This rewrites ranges::construct_at in terms of std::construct_at so
that we can piggy back on the compiler's existing support for
recognizing placement new within std::construct_at during constexpr
evaluation instead of having to additionally teach the compiler about
ranges::construct_at.
While we're here, we should also make ranges::construct_at conditionally
noexcept like std::construct_at.
Tested on x86_64-pc-linux-gnu, does this look OK for trunk?
libstdc++-v3/ChangeLog:
PR libstdc++/95788
* include/bits/ranges_uninitialized.h:
(__construct_at_fn::operator()): Just call std::construct_at.
Declare it conditionally noexcept.
* testsuite/20_util/specialized_algorithms/construct_at/95788.cc:
New test.
---
.../include/bits/ranges_uninitialized.h | 6 +--
.../construct_at/95788.cc | 40 +++++++++++++++++++
2 files changed, 42 insertions(+), 4 deletions(-)
create mode 100644
libstdc++-v3/testsuite/20_util/specialized_algorithms/construct_at/95788.cc
diff --git a/libstdc++-v3/include/bits/ranges_uninitialized.h
b/libstdc++-v3/include/bits/ranges_uninitialized.h
index d758078fc03..def086508fb 100644
--- a/libstdc++-v3/include/bits/ranges_uninitialized.h
+++ b/libstdc++-v3/include/bits/ranges_uninitialized.h
@@ -496,10 +496,8 @@ namespace ranges
requires requires { ::new (declval<void*>()) _Tp(declval<_Args>()...); }
constexpr _Tp*
operator()(_Tp* __location, _Args&&... __args) const
- {
- return ::new (__detail::__voidify(*__location))
- _Tp(std::forward<_Args>(__args)...);
- }
+ noexcept(noexcept(std::construct_at(__location, declval<_Args>()...)))
+ { return std::construct_at(__location, std::forward<_Args>(__args)...); }
};
inline constexpr __construct_at_fn construct_at{};
diff --git
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/construct_at/95788.cc
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/construct_at/95788.cc
new file mode 100644
index 00000000000..aeb04de1ea3
--- /dev/null
+++
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/construct_at/95788.cc
@@ -0,0 +1,40 @@
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library. This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3. If not see
+// <http://www.gnu.org/licenses/>.
+
+// { dg-options "-std=gnu++2a" }
+// { dg-do compile { target c++2a } }
+
+#include <memory>
+
+constexpr bool test01()
+{
+ const int sz{1};
+ int* data{std::allocator<int>{}.allocate(sz)};
+ static_assert(noexcept(std::ranges::construct_at(data, 42)));
+ std::ranges::construct_at(data, 42);
+ if (*data != 42)
+ return false;
+ std::ranges::destroy_at(data);
+ std::allocator<int>{}.deallocate(data, sz);
+ return true;
+}
+
+static_assert(test01());
+
+struct S { S(); };
+S *p;
+static_assert(!noexcept(std::ranges::construct_at(p)));
--
2.28.0.651.g306ee63a70
