Another version with the major enhancement that COW string is not 
explicitly instantiated anymore. That's ~100ko saved in resulting lib, 
not too bad.

Note that this patch is also smaller cause I removed the regenerated 
parts from it. We got time but can you confirmed that when approved I'll 
also have to commit the regenerated files ?

François


On 17/08/2023 19:22, Jonathan Wakely wrote:
> On Sun, 13 Aug 2023 at 14:27, François Dumont via Libstdc++
> <libstdc++@gcc.gnu.org> wrote:
>> Here is the fixed patch tested in all 3 modes:
>>
>> - _GLIBCXX_USE_DUAL_ABI
>>
>> - !_GLIBCXX_USE_DUAL_ABI && !_GLIBCXX_USE_CXX11_ABI
>>
>> - !_GLIBCXX_USE_DUAL_ABI && _GLIBCXX_USE_CXX11_ABI
>>
>> I don't know what you have in mind for the change below but I wanted to
>> let you know that I tried to put COW std::basic_string into a nested
>> __cow namespace when _GLIBCXX_USE_CXX11_ABI. But it had more impact on
>> string-inst.cc so I preferred the macro substitution approach.
> I was thinking of implementing the necessary special members functions
> of __cow_string directly, so they are ABI compatible with the COW
> std::basic_string but don't actually reuse the code. That would mean
> we don't need to compile and instantiate the whole COW string just to
> use a few members from it. But that can be done later, the macro
> approach seems OK for now.
>
>> There are some test failing when !_GLIBCXX_USE_CXX11_ABI that are
>> unrelated with my changes. I'll propose fixes in coming days.
> Which tests? I run the entire testsuite with
> -D_GLIBCXX_USE_CXX11_ABI=0 several times per day and I'm not seeing
> failures.
>
> I'll review the patch ASAP, thanks for working on it.
>