Re: [PATCH] minor optimization bug in basic_string move assignment

["François Dumont" <frs.dumont@gmail.com>]

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.