https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101431
--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #4)
> > cat tmp/t.c
> void foo(int i) {}
> > gcc-11 -g -o tmp/t.o tmp/t.c -c
>
> and the DWARF ends up
>
> <0><c>: Abbrev Number: 1 (DW_TAG_compile_unit)
> <d> DW_AT_producer : (indirect string, offset: 0x0): GNU C17 11.1.1
> 20210428 -mtune=generic -march=x86-64 -g
> <11> DW_AT_language : 29 (C11)
> <12> DW_AT_name : (indirect line string, offset: 0x0): tmp/t.c
> <16> DW_AT_comp_dir : (indirect line string, offset: 0x8): /
> <1a> DW_AT_low_pc : 0x0
> <22> DW_AT_high_pc : 0xa
> <2a> DW_AT_stmt_list : 0x0
>
> ...
> The Directory Table (offset 0x22, lines 2, columns 1):
> Entry Name
> 0 (indirect line string, offset: 0xa): tmp
> 1 (indirect line string, offset: 0xe): tmp
>
> The File Name Table (offset 0x30, lines 2, columns 2):
> Entry Dir Name
> 0 0 (indirect line string, offset: 0x12): tmp/t.c
> 1 1 (indirect line string, offset: 0x1a): t.c
>
> I suspect this is because of how GCC and gas together end up producing
> .debug_line - we have
>
> .file "t.c"
> .text
> ...
> foo:
> .LFB0:
> .file 1 "tmp/t.c"
> ...
> .section .debug_line,"",@progbits
> .Ldebug_line0:
> .file 0 "/" "tmp/t.c"
>
> but this .file 0 ends up taking the place of comp-dir and it also
> ends up duplicating the file entry for t.c unnecessarily. I'm not
> familiar with how the DWARF5 stuff was set up so I hope somebody
> else can have a look.
>
> Note the referenced testcase in github uses -gsplit-dwarf.
This was with binutils 2.36.1 and GCC configured against that.
