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From: Florian Weimer <fweimer@redhat.com>
To: Jonathan Wakely <jwakely.gcc@gmail.com>
Cc: "Jonathan Wakely via Libstdc++" <libstdc++@gcc.gnu.org>,
	 Jonathan Wakely <jwakely@redhat.com>,
	 gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] libstdc++: Allow std::condition_variable waits to be cancelled [PR103382]
Date: Tue, 07 Dec 2021 22:52:08 +0100	[thread overview]
Message-ID: <87tufkm6bb.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <CAH6eHdSfwrjUf3VfZb-QN9i8TCpFtXqAHcfkPJiwvjknCe0S+Q@mail.gmail.com> (Jonathan Wakely's message of "Tue, 7 Dec 2021 21:38:26 +0000")

* Jonathan Wakely:

> On Tue, 7 Dec 2021, 21:20 Florian Weimer via Libstdc++, <libstdc++@gcc.gnu.org>
> wrote:
>
>  * Jonathan Wakely via Libstdc:
>
>  > If necessary we could keep the terminate-on-cancellation behaviour as
>  > _ZNSt18condition_variable4waitERSt11unique_lockISt5mutexE@GLIBCXX_3.4.11
>  > and export the new behaviour as @@GLIBCXX_3.4.30, although this patch
>  > doesn't do that.
>
>  Note that if this fix escapes into the wild and then you have to make
>  the symbol version change, you will break newer applications.  In a few
>  cases in glibc, we proactively added aliases at a different symbol
>  version, but with the same implementation (at first).
>
> To be safe, we probably should preserve the old behaviour for the old
> version of the symbol. If we decide that the new behaviour is always
> preferable, we could change that later by making the old symbol an
> alias for the new. If we don't decide that, we'll be glad we made it a
> separate symbol.

On the other hand, with separate versions, it's possible to reintroduce
the old behavior at a later date, as a bugfix.  It's not strictly
necessary to do that work upfront.  It's just nice to have this option.

> I'll see if I can get it working with two versioned symbols. We don't
> actually do that in libstdc++ currently, we only have a single version
> of every symbol.

Ping me if you want to discuss options. 8->

Out of curiosity—do you support building libstdc++ (the shared object)
with a different compiler than the included GCC?

Thanks,
Florian


  reply	other threads:[~2021-12-07 21:52 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-07 20:58 Jonathan Wakely
2021-12-07 21:18 ` Florian Weimer
2021-12-07 21:38   ` Jonathan Wakely
2021-12-07 21:52     ` Florian Weimer [this message]
2021-12-08  0:36       ` Jonathan Wakely
2021-12-08 17:26         ` Jonathan Wakely
2021-12-08 17:36           ` Ville Voutilainen
2021-12-08 18:14             ` Jonathan Wakely
2021-12-09 23:30           ` Jonathan Wakely

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