On Tue, 10 Dec 2024 at 09:56, Jonathan Wakely <jwakely....@gmail.com> wrote:
>
> On Mon, 9 Dec 2024 at 13:21, Jonathan Wakely <jwak...@redhat.com> wrote:
> >
> > On 09/12/24 13:22 +0100, Giuseppe D'Angelo wrote:
> > >Hello,
> > >
> > >This aligns __is_bitwise_relocatable with its modern meaning, that is,
> > >checking for trivial move construction and destruction.
> >
> > Looks good, thanks.
> >
> > >Thanks,
> > >--
> > >Giuseppe D'Angelo
> >
> > >From 0666e993066818ab0940c61d8d9539e883848b29 Mon Sep 17 00:00:00 2001
> > >From: Giuseppe D'Angelo <giuseppe.dang...@kdab.com>
> > >Date: Mon, 9 Dec 2024 02:11:19 +0100
> > >Subject: [PATCH 3/6] libstdc++: port bitwise relocatable away from
> > >is_trivial
> > >MIME-Version: 1.0
> > >Content-Type: text/plain; charset=UTF-8
> > >Content-Transfer-Encoding: 8bit
> > >
> > >In preparation for the deprecation of is_trivial (P3247R2).
> > >"bitwise relocation" (or "trivial relocation" à la P1144/P2786)
> > >doesn't need the full-fledged notion of triviality, just checking for a
> > >trivial move constructor and a trivial destructor is sufficient.
> > >
> > >libstdc++-v3/ChangeLog:
> > >
> > > * include/bits/stl_uninitialized.h: Amended the
> > > __is_bitwise_relocatable type trait.
> > >
> > >Signed-off-by: Giuseppe D'Angelo <giuseppe.dang...@kdab.com>
> > >---
> > > libstdc++-v3/include/bits/stl_uninitialized.h | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > >diff --git a/libstdc++-v3/include/bits/stl_uninitialized.h
> > >b/libstdc++-v3/include/bits/stl_uninitialized.h
> > >index 2190261134e..916288352d7 100644
> > >--- a/libstdc++-v3/include/bits/stl_uninitialized.h
> > >+++ b/libstdc++-v3/include/bits/stl_uninitialized.h
> > >@@ -1248,7 +1248,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
> > > // Also known as is_trivially_relocatable.
> > > template<typename _Tp, typename = void>
> > > struct __is_bitwise_relocatable
> > >- : is_trivial<_Tp> { };
> > >+ : __and_<is_trivially_move_constructible<_Tp>,
> > >is_trivially_destructible<_Tp>> { };
>
> We need this to depend on is_trivially_copyable too, so we can use memcpy.
In fact, maybe it should *only* care about is_trivially_copyable. We
already know the type must be move constructible and destructible, or
it wouldn't be usable in std::vector in the first place.
I'm going to revert it to is_trivial with the -Wdeprecated diagnostics
disabled. This isn't an appropriate change for stage 3.
>
> I'm testing a fix now to fix bootstrap.
>
>
> > >
> > > template <typename _InputIterator, typename _ForwardIterator,
> > > typename _Allocator>
> > >--
> > >2.34.1
> > >
> >
> >
> >
