Hi,
On Fri, 2020-09-18 at 17:21 +0200, Mark Wielaard wrote:
> On Tue, 2020-09-15 at 20:40 +0200, Jakub Jelinek wrote:
> > Ok, here it is in patch form.
> > I've briefly tested it, with the older binutils I have around (no --gdwarf-N
> > support), with latest gas (--gdwarf-N that can be passed to as even when
> > compiling C/C++ etc. code and emitting .debug_line) and latest gas with
> > Mark's fix
> > reverted (--gdwarf-N support, but can only pass it to as when assembling
> > user .s/.S files, not when compiling C/C++ etc.).
> > Will bootstrap/regtest (with the older binutils) later tonight.
> >
> > 2020-09-15 Jakub Jelinek <ja...@redhat.com>
> >
> > * configure.ac (HAVE_AS_GDWARF_5_DEBUG_FLAG,
> > HAVE_AS_WORKING_DWARF_4_FLAG): New tests.
> > * gcc.c (ASM_DEBUG_DWARF_OPTION): Define.
> > (ASM_DEBUG_SPEC): Use ASM_DEBUG_DWARF_OPTION instead of
> > "--gdwarf2". Use %{cond:opt1;:opt2} style.
> > (ASM_DEBUG_OPTION_DWARF_OPT): Define.
> > (ASM_DEBUG_OPTION_SPEC): Define.
> > (asm_debug_option): New variable.
> > (asm_options): Add "%(asm_debug_option)".
> > (static_specs): Add asm_debug_option entry.
> > (static_spec_functions): Add dwarf-version-gt.
> > (debug_level_greater_than_spec_func): New function.
> > * config/darwin.h (ASM_DEBUG_OPTION_SPEC): Define.
> > * config/darwin9.h (ASM_DEBUG_OPTION_SPEC): Redefine.
> > * config.in: Regenerated.
> > * configure: Regenerated.
>
> Once this is in we can more generally emit DW_FORM_line_str for
> filepaths in CU DIEs for the name and comp_dir attribute. There
> currently is a bit of a hack to do this in dwarf2out_early_finish, but
> that only works when the assembler doesn't emit a DWARF5 .debug_line,
> but gcc does it itself.
>
> What do you think of the attached patch?
>
> DWARF5 has a new string table specially for file paths. .debug_line
> file and dir tables reference strings in .debug_line_str. If a
> .debug_line_str section is emitted then also place CU DIE file
> names and comp dirs there.
>
> gcc/ChangeLog:
>
> * dwarf2out.c (add_filepath_AT_string): New function.
> (asm_outputs_debug_line_str): Likewise.
> (add_filename_attribute): Likewise.
> (add_comp_dir_attribute): Call add_filepath_AT_string.
> (gen_compile_unit_die): Call add_filename_attribute for name.
> (init_sections_and_labels): Init debug_line_str_section when
> asm_outputs_debug_line_str return true.
> (dwarf2out_early_finish): Remove DW_AT_name and DW_AT_comp_dir
> hack and call add_filename_attribute for the remap_debug_filename.
On top of that, we also need the following, which makes sure the actual
compilation directory is used in a DWARF5 .debug_line directory table
(and not just a relative path).
From 66b25bc0a5df06e211b48a54e3b5d33999c24fb6 Mon Sep 17 00:00:00 2001
From: Mark Wielaard <m...@klomp.org>
Date: Tue, 6 Oct 2020 17:41:19 +0200
Subject: [PATCH] debug: Make sure to output .file 0 when generating DWARF5.
When gas outputs DWARF5 .debug_line[_str] then we have to tell it the
comp_dir and main file name for the zero entry line table. Otherwise
gas has to guess at the CU compilation directory and file.
Before a gcc -gdwarf-5 ../src/hello.c line table looked like:
Directory table:
0 ../src (24)
1 ../src (24)
2 /usr/include (31)
File name table:
0 hello.c (16), 0
1 hello.c (16), 1
2 stdio.h (44), 2
With this patch it looks like:
Directory table:
0 /tmp/obj (0)
1 ../src (24)
2 /usr/include (31)
File name table:
0 ../src/hello.c (9), 0
1 hello.c (16), 1
2 stdio.h (44), 2
gcc/ChangeLog:
* dwarf2out.c (dwarf2out_finish): Emit .file 0 entry when
generating DWARF5 .debug_line table through gas.
---
gcc/dwarf2out.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/gcc/dwarf2out.c b/gcc/dwarf2out.c
index a43082864a75..399937a9f310 100644
--- a/gcc/dwarf2out.c
+++ b/gcc/dwarf2out.c
@@ -31764,6 +31764,27 @@ dwarf2out_finish (const char *filename)
ASM_OUTPUT_LABEL (asm_out_file, debug_line_section_label);
if (! output_asm_line_debug_info ())
output_line_info (false);
+ else if (asm_outputs_debug_line_str ())
+ {
+ /* When gas outputs DWARF5 .debug_line[_str] then we have to
+ tell it the comp_dir and main file name for the zero entry
+ line table. */
+ const char *comp_dir, *filename0;
+
+ comp_dir = comp_dir_string ();
+ if (comp_dir == NULL)
+ comp_dir = "";
+
+ filename0 = get_AT_string (comp_unit_die (), DW_AT_name);
+ if (filename0 == NULL)
+ filename0 = "";
+
+ fprintf (asm_out_file, "\t.file 0 ");
+ output_quoted_string (asm_out_file, remap_debug_filename (comp_dir));
+ fputc (' ', asm_out_file);
+ output_quoted_string (asm_out_file, remap_debug_filename (filename0));
+ fputc ('\n', asm_out_file);
+ }
if (dwarf_split_debug_info && info_section_emitted)
{
--
2.18.4
