Re: working with split debug files and sectionless ELFs

Aleksandar Ristovski
2011-10-14T17:31:06Z

On 11-10-14 01:07 PM, Mike Frysinger wrote:
> On Friday 14 October 2011 11:49:24 Jan Kratochvil wrote:
>> On Fri, 14 Oct 2011 17:38:30 +0200, Aleksandar Ristovski wrote:
>>> On 11-10-14 11:27 AM, Mike Frysinger wrote:
>>>> check out symfile.c:find_separate_debug_file_by_debuglink(). i hacked
>>>> it locally so that when get_debug_link_info() returns NULL, the code
>>>> would fall back to searching for the basename(argv[0]) + ".debug" of
>>>> the ELF in question. that seemed to do what i want: "just work".
>>>
>>> Ok, so the problem is that if debuglink is missing, gdb just gives up.
>>>
>>> FWIW, what you are proposing makes sense to me. Maybe make it an
>>> optional behaviour?
>>
>> The problem is the ".debug" extension is stored in .debug_link and it is
>> not assumed by GDB so far. And for example Debian does not use it at all.
>
> that's why it was a hack. i think it reasonable that if there is no debug
> info to first look for the file name itself, and then look for the file name with
> a .debug suffix.
>
> so `gdb prog` where prog is found at /usr/bin/prog would default to
> /usr/lib/debug/usr/bin/prog followed by /usr/lib/debug/usr/bin/prog.debug (and
> obviously /usr/lib/debug/ is the existing configurable setup and not a
> hardcoded path).
>
> i'm thinking of the fallback/default behavior here. none of this would
> preclude the existing explicit options that gdb has available.
> -mike

I would prefer to not have gdb assume any suffix. When I said your
proposal made sense, I did not go into the implementation details. I
agree this would be useful in principle - but would strongly suggest not
to hard-code such a suffix, fallback or not.

If suffix is desired, than at a minimum make it optional. Something like
(gdb) set debug-file-suffix .debug
You can make default settable at configure time.

If separate info is in a separate directory, suffix quite possibly is
not needed at all; it does make a lot of sense if symbol file is in the
same directory as the binary itself.

Further, it might not be .debug at all (e.g. we prefer using .sym).

---
Aleksandar