From: Jonathan Wakely <jwakely.gcc@gmail.com>
To: "François Dumont" <frs.dumont@gmail.com>
Cc: Jonathan Wakely <jwakely@redhat.com>,
"libstdc++" <libstdc++@gcc.gnu.org>,
waffl3x <waffl3x@protonmail.com>,
gcc-patches <gcc-patches@gcc.gnu.org>
Subject: Re: [PATCH] minor optimization bug in basic_string move assignment
Date: Sat, 4 Feb 2023 13:30:58 +0000 [thread overview]
Message-ID: <CAH6eHdS46wBC4rQM14K8uqQr4RgDc--FMnHKXs-sVUHb_T6P3A@mail.gmail.com> (raw)
In-Reply-To: <9f3648a8-0cbd-4fe8-1a9d-1902d9ab415c@gmail.com>
[-- Attachment #1: Type: text/plain, Size: 2721 bytes --]
On Sat, 4 Feb 2023, 13:12 François Dumont via Libstdc++, <
libstdc++@gcc.gnu.org> wrote:
> On 03/02/23 15:50, Jonathan Wakely wrote:
> > On Wed, 25 Jan 2023 at 18:38, François Dumont <frs.dumont@gmail.com>
> wrote:
> >> Let's submit a proper patch proposal then.
> >>
> >> The occasion for me to ask if there is any reason for cow string not
> >> being C++11 allocator compliant ? Just lack of interest ?
> > Mostly lack of interest, but also I don't really want to "encourage"
> > the use of the old string by investing lots of maintenance effort into
> > it. If you want new features like C++11 Allocators and
> > resize_and_overwrite etc then you should use the new type.
> >
> > I don't remember if there were any actual blockers that made it
> > difficult to support stateful allocators in the COW string. I might
> > have written something about it in mails to the list when I was adding
> > the SSO string, but I don't remember now.
>
> Ok, thanks for feedback. I won't bother then.
>
> >
> > Anyway, for this patch ...
> >
> >> I wanted to consider it to get rid of the __gnu_debug::_Safe_container
> >> _IsCxx11AllocatorAware template parameter.
> >>
> >> libstdc++: Optimize basic_string move assignment
> >>
> >> Since resolution of Issue 2593 [1] we can consider that equal
> >> allocators
> >> before the propagate-on-move-assignment operations will still be
> equal
> >> afterward.
> >>
> >> So we can extend the optimization of transfering the storage of
> the
> >> move-to
> >> instance to the move-from one that is currently limited to always
> equal
> >> allocators.
> >>
> >> [1] https://cplusplus.github.io/LWG/issue2593
> >>
> >> libstdc++-v3/ChangeLog:
> >>
> >> * include/bits/basic_string.h (operator=(basic_string&&)):
> >> Transfer move-to
> >> storage to the move-from instance when allocators are
> equal.
> >> *
> >> testsuite/21_strings/basic_string/allocator/char/move_assign.cc
> (test04):
> >> New test case.
> >>
> >> Tested under linux x86_64, ok to commit ?
> > OK for trunk, thanks!
> >
> > +Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
>
> Should I have added this to the commit ?
>
> If so sorry, I haven't.
>
No problem!
I think it would be a good habit for us to all start doing that (copying
the glibc project), to thank people who take the time to do a review. I
don't really mind if my name gets recorded as reviewer, but I'm going to
try to remember to add Reviewed-by: when I review something. And that might
encourage others to do the same, and to do more reviewing :-)
>
prev parent reply other threads:[~2023-02-04 13:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-03 23:11 waffl3x
2023-01-04 18:20 ` François Dumont
2023-01-17 19:18 ` Jonathan Wakely
2023-01-25 18:38 ` [PATCH] " François Dumont
2023-02-03 14:50 ` Jonathan Wakely
2023-02-04 13:11 ` François Dumont
2023-02-04 13:30 ` Jonathan Wakely [this message]
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