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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/108619] Compilation error if the construct method of
 the allocator isn't implemented and the detructor of value_type is private
Date: Tue, 31 Jan 2023 21:59:08 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108619

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2023-01-31

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #5)
> I missed -std=3Dc++20 part before. The rebind fixes the compiliation issue
> without -std=3Dc++20 ....

Right, but the bug report is about c++20 mode, and the rebind isn't needed =
in
C++20 (because std::allocator<T>::rebind doesn't exist, so the default
implementation of rebinding does the right thing for alloc<T>).

(In reply to Andrew Pinski from comment #6)
> With clang and libc++ we get:
>=20
> /opt/compiler-explorer/clang-trunk-20230131/bin/../include/c++/v1/__memor=
y/
> uninitialized_algorithms.h:597:3: error: static assertion failed due to
> requirement '__is_cpp17_move_insertable<b::alloc<a>, void>::value': The
> specified type does not meet the requirements of Cpp17MoveInsertable
>   static_assert(__is_cpp17_move_insertable<_Alloc>::value,
>   ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>=20
> Which I think is the best error message really. libstdc++v3 should add a
> similar static assert I think.

I think this is a libc++ bug in their __cpp17_move_insertable trait, which =
just
uses is_move_constructible here, which is false because of the private
destructor.

I agree there's a bug here, but I'm not sure where yet.=