[PATCH] Fix gnu-versioned-namespace build

[Jonathan Wakely]

On 30/10/20 13:38 +0000, 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++

Oops, I meant "make the old basic_string work with C++11 allocators"
of course.


>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.