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libstdc++: Fix std::common_iterator triviality [PR100823]

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This fixes the remaining problem reported in the PR, that the special
members should be trivial.  This can be done by constraining the
non-trivial versions and adding defaulted overloads that will be used
when the union members are trivial.

Making these members trivial alters the argument passing ABI and so
isn't suitable for backporting to release branches.

libstdc++-v3/ChangeLog:

	PR libstdc++/100823
	* include/bits/stl_iterator.h (common_iterator): Define
	destructor, copy constructor and move constructor as trivial
	when the underlying types allow.
	* testsuite/24_iterators/common_iterator/100823.cc: Check
	triviality of special members.
This commit is contained in:
Jonathan Wakely 2022-07-20 16:51:44 +01:00
parent 56c999860b
commit 87a9bfe86d
2 changed files with 30 additions and 0 deletions
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15
libstdc++-v3/include/bits/stl_iterator.h
View file

@ -1925,9 +1925,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
}
common_iterator(const common_iterator&) = default;
constexpr
common_iterator(const common_iterator& __x)
noexcept(_S_noexcept<const _It&, const _Sent&>())
requires (!is_trivially_copyable_v<_It> || !is_trivially_copyable_v<_Sent>)
: _M_valueless(), _M_index(__x._M_index)
{
if (_M_index == 0)
@ -1946,9 +1949,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
}
common_iterator(common_iterator&&) = default;
constexpr
common_iterator(common_iterator&& __x)
noexcept(_S_noexcept<_It, _Sent>())
requires (!is_trivially_copyable_v<_It> || !is_trivially_copyable_v<_Sent>)
: _M_valueless(), _M_index(__x._M_index)
{
if (_M_index == 0)
@ -2017,8 +2023,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
return *this;
}
#if __cpp_concepts >= 202002L // Constrained special member functions
~common_iterator() = default;
constexpr
~common_iterator()
requires (!is_trivially_destructible_v<_It>
|| !is_trivially_destructible_v<_Sent>)
#else
constexpr
~common_iterator()
#endif
{
if (_M_index == 0)
_M_it.~_It();

15
libstdc++-v3/testsuite/24_iterators/common_iterator/100823.cc
View file

@ -4,6 +4,21 @@
#include <testsuite_iterators.h>
#include <testsuite_hooks.h>
void
test_triviality()
{
using I = std::common_iterator<int*, const int*>;
// Cannot be trivial, because it has to initialize members.
static_assert( ! std::is_trivially_default_constructible_v<I> );
static_assert( std::is_trivially_destructible_v<I> );
static_assert( std::is_trivially_copy_constructible_v<I> );
static_assert( std::is_trivially_copy_assignable_v<I> );
static_assert( std::is_trivially_move_constructible_v<I> );
static_assert( std::is_trivially_move_assignable_v<I> );
}
void
test_valueless_assignment()
{