From: Matthias Kretz <m.kretz@gsi.de>
To: <gcc-patches@gcc.gnu.org>, <libstdc++@gcc.gnu.org>
Subject: Re: [PATCH] libstdc++: Implement std::unreachable() for C++23 (P0627R6)
Date: Thu, 31 Mar 2022 17:50:33 +0200 [thread overview]
Message-ID: <3572914.e9J7NaK4W3@minbar> (raw)
In-Reply-To: <20220331153029.1898244-1-jwakely@redhat.com>
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).
and...
On Thursday, 31 March 2022 17:30:29 CEST Jonathan Wakely via Gcc-patches
wrote:
> diff --git a/libstdc++-v3/include/std/utility
> b/libstdc++-v3/include/std/utility index 0d7f8954c5a..e5b5212381d 100644
> --- a/libstdc++-v3/include/std/utility
> +++ b/libstdc++-v3/include/std/utility
> @@ -186,6 +186,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> constexpr underlying_type_t<_Tp>
> to_underlying(_Tp __value) noexcept
> { return static_cast<underlying_type_t<_Tp>>(__value); }
> +
> +#define __cpp_lib_unreachable 202202L
> + [[noreturn,__gnu__::__always_inline__]]
> + void
> + unreachable()
> + {
> +#ifdef _GLIBCXX_DEBUG
> + std::__glibcxx_assert_fail("<utility>", 0, "std::unreachable()",
> + "inconceivable!");
Funny message, but it should be more helpful, IMHO. :)
-Matthias
> +#elif defined _GLIBCXX_ASSERTIONS
> + __builtin_trap();
> +#else
> + __builtin_unreachable();
> +#endif
> + }
--
──────────────────────────────────────────────────────────────────────────
Dr. Matthias Kretz https://mattkretz.github.io
GSI Helmholtz Centre for Heavy Ion Research https://gsi.de
stdₓ::simd
──────────────────────────────────────────────────────────────────────────
next prev parent reply other threads:[~2022-03-31 15:50 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 [this message]
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
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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