Re: [RFC/RFA] Add support for the --readnever command-line option (DWARF only)

Pedro Alves
2016-10-04T18:07:04Z

On 07/12/2016 03:27 PM, Yao Qi wrote:
> Hi Joel,
>
> On Wed, Jul 6, 2016 at 9:54 PM, Joel Brobecker <brobecker@adacore.com> wrote:
>> Hello,
>>
>> One of our customers asked us about this option, which they could
>> see as being available in the version of GDB shipped by RedHat but
>> not in the version that AdaCore supports.
>>
>> The purpose of this option is to turn the load of debugging information
>> off. The implementation proposed here is mostly a copy of the patch
>> distributed with RedHat Fedora, and looking at the patch itself and
>> the history, I can see some reasons why it was never submitted:
>
> Andrew Cagney posted the patch
> https://www.sourceware.org/ml/gdb/2004-11/msg00216.html
>
>> - The patch appears to have been introduced as a workaround, at
>> least initially;
>> - The patch is far from perfect, as it simply shunts the load of
>> DWARF debugging information, without really worrying about the
>> other debug format.
>> - Who really does non-symbolic debugging anyways?
>
> The reason, IMO, it was posted is that people want GDB avoid reading
> debug info and efficiently dump stack backtrace. I think Red Hat people
> must know why Fedora is shipping this patch.
>
> I don't object to this approach.
>

This predates my gdb involvement, I don't really know the history.
Maybe Jan knows.

In any case, I don't object to the approach.

Is this skipping _unwind_ info as well though? I think the
documentation should be clear on that, because if it does
skip dwarf info for unwinding as well, then you
may get a faster, but incorrect backtrace.

Thanks,
Pedro Alves