[Bug libstdc++/53657] [C++11] pair(pair&&) move constructor is non-trivial
paolo.carlini at oracle dot com
gcc-bugzilla@gcc.gnu.org
Thu Jun 14 09:41:00 GMT 2012
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53657
Richard Guenther <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work| |4.5.1, 4.6.0
Target Milestone|--- |4.7.2
Summary|[C++11] pair(pair&&) move |[4.7/4.8 Regression][C++11]
|constructor is non-trivial |pair(pair&&) move
| |constructor is non-trivial
Known to fail| |4.5.0
Paolo Carlini <paolo.carlini at oracle dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Known to work|4.5.1, 4.6.0 |
Target Milestone|4.7.2 |---
Summary|[4.7/4.8 Regression][C++11] |[C++11] pair(pair&&) move
|pair(pair&&) move |constructor is non-trivial
|constructor is non-trivial |
Known to fail|4.5.0 |
--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-06-14 09:39:58 UTC ---
Thanks.
--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-06-14 09:40:44 UTC ---
The issue is related to LWG2005, and can be summarized with the following
testcase, which should not trigger the static_assert.
In short, if we want std::pair' move constructor defaulted, we have to use
std::is_constructible, not std::is_convertible, to constrain container::insert.
If people agree with my assessment - I don't see what else we could possibly do
on the library side - I can try again moving the latter to use
std::is_constructible, should mostly work.
/////////////////
#include <type_traits>
#include <utility>
struct move_only
{
move_only(const move_only&) = delete;
move_only(move_only&&) = default;
};
template<typename _T1, typename _T2>
struct pair
{
pair(pair&&) = default;
template<class _U1, class _U2>
pair(pair<_U1, _U2>&& __p)
: first(std::forward<_U1>(__p.first)),
second(std::forward<_U2>(__p.second)) { }
_T1 first;
_T2 second;
};
typedef pair<move_only, move_only> Pair;
typedef pair<const move_only, move_only> CPair;
static_assert(std::is_convertible<Pair, CPair>::value, "Error");
//static_assert(std::is_constructible<CPair, Pair&&>::value, "Error");
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