[PATCH] Fix _GLIBCXX_DEBUG container allocator aware move constructors

[Jonathan Wakely]

On 26/03/21 21:41 +0100, François Dumont via Libstdc++ wrote:
>I review the allocator aware move constructors of _GLIBCXX_DEBUG containers.
>
>I think the recently added __gnu_debug basic_string one is also 
>missing the rvalue reference, no ?

You mean is_nothrow_constructible<Base, Base&&, const Alloc&> instead
of is_nothrow_constructible<Base,Base, const Alloc&>?

No, it's not missing. They mean the exact same thing: Base is an
rvalue, Base&& is an rvalue, and Base& is an lvalue. Writing Base&&
instead of Base is just extra noise that adds no value.


>    libstdc++: _GLIBCXX_DEBUG Fix allocator aware move constructor

The correct term is "allocator-extended move constructor". And is it
really a "fix"? The standard doesn't require a noexcept-specifier on
those constructors, so what we have now is not incorrect, just
suboptimal.

>    Fix several allocator aware move construtor in _GLIBCXX_DEBUG
>    containers.
>
>    libstdc++-v3/ChangeLog:
>            * include/debug/forward_list
>            (forward_list(forward_list&&, const allocator_type&)): Add 
>noexcept qualification.
>            * include/debug/list (list(list&&, const 
>allocator_type&)): Likewise and add
>            call to safe container allocator aware move constructor.
>            * include/debug/string (basic_string(basic_string&&, const 
>_Allocator&)):
>            Check base type allocator aware more constructor.
>            * include/debug/vector (vector(vector&&, const 
>allocator_type&)):
>            Fix noexcept qualification.
>            * 
>testsuite/23_containers/forward_list/cons/noexcept_move_construct.cc:
>            Add allocator aware move constructor noexceot 
>qualification check.
>            * 
>testsuite/23_containers/list/cons/noexcept_move_construct.cc: 
>Likewise.
>
>Tested under linux x86_64.
>
>Ok to commit ?

OK, thanks.