[PATCH] Fix gnu-versioned-namespace build

[François Dumont]

On 30/10/20 2:37 pm, Jonathan Wakely wrote:
> On 30/10/20 13:23 +0000, Jonathan Wakely wrote:
>> On 30/10/20 13:59 +0100, François Dumont via Libstdc++ wrote:
>>> The gnu-versioned-namespace build is broken.
>>>
>>> The fix in charconv/floating_from_chars.cc is quite trivial. I am 
>>> not so sure about the fix in sstream-inst.cc.
>>
>> The change for src/c++20/sstream-inst.cc is OK to commit. It would
>> probably be better to not build that file at all if the cxx11 ABI is
>> not supported at all, but then the src/c++20 directory would be empty
>> and I'm not sure if that would work. So just making the file empty is
>> fine.
>>
>> The change for from_chars is not OK. With your change the <charconv>
>> header doesn't declare those functions if included by a file using the
>> old ABI. That's wrong, they should be declared unconditionally.
>>
>> I see two ways to fix it. Either make the declarations in the header
>> depend on ! _GLIBCXX_INLINE_VERSION (so they're disabled for
>> gnu-versioned namespace) or fix the code in floating_from_chars to not
>> use a pmr::memory_resource for allocation in the versioned namespace
>> build.
>
> Here's a patch for the second way.
>
> A third way to fix it would be to make basic_string work with C++
> allocators, so that pmr::string is usable for the gnu-versioned
> namespace.
>
> And the fourth would be to switch the versioned namespace to use the
> new ABI unconditionally, instead of using the old ABI unconditionally.
>
>
Can I commit this one once tested then ?

I'll try to put the fourth way in place however.

Thanks,

François