From: Rainer Orth <ro@CeBiTec.Uni-Bielefeld.DE>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: Jonathan Wakely via Gcc-patches <gcc-patches@gcc.gnu.org>,
"libstdc++" <libstdc++@gcc.gnu.org>
Subject: Re: [committed] libstdc++: Fix undefined shift when _Atomic_word is 64-bit
Date: Thu, 09 Dec 2021 13:28:50 +0100 [thread overview]
Message-ID: <yddzgpaq7wd.fsf@CeBiTec.Uni-Bielefeld.DE> (raw)
In-Reply-To: <CACb0b4kFPDWmG-u-QMznjWwbCn53etpq16X2F0=Lr3ftQzX-6w@mail.gmail.com> (Jonathan Wakely's message of "Wed, 8 Dec 2021 23:47:13 +0000")
Hi Jonathan,
>> > Ah yes, so we need to disable this optimization. Patch coming up ...
>>
>> Gah, I remembered to check that:
>>
>> constexpr bool __double_word
>> = sizeof(long long) == 2 * sizeof(_Atomic_word);
>> // The ref-count members follow the vptr, so are aligned to
>> // alignof(void*).
>> constexpr bool __aligned = __alignof(long long) <= alignof(void*);
>> if _GLIBCXX17_CONSTEXPR (__lock_free && __double_word && __aligned)
>>
>>
>> But for C++11 and C++14 that is a normal runtime condition not
>> if-constexpr, so the undefined shift still gets compiled, even though
>> it can never be reached at runtime.
>
> Fixed like so. Tested sparc-sun-solaris2.11, pushed to trunk.
great, thanks a lot.
Rainer
--
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University
prev parent reply other threads:[~2021-12-09 12:28 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-17 20:49 [PATCH] libstdc++: Skip atomic instructions in _Sp_counted_base::_M_release when both counts are 1 Maged Michael
2021-01-05 16:19 ` Maged Michael
2021-06-10 14:41 ` Maged Michael
2021-07-16 13:54 ` Jonathan Wakely
2021-07-16 15:55 ` Maged Michael
2021-08-02 13:23 ` Maged Michael
2021-08-02 13:29 ` Maged Michael
2021-08-03 20:59 ` Jonathan Wakely
2021-08-04 15:32 ` Jonathan Wakely
2021-08-04 15:47 ` Maged Michael
2021-08-04 15:52 ` Jonathan Wakely
2021-08-04 17:19 ` Maged Michael
2021-08-04 17:34 ` Maged Michael
2021-08-04 19:32 ` Jonathan Wakely
2021-08-04 19:48 ` Maged Michael
2021-12-08 11:49 ` Jonathan Wakely
2021-12-08 19:15 ` Rainer Orth
2021-12-08 19:21 ` Jonathan Wakely
2021-12-08 19:27 ` Jonathan Wakely
2021-12-08 23:47 ` [committed] libstdc++: Fix undefined shift when _Atomic_word is 64-bit Jonathan Wakely
2021-12-09 12:28 ` Rainer Orth [this message]
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