[Bug gas/28629] New: [gas, --gdwarf-5] File 0 has wrong dir

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=28629

            Bug ID: 28629
           Summary: [gas, --gdwarf-5] File 0 has wrong dir
           Product: binutils
           Version: 2.38 (HEAD)
            Status: NEW
          Severity: normal
          Priority: P2
         Component: gas
          Assignee: unassigned at sourceware dot org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider the following compilation:
...
$ pwd -P
/home/vries/gdb_versions/devel
$ as --gdwarf-5 --64 -o tui-layout-asm-short-prog.o
/home/vries/gdb_versions/devel/src/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S
...

First, lets look at the debug info:
...
$ readelf -wi tui-layout-asm-short-prog.o 
Contents of the .debug_info section:

  Compilation Unit @ offset 0x0:
   Length:        0x24 (32-bit)
   Version:       5
   Unit Type:     DW_UT_compile (1)
   Abbrev Offset: 0x0
   Pointer Size:  8
 <0><c>: Abbrev Number: 1 (DW_TAG_compile_unit)
    <d>   DW_AT_stmt_list   : 0x0
    <11>   DW_AT_low_pc      : 0x0
    <19>   DW_AT_high_pc     : 5
    <1a>   DW_AT_name        : tui-layout-asm-short-prog.S
    <1e>   DW_AT_comp_dir    : /home/vries/gdb_versions/devel
    <22>   DW_AT_producer    : GNU AS 2.37.50
    <26>   DW_AT_language    : 32769    (MIPS assembler)
...

First we have:
...
A DW_AT_comp_dir attribute whose value is a null-terminated string
containing the current working directory of the compilation command that
produced this compilation unit in whatever form makes sense for the host
system.
...

The DW_AT_comp_dir attribute looks correct, it matches pwd -P.

Then we have:
...
A DW_AT_name attribute whose value is a null-terminated string containing
the full or relative path name (relative to the value of the DW_AT_comp_dir
attribute, see below) of the primary source file from which the compilation
unit was derived.
...

That looks incorrect.  It's a relative path name, so it's relative to
/home/vries/gdb_versions/devel, which makes it
/home/vries/gdb_versions/devel/tui-layout-asm-short-prog.S, which is a
non-existent file.

For comparison, we have with dwarf 4 instead:
...
    <19>   DW_AT_name        :
/home/vries/gdb_versions/devel/src/gdb/testsuite/gdb.tui/tui-layout-asm-short-prog.S
    <1d>   DW_AT_comp_dir    : /home/vries/gdb_versions/devel
...

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