From: Jonathan Wakely <jwakely@redhat.com>
To: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org
Subject: Re: [committed] libstdc++: Fix std::get<T> for std::tuple [PR101427]
Date: Thu, 15 Jul 2021 16:26:51 +0100 [thread overview]
Message-ID: <YPBTu/BMDpJBgm8l@redhat.com> (raw)
In-Reply-To: <YPBTj47Pvh3Lx3QT@redhat.com>
On 15/07/21 16:26 +0100, Jonathan Wakely wrote:
>The std::get<T> functions relied on deduction failing if more than one
>base class existed for the type T. However the implementation of Core
>DR 2303 (in r11-4693) made deduction succeed (and select the
>more-derived base class).
>
>This rewrites the implementation of std::get<T> to explicitly check for
>more than one occurrence of T in the tuple elements, making it
>ill-formed again. Additionally, the large wall of overload resolution
>errors described in PR c++/101460 is avoided by making std::get<T> use
>__get_helper<I> directly instead of calling std::get<I>, and by adding a
>deleted overload of __get_helper<N> for out-of-range N.
>
>Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
>
>libstdc++-v3/ChangeLog:
>
> PR libstdc++/101427
> * include/std/tuple (tuple_element): Improve static_assert text.
> (__get_helper): Add deleted overload.
> (get<i>(tuple<T...>&&), get<i>(const tuple<T...>&&)): Use
> __get_helper directly.
> (__get_helper2): Remove.
> (__find_uniq_type_in_pack): New constexpr helper function.
> (get<T>): Use __find_uniq_type_in_pack and __get_helper instead
> of __get_helper2.
> * testsuite/20_util/tuple/element_access/get_neg.cc: Adjust
> expected errors.
> * testsuite/20_util/tuple/element_access/101427.cc: New test.
>
>Tested powerpc64le-linux. Committed to trunk.
This should be backported to gcc-11 in time for 11.2 as well. If you
see any problems with it please let me know ASAP.
next prev parent reply other threads:[~2021-07-15 15:26 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-15 15:26 Jonathan Wakely
2021-07-15 15:26 ` Jonathan Wakely [this message]
2021-07-16 22:08 ` [committed] libstdc++: Improve diagnostics for std::get with invalid tuple index Jonathan Wakely
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