[PATCH] libstdc++: Add error handler for <stacktrace>

[François Dumont]

On 30/11/22 14:07, Jonathan Wakely wrote:
> On Wed, 30 Nov 2022 at 11:57, Jonathan Wakely <jwakely@redhat.com> wrote:
>>
>>
>> On Wed, 30 Nov 2022 at 11:54, Jonathan Wakely <jwakely@redhat.com> wrote:
>>>
>>>
>>> On Wed, 30 Nov 2022 at 06:04, François Dumont via Libstdc++ <libstdc++@gcc.gnu.org> wrote:
>>>> Good catch, then we also need this patch.
>>>
>>> Is it worth printing an error? If we can't show the backtrace because of an error, we can just print nothing there.
>>>
>>> We also need to pass an error handler to the __glibcxx_backtrace_create_state call in formatter.h.
>>>
>>> Now that I look at this code again, why do we need the _M_backtrace_full member? It's always set to the same thing, why can't we just call that function directly?
>>
>> Oh right, I remember now ... because otherwise the libstdc++.so library needs the definition of __glibcxx_backtrace_full.
> I'm testing the attached patch.
>
>
>>> And I think we should use threaded=1 for the __glibcxx_backtrace_create_state call.

You mean that 2 threads could try to assert at the same time.

I don't know what's the rule on the static _Error_formatter instance in 
_S_at. If we have a strong guaranty that only 1 instance will be created 
then I understand why we need threaded=1. Even if in this case the 2 
threads will report the same stacktrace.