By trying to reuse the existing std::_Construct function as a wrapper
for std::construct_at I introduced regressions, because changing
std::_Construct to return non-void made it ill-formed for array types.
The solution is to revert _Construct to its former state, and change
allocator_traits::construct to explicitly call construct_at instead.
This decouples all the existing callers of _Construct from the new
construct_at requirements.
PR libstdc++/94831
* include/bits/alloc_traits.h (_S_construct): Restore placement
new-expression for C++11/14/17 and call std::construct_at directly
for C++20.
* include/bits/stl_construct.h (_Construct): Revert to non-constexpr
function returning void.
* testsuite/20_util/specialized_algorithms/
uninitialized_value_construct/94831.cc: New test.
* testsuite/23_containers/vector/cons/94831.cc: New test.
Tested powerpc64le-linux, committed to master.
commit 162c40a4c127cc55d701bb8760e17708d0ca2fe0
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Tue Apr 28 23:26:21 2020 +0100
libstdc++: Fix regression in std::_Construct (PR 94831)
By trying to reuse the existing std::_Construct function as a wrapper
for std::construct_at I introduced regressions, because changing
std::_Construct to return non-void made it ill-formed for array types.
The solution is to revert _Construct to its former state, and change
allocator_traits::construct to explicitly call construct_at instead.
This decouples all the existing callers of _Construct from the new
construct_at requirements.
PR libstdc++/94831
* include/bits/alloc_traits.h (_S_construct): Restore placement
new-expression for C++11/14/17 and call std::construct_at directly
for C++20.
* include/bits/stl_construct.h (_Construct): Revert to non-constexpr
function returning void.
* testsuite/20_util/specialized_algorithms/
uninitialized_value_construct/94831.cc: New test.
* testsuite/23_containers/vector/cons/94831.cc: New test.
diff --git a/libstdc++-v3/include/bits/alloc_traits.h
b/libstdc++-v3/include/bits/alloc_traits.h
index 061d353e3f0..6066f48d24c 100644
--- a/libstdc++-v3/include/bits/alloc_traits.h
+++ b/libstdc++-v3/include/bits/alloc_traits.h
@@ -253,7 +253,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
noexcept(noexcept(::new((void*)__p)
_Tp(std::forward<_Args>(__args)...)))
- { std::_Construct(__p, std::forward<_Args>(__args)...); }
+ {
+#if __cplusplus <= 201703L
+ ::new((void*)__p) _Tp(std::forward<_Args>(__args)...);
+#else
+ std::construct_at(__p, std::forward<_Args>(__args)...);
+#endif
+ }
template<typename _Alloc2, typename _Tp>
static _GLIBCXX14_CONSTEXPR auto
diff --git a/libstdc++-v3/include/bits/stl_construct.h
b/libstdc++-v3/include/bits/stl_construct.h
index 5c9a84d9497..72a7cb4712c 100644
--- a/libstdc++-v3/include/bits/stl_construct.h
+++ b/libstdc++-v3/include/bits/stl_construct.h
@@ -65,9 +65,9 @@
* std::destroy_n, and the C++20 function std::construct_at.
* It also provides std::_Construct, std::_Destroy,and std::_Destroy_n
functions
* which are defined in all standard modes and so can be used in C++98-14 code.
- * The _Construct and _Destroy functions will dispatch to construct_at and
- * destroy_at during constant evaluation, because calls to those functions are
- * intercepted by the compiler to allow use in constant expressions.
+ * The _Destroy functions will dispatch to destroy_at during constant
+ * evaluation, because calls to that function are intercepted by the compiler
+ * to allow use in constant expressions.
*/
namespace std _GLIBCXX_VISIBILITY(default)
@@ -104,23 +104,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
*/
#if __cplusplus >= 201103L
template<typename _Tp, typename... _Args>
- constexpr _Tp*
+ inline void
_Construct(_Tp* __p, _Args&&... __args)
- {
-#if __cplusplus > 201703L
- return std::construct_at(__p, std::forward<_Args>(__args)...);
-#else
- return ::new(static_cast<void*>(__p))
_Tp(std::forward<_Args>(__args)...);
-#endif
- }
+ { ::new(static_cast<void*>(__p)) _Tp(std::forward<_Args>(__args)...); }
#else
template<typename _T1, typename _T2>
- inline _T1*
+ inline void
_Construct(_T1* __p, const _T2& __value)
{
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 402. wrong new expression in [some_]allocator::construct
- return ::new(static_cast<void*>(__p)) _T1(__value);
+ ::new(static_cast<void*>(__p)) _T1(__value);
}
#endif
diff --git
a/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc
new file mode 100644
index 00000000000..27506fae09f
--- /dev/null
+++
b/libstdc++-v3/testsuite/20_util/specialized_algorithms/uninitialized_value_construct/94831.cc
@@ -0,0 +1,29 @@
+// 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++17" }
+// { dg-do compile { target c++17 } }
+
+#include <memory>
+
+void
+test01()
+{
+ // PR libstdc++/94831
+ float i[2];
+ std::uninitialized_value_construct(&i, &i + 1);
+}
diff --git a/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc
b/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc
new file mode 100644
index 00000000000..72dfcaae9af
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/cons/94831.cc
@@ -0,0 +1,29 @@
+// 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-do compile { target c++11 } }
+
+#include <vector>
+
+void
+test01()
+{
+ // PR libstdc++/94831.cc
+ // We allow this in C++11 and later as a GNU extension.
+ // FIXME: make it ill-formed when __STRICT_ANSI__ is defined.
+ std::vector<float[2]> v(1u);
+}
