On 24/10/19 15:31 +0100, Jonathan Wakely wrote:
On 23/10/19 20:27 +0100, Jonathan Wakely wrote:
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -154,13 +154,42 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX20_CONSTEXPR
allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
+#if __cplusplus <= 201703L
~allocator() _GLIBCXX_NOTHROW { }
+#endif
This changes the value of is_trivially_destructible_v<allocator<T>> so
maybe it would be better to keep the user-provided destructor but make
it constexpr:
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -154,9 +154,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX20_CONSTEXPR
allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
-#if __cplusplus <= 201703L
+ _GLIBCXX20_CONSTEXPR
~allocator() _GLIBCXX_NOTHROW { }
-#endif
#if __cplusplus > 201703L
[[nodiscard,__gnu__::__always_inline__]]
With the earlier commit r277300 I've still changed the result of
is_trivially_destructible_v<allocator<void>> and
is_trivially_*_constructible_v<allocator<void>> because the
allocator<void> explicit specialization no longer exists for C++20.
That might be a bigger problem.
This restores the previous properties of std::allocator.
Tested powerpc64le-linux, committed to trunk.
commit 29d60b4d998ba2678da4ef8417ef58f5373cad8b
Author: Jonathan Wakely <jwak...@redhat.com>
Date: Thu Oct 24 15:52:57 2019 +0100
Revert ABI changes to std::allocator in C++20
The recent C++20 changes to remove the std::allocator<void> explicit
specialization and the destructor in the std::allocator primary template
change the result of some is_trivially_xxx type traits. To avoid those
changes, this patch restores the explicit specialization and the
destructor.
In order to meet the C++20 requirements the std::allocator<void>
explicit specialization must provide the same interface as the primary
template (except for the unusable allocate and deallocate member
functions) and the destructor in the primary template must be constexpr.
* include/bits/allocator.h (allocator<void>): Restore the explicit
specialization for C++20, but make its API consistent with the primary
template.
(allocator::~allocator()): Restore the destructor for C++20, but make
it constexpr.
* testsuite/20_util/allocator/rebind_c++20.cc: Check allocator<void>.
* testsuite/20_util/allocator/requirements/typedefs_c++20.cc: Likewise.
* testsuite/20_util/allocator/void.cc: Check that constructors and
destructors are trivial. Check for converting constructor in C++20.
* testsuite/ext/malloc_allocator/variadic_construct.cc: Simplify
dejagnu target selector.
* testsuite/ext/new_allocator/variadic_construct.cc: Likewise.
diff --git a/libstdc++-v3/include/bits/allocator.h b/libstdc++-v3/include/bits/allocator.h
index 1a3eb88eded..2559c57b12e 100644
--- a/libstdc++-v3/include/bits/allocator.h
+++ b/libstdc++-v3/include/bits/allocator.h
@@ -63,23 +63,30 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @{
*/
-#if __cplusplus <= 201703L
/// allocator<void> specialization.
template<>
class allocator<void>
{
public:
+ typedef void value_type;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
+#if __cplusplus <= 201703L
typedef void* pointer;
typedef const void* const_pointer;
- typedef void value_type;
template<typename _Tp1>
struct rebind
{ typedef allocator<_Tp1> other; };
+#else
+ allocator() = default;
-#if __cplusplus >= 201103L
+ template<typename _Up>
+ constexpr
+ allocator(const allocator<_Up>&) { }
+#endif // ! C++20
+
+#if __cplusplus >= 201103L && __cplusplus <= 201703L
// _GLIBCXX_RESOLVE_LIB_DEFECTS
// 2103. std::allocator propagate_on_container_move_assignment
typedef true_type propagate_on_container_move_assignment;
@@ -98,9 +105,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
destroy(_Up* __p)
noexcept(noexcept(__p->~_Up()))
{ __p->~_Up(); }
-#endif // C++11
+#endif // C++11 to C++17
};
-#endif // ! C++20
/**
* @brief The @a standard allocator, as per [20.4].
@@ -154,9 +160,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
_GLIBCXX20_CONSTEXPR
allocator(const allocator<_Tp1>&) _GLIBCXX_NOTHROW { }
-#if __cplusplus <= 201703L
+ _GLIBCXX20_CONSTEXPR
~allocator() _GLIBCXX_NOTHROW { }
-#endif
#if __cplusplus > 201703L
[[nodiscard,__gnu__::__always_inline__]]
diff --git a/libstdc++-v3/testsuite/20_util/allocator/rebind_c++20.cc b/libstdc++-v3/testsuite/20_util/allocator/rebind_c++20.cc
index 968e1de931b..dd7cd67f943 100644
--- a/libstdc++-v3/testsuite/20_util/allocator/rebind_c++20.cc
+++ b/libstdc++-v3/testsuite/20_util/allocator/rebind_c++20.cc
@@ -23,6 +23,9 @@
template<typename T> struct Alloc : std::allocator<T> { };
using T = std::allocator_traits<Alloc<int>>;
-
// Prior to C++20 this finds std::allocator<int>::rebind and so fails:
static_assert( std::is_same_v<T::rebind_alloc<long>, Alloc<long>> );
+
+using V = std::allocator_traits<Alloc<void>>;
+// Prior to C++20 this finds std::allocator<void>::rebind and so fails:
+static_assert( std::is_same_v<V::rebind_alloc<long>, Alloc<long>> );
diff --git a/libstdc++-v3/testsuite/20_util/allocator/requirements/typedefs_c++20.cc b/libstdc++-v3/testsuite/20_util/allocator/requirements/typedefs_c++20.cc
index e986cc9a809..ef193fb1bf1 100644
--- a/libstdc++-v3/testsuite/20_util/allocator/requirements/typedefs_c++20.cc
+++ b/libstdc++-v3/testsuite/20_util/allocator/requirements/typedefs_c++20.cc
@@ -54,3 +54,14 @@ static_assert( !has_rebind<A> );
static_assert( !has_construct<A> );
static_assert( !has_destroy<A> );
static_assert( !has_max_size<A> );
+
+using V = std::allocator<void>;
+
+static_assert( !has_pointer<V> );
+static_assert( !has_const_pointer<V> );
+static_assert( !has_reference<V> );
+static_assert( !has_const_reference<V> );
+static_assert( !has_rebind<V> );
+static_assert( !has_construct<V> );
+static_assert( !has_destroy<V> );
+static_assert( !has_max_size<V> );
diff --git a/libstdc++-v3/testsuite/20_util/allocator/void.cc b/libstdc++-v3/testsuite/20_util/allocator/void.cc
index d7aa6bd80ed..9d94fac3cc0 100644
--- a/libstdc++-v3/testsuite/20_util/allocator/void.cc
+++ b/libstdc++-v3/testsuite/20_util/allocator/void.cc
@@ -33,6 +33,28 @@ test01()
std::allocator_traits<alloc_type>::destroy(a, &i);
}
+// These properties are formally unspecified, but have always been true for
+// the libstdc++ definition of allocator<void>.
+static_assert(
+ std::is_trivially_default_constructible<std::allocator<void>>::value,
+ "explicit specialization has trivial default constructor");
+static_assert(
+ std::is_trivially_copy_constructible<std::allocator<void>>::value,
+ "explicit specialization has trivial copy constructor");
+static_assert(
+ std::is_trivially_move_constructible<std::allocator<void>>::value,
+ "explicit specialization has trivial move constructor");
+static_assert(
+ std::is_trivially_destructible<std::allocator<void>>::value,
+ "explicit specialization has trivial destructor");
+
+#if __cplusplus > 201703L
+// C++20 removes the allocator<void> explicit specialization, so it can now be
+// constructed using the converting constructor from other specializations.
+static_assert( std::is_constructible_v<std::allocator<void>,
+ std::allocator<int>> );
+#endif
+
int
main()
{
diff --git a/libstdc++-v3/testsuite/ext/malloc_allocator/variadic_construct.cc b/libstdc++-v3/testsuite/ext/malloc_allocator/variadic_construct.cc
index b786fae9f0a..f122768d8ac 100644
--- a/libstdc++-v3/testsuite/ext/malloc_allocator/variadic_construct.cc
+++ b/libstdc++-v3/testsuite/ext/malloc_allocator/variadic_construct.cc
@@ -1,4 +1,4 @@
-// { dg-do run { target { { c++11_only || c++14_only } || c++17_only } } }
+// { dg-do run { target { c++11 && { ! c++2a } } } }
// 2007-10-26 Paolo Carlini <pcarl...@suse.de>
diff --git a/libstdc++-v3/testsuite/ext/new_allocator/variadic_construct.cc b/libstdc++-v3/testsuite/ext/new_allocator/variadic_construct.cc
index 5b23e5b4a2c..cfe93a7b6d9 100644
--- a/libstdc++-v3/testsuite/ext/new_allocator/variadic_construct.cc
+++ b/libstdc++-v3/testsuite/ext/new_allocator/variadic_construct.cc
@@ -1,4 +1,4 @@
-// { dg-do run { target { { c++11_only || c++14_only } || c++17_only } } }
+// { dg-do run { target { c++11 && { ! c++2a } } } }
// 2007-10-26 Paolo Carlini <pcarl...@suse.de>
