libstdc++: Avoid errors in allocator's noexcept-specifier (PR 89510)

This fixes a regression due to the conditional noexcept-specifier on
std::allocator::construct and std::allocator::destroy, as well as the
corresponding members of new_allocator, malloc_allocator, and
allocator_traits. Those noexcept-specifiers were using expressions which
might be ill-formed, which caused errors outside the immediate context
when checking for the presence of construct and destroy in SFINAE
contexts.

The fix is to use the is_nothrow_constructible and
is_nothrow_destructible type traits instead, because those traits are
safe to use even when the construction/destruction itself is not valid.

The is_nothrow_constructible trait will be false for a type that is not
also nothrow-destructible, even if the new-expression used in the
construct function body is actually noexcept. That's not the correct
answer, but isn't a problem because providing a noexcept-specifier on
these functions is not required by the standard anyway. If the answer is
false when it should be true, that's suboptimal but OK (unlike giving
errors for valid code, or giving a true answer when it should be false).

	PR libstdc++/89510
	* include/bits/alloc_traits.h (allocator_traits::_S_construct)
	(allocator_traits::_S_destroy)
	(allocator_traits<allocator<T>>::construct): Use traits in
	noexcept-specifiers.
	* include/bits/allocator.h (allocator<void>::construct)
	(allocator<void>::destroy): Likewise.
	* include/ext/malloc_allocator.h (malloc_allocator::construct)
	(malloc_allocator::destroy): Likewise.
	* include/ext/new_allocator.h (new_allocator::construct)
	(new_allocator::destroy): Likewise.
	* testsuite/20_util/allocator/89510.cc: New test.
	* testsuite/ext/malloc_allocator/89510.cc: New test.
	* testsuite/ext/new_allocator/89510.cc: New test.

(cherry picked from commit b1983f4582bbe060b7da83578acb9ed653681fc8)

diff --git a/libstdc++-v3/include/bits/alloc_traits.h b/libstdc++-v3/include/bits/alloc_traits.h
index cda768bf391b12c956582d40cd179978c564356d..988b2c47dc3d2d9ae05d92503ae2dae748e24327 100644 (file)
--- a/libstdc++-v3/include/bits/alloc_traits.h
+++ b/libstdc++-v3/include/bits/alloc_traits.h
@@ -248,8 +248,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
        _Require<__and_<__not_<__has_construct<_Tp, _Args...>>,
                               is_constructible<_Tp, _Args...>>>
        _S_construct(_Alloc&, _Tp* __p, _Args&&... __args)
-       noexcept(noexcept(::new((void*)__p)
-                         _Tp(std::forward<_Args>(__args)...)))
+       noexcept(std::is_nothrow_constructible<_Tp, _Args...>::value)
        { ::new((void*)__p) _Tp(std::forward<_Args>(__args)...); }
 
       template<typename _Alloc2, typename _Tp>
@@ -262,7 +261,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Alloc2, typename _Tp>
        static void
        _S_destroy(_Alloc2&, _Tp* __p, ...)
-       noexcept(noexcept(__p->~_Tp()))
+       noexcept(std::is_nothrow_destructible<_Tp>::value)
        { __p->~_Tp(); }
 
       template<typename _Alloc2>
@@ -480,7 +479,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
        static void
        construct(allocator_type& __a, _Up* __p, _Args&&... __args)
-       noexcept(noexcept(__a.construct(__p, std::forward<_Args>(__args)...)))
+       noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
        { __a.construct(__p, std::forward<_Args>(__args)...); }
 
       /**

diff --git a/libstdc++-v3/include/bits/allocator.h b/libstdc++-v3/include/bits/allocator.h
index f0f8fe41e31e11e26b7c89b020ced89621212312..664b2ea41274c6b8602501c3d56f8718a11b6eb8 100644 (file)
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -88,14 +88,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
        void
        construct(_Up* __p, _Args&&... __args)
-       noexcept(noexcept(::new((void *)__p)
-                           _Up(std::forward<_Args>(__args)...)))
+       noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
        { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
        void
        destroy(_Up* __p)
-       noexcept(noexcept(__p->~_Up()))
+       noexcept(std::is_nothrow_destructible<_Up>::value)
        { __p->~_Up(); }
 #endif
     };

diff --git a/libstdc++-v3/include/ext/malloc_allocator.h b/libstdc++-v3/include/ext/malloc_allocator.h
index e225923b20f06f803cc8d125c7fd805d7b564362..c8fce2c861c2b442f743757c1e8c1efeb21dd875 100644 (file)
--- a/libstdc++-v3/include/ext/malloc_allocator.h
+++ b/libstdc++-v3/include/ext/malloc_allocator.h
@@ -151,14 +151,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
         void
         construct(_Up* __p, _Args&&... __args)
-       noexcept(noexcept(::new((void *)__p)
-                         _Up(std::forward<_Args>(__args)...)))
+       noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
        { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
         void 
         destroy(_Up* __p)
-       noexcept(noexcept(__p->~_Up()))
+       noexcept(std::is_nothrow_destructible<_Up>::value)
        { __p->~_Up(); }
 #else
       // _GLIBCXX_RESOLVE_LIB_DEFECTS

diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h
index e24539100f9e9885cf0d590a8801740c9fa521f6..22c95efc2d53ac2a5761f595d91ecc8f247415e7 100644 (file)
--- a/libstdc++-v3/include/ext/new_allocator.h
+++ b/libstdc++-v3/include/ext/new_allocator.h
@@ -142,14 +142,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       template<typename _Up, typename... _Args>
        void
        construct(_Up* __p, _Args&&... __args)
-       noexcept(noexcept(::new((void *)__p)
-                           _Up(std::forward<_Args>(__args)...)))
+       noexcept(std::is_nothrow_constructible<_Up, _Args...>::value)
        { ::new((void *)__p) _Up(std::forward<_Args>(__args)...); }
 
       template<typename _Up>
        void
        destroy(_Up* __p)
-       noexcept(noexcept( __p->~_Up()))
+       noexcept(std::is_nothrow_destructible<_Up>::value)
        { __p->~_Up(); }
 #else
       // _GLIBCXX_RESOLVE_LIB_DEFECTS

diff --git a/libstdc++-v3/testsuite/20_util/allocator/89510.cc b/libstdc++-v3/testsuite/20_util/allocator/89510.cc
new file mode 100644 (file)
index 0000000..a3100a2
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/allocator/89510.cc
@@ -0,0 +1,147 @@
+// 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 <memory>
+
+using AT = std::allocator_traits<std::allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, this should not give an error:
+constexpr bool c = has_construct<std::allocator<NoDefault>, NoDefault>::value;
+constexpr bool cv = has_construct<std::allocator<void>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<std::allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<std::allocator<NoDest>, NoDest>::value;
+constexpr bool d2 = has_traits_destroy<std::allocator<int>, NoDest>::value;
+
+std::allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );

diff --git a/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc b/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc
new file mode 100644 (file)
index 0000000..f2ab25a
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/malloc_allocator/89510.cc
@@ -0,0 +1,149 @@
+// 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 <ext/malloc_allocator.h>
+#include <memory>
+#include <type_traits>
+
+using __gnu_cxx::malloc_allocator;
+using AT = std::allocator_traits<malloc_allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, these should not give errors:
+constexpr bool c = has_construct<malloc_allocator<NoDefault>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<malloc_allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<malloc_allocator<NoDest>, NoDest>::value;
+constexpr bool b2 = has_traits_destroy<malloc_allocator<int>, NoDest>::value;
+
+malloc_allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );

diff --git a/libstdc++-v3/testsuite/ext/new_allocator/89510.cc b/libstdc++-v3/testsuite/ext/new_allocator/89510.cc
new file mode 100644 (file)
index 0000000..f684a9c
--- /dev/null
+++ b/libstdc++-v3/testsuite/ext/new_allocator/89510.cc
@@ -0,0 +1,149 @@
+// 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 <ext/new_allocator.h>
+#include <memory>
+#include <type_traits>
+
+using __gnu_cxx::new_allocator;
+using AT = std::allocator_traits<new_allocator<int>>;
+
+template<typename...> using void_t = void;
+
+template<typename T, typename U, typename = void>
+struct has_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_construct<T, U,
+    void_t<decltype(std::declval<T&>().construct(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_destroy<T, U,
+    void_t<decltype(std::declval<T&>().destroy(std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_construct
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_construct<T, U,
+    void_t<decltype(AT::construct(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+template<typename T, typename U, typename = void>
+struct has_traits_destroy
+: std::false_type
+{ };
+
+template<typename T, typename U>
+struct has_traits_destroy<T, U,
+    void_t<decltype(AT::destroy(std::declval<T&>(), std::declval<U*>()))>>
+: std::true_type
+{ };
+
+struct NoDefault { NoDefault(int); };
+struct NoDest { private: ~NoDest(); };
+
+// Whether true or false, these should not give errors:
+constexpr bool c = has_construct<new_allocator<NoDefault>, NoDefault>::value;
+constexpr bool c2 = has_traits_construct<new_allocator<int>, NoDefault>::value;
+constexpr bool d = has_destroy<new_allocator<NoDest>, NoDest>::value;
+constexpr bool d2 = has_traits_destroy<new_allocator<int>, NoDest>::value;
+
+new_allocator<int> a;
+
+long* lp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(lp)), "" );
+static_assert( noexcept(a.construct(lp, 1L)), "" );
+static_assert( noexcept(a.construct(lp, 2)), "" );
+static_assert( noexcept(a.construct(lp, 2U)), "" );
+static_assert( noexcept(a.destroy(lp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, lp)), "" );
+static_assert( noexcept(AT::construct(a, lp, 1L)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2)), "" );
+static_assert( noexcept(AT::construct(a, lp, 2U)), "" );
+static_assert( noexcept(AT::destroy(a, lp)), "" );
+
+struct X
+{
+  X() noexcept;
+  X(int) noexcept;
+  ~X() noexcept;
+};
+
+X* xp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(xp)), "" );
+static_assert( noexcept(a.construct(xp, 1)), "" );
+static_assert( noexcept(a.destroy(xp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, xp)), "" );
+static_assert( noexcept(AT::construct(a, xp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, xp)), "" );
+
+struct Y
+{
+  Y() noexcept;
+  Y(int) noexcept(false);
+  ~Y() noexcept;
+};
+
+Y* yp;
+#if __cplusplus <= 201703L
+static_assert( noexcept(a.construct(yp)), "" );
+static_assert( ! noexcept(a.construct(yp, 1)), "" );
+static_assert( noexcept(a.destroy(yp)), "" );
+#endif
+static_assert( noexcept(AT::construct(a, yp)), "" );
+static_assert( ! noexcept(AT::construct(a, yp, 1)), "" );
+static_assert( noexcept(AT::destroy(a, yp)), "" );
+
+struct Z
+{
+  Z() noexcept;
+  Z(int) noexcept;
+  ~Z() noexcept(false);
+};
+
+Z* zp;
+// These construct calls should be noexcept, but they are false because
+// they use is_nothrow_constructible which depends on is_nothrow_destructible.
+#if __cplusplus <= 201703L
+static_assert( ! noexcept(a.construct(zp)), "wrong" );
+static_assert( ! noexcept(a.construct(zp, 1)), "wrong" );
+static_assert( ! noexcept(a.destroy(zp)), "" );
+#endif
+static_assert( ! noexcept(AT::construct(a, zp)), "" );
+static_assert( ! noexcept(AT::construct(a, zp, 1)), "" );
+static_assert( ! noexcept(AT::destroy(a, zp)), "" );