and types?
Note we already output .debug_line into the early debug at -g3 so the fix
might be as simple as enabling that also for -g.
Thus testing the following:
Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c (revision 259308)
+++ gcc/dwarf2out.c (working copy)
@@ -31681,6 +31682,7 @@ static void
dwarf2out_early_finish (const char *filename)
{
set_early_dwarf s;
+ char dl_section_ref[MAX_ARTIFICIAL_LABEL_BYTES];
/* PCH might result in DW_AT_producer string being restored from the
header compilation, so always fill it with empty string initially
@@ -31829,6 +31835,16 @@ dwarf2out_early_finish (const char *file
ctnode != NULL; ctnode = ctnode->next)
add_sibling_attributes (ctnode->root_die);
+ /* AIX Assembler inserts the length, so adjust the reference to match the
+ offset expected by debuggers. */
+ strcpy (dl_section_ref, debug_skeleton_line_section_label);
+ if (XCOFF_DEBUGGING_INFO)
+ strcat (dl_section_ref, DWARF_INITIAL_LENGTH_SIZE_STR);
+
+ if (debug_info_level >= DINFO_LEVEL_TERSE)
+ add_AT_lineptr (comp_unit_die (), DW_AT_stmt_list,
+ dl_section_ref);
+
if (have_macinfo)
add_AT_macptr (comp_unit_die (), DEBUG_MACRO_ATTRIBUTE,
macinfo_section_label);
@@ -31898,11 +31914,6 @@ dwarf2out_early_finish (const char *file
output_macinfo (debug_skeleton_line_section_label, true);
dw2_asm_output_data (1, 0, "End compilation unit");
- /* Emit a skeleton debug_line section. */
- switch_to_section (debug_skeleton_line_section);
- ASM_OUTPUT_LABEL (asm_out_file, debug_skeleton_line_section_label);
- output_line_info (true);
-
if (flag_fat_lto_objects)
{
vec_free (macinfo_table);
@@ -31910,6 +31921,10 @@ dwarf2out_early_finish (const char *file
}
}
+ /* Emit a skeleton debug_line section. */
+ switch_to_section (debug_skeleton_line_section);
+ ASM_OUTPUT_LABEL (asm_out_file, debug_skeleton_line_section_label);
+ output_line_info (true);
/* If we emitted any indirect strings, output the string table too. */
if (debug_str_hash || skeleton_debug_str_hash)
