From: Marc Glisse <marc.glisse@inria.fr>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: libstdc++ <libstdc++@gcc.gnu.org>,
Matthias Kretz <m.kretz@gsi.de>,
gcc Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] libstdc++: Implement std::unreachable() for C++23 (P0627R6)
Date: Thu, 31 Mar 2022 20:21:32 +0200 (CEST) [thread overview]
Message-ID: <147e97d-41ab-98d-7721-a6cf2e0ddeb@hippo.saclay.inria.fr> (raw)
In-Reply-To: <CACb0b4k-t6LQo_nGC=+QQwybTnr444m30mioP28Ag8BoLaHQ6A@mail.gmail.com>
On Thu, 31 Mar 2022, Jonathan Wakely wrote:
> On Thu, 31 Mar 2022 at 17:03, Marc Glisse via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
>>
>> On Thu, 31 Mar 2022, Matthias Kretz via Gcc-patches wrote:
>>
>>> I like it. But I'd like it even more if we could have
>>>
>>> #elif defined _UBSAN
>>> __ubsan_invoke_ub("reached std::unreachable()");
>>>
>>> But to my knowledge UBSAN has no hooks for the library like this (yet).
>>
>> -fsanitize=undefined already replaces __builtin_unreachable with its own
>> thing, so I was indeed going to ask if the assertion / trap provide a
>> better debugging experience compared to plain __builtin_unreachable, with
>> the possibility to get a stack trace (UBSAN_OPTIONS=print_stacktrace=1),
>> etc? Detecting if (the right subset of) ubsan is enabled sounds like a
>> good idea.
>
> Does UBsan define a macro that we can use to detect it?
https://github.com/google/sanitizers/issues/765 seems to say no (it could
be outdated though), but they were asking for use cases to motivate adding
one. Apparently there is a macro for clang, although I don't think it is
fine-grained.
Adding one to cppbuiltin.cc testing SANITIZE_UNREACHABLE looks easy, maybe
we can do just this one, we don't need to go overboard and define macros
for all possible suboptions of ubsan right now.
I don't think any of that prevents from pushing your patch as is for
gcc-12.
--
Marc Glisse
next prev parent reply other threads:[~2022-03-31 18:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-31 15:30 Jonathan Wakely
2022-03-31 15:50 ` Matthias Kretz
2022-03-31 15:59 ` Xi Ruoyao
2022-03-31 16:01 ` Marc Glisse
2022-03-31 16:05 ` Jonathan Wakely
2022-03-31 18:21 ` Marc Glisse [this message]
2022-04-01 11:33 ` Jonathan Wakely
2022-04-01 11:56 ` Matthias Kretz
2022-04-01 13:01 ` Jonathan Wakely
2022-03-31 16:02 ` Jonathan Wakely
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