build-ids, .debug_sup and other IDs (Was: [PATCH] Handle DWARF 5 separate debug sections)

[Mark Wielaard]

Hi Nick,

On Wed, Feb 24, 2021 at 05:00:14PM +0000, Nick Clifton wrote:
> > Context is that dwz 0.15 (still not released yet) can now produce
> > standardized DWARF Supplementary Files using a .debug_sup section
> > when using --dwarf-5 -m multifile. See this bug report:
> > https://sourceware.org/bugzilla/show_bug.cgi?id=27440
> 
> Is there somewhere that I can lay my hands on a file containing a
> .debug_sup section and its corresponding supplimentary file ?  I
> would like to test the binutils to make sure that they can support
> them too.

Currently you need dwz git trunk (hopefully we will do a real release
by Monday?). The following will get you a .sup file for dwz itself:

$ git clone git://sourceware.org/git/dwz.git
$ cd dwz
$ ./configure
$ make
$ cp dwz one
$ cp dwz two
$ dwz --dwarf-5 -m sup one two

If you already process .gnu_debugaltlink then processing the
.debug_sup shouldn't be too hard. Just don't expect there to be a
.note.gnu.build-id. Also note that instead of DW_FORM_GNU_alt_ref and
DW_FORM_GNU_alt_strp the one and two files will contain
DW_FORM_ref_sup and DW_FORM_ref_strp.

The formal description of the .debug_sup section can be found in
section 7.3.6 DWARF Supplementary Object Files
http://dwarfstd.org/doc/DWARF5.pdf

Cheers,

Mark