https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117962
Bug ID: 117962
Summary: Debug Mode containers with stateful allocators don't
work in constexpr
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: rejects-valid
Severity: normal
Priority: P3
Component: libstdc++
Assignee: unassigned at gcc dot gnu.org
Reporter: redi at gcc dot gnu.org
Target Milestone: ---
This fails with -std=c++20 -D_GLIBCXX_DEBUG
#include <memory>
#include <vector>
template<typename T>
struct Alloc : std::allocator<T>
{
using std::allocator<T>::allocator;
constexpr explicit Alloc(int p) : personality(p) { }
template<typename U>
constexpr Alloc(const Alloc<U>& a) : personality(a.personality) { }
using is_always_equal = std::false_type;
int personality = 0;
constexpr bool operator==(const Alloc& a) const noexcept
{ return personality == a.personality; }
};
constexpr bool
move_constructor()
{
std::vector<long, Alloc<long>> l1;
std::vector<long, Alloc<long>> l2(std::move(l1), l1.get_allocator());
return true;
}
static_assert( move_constructor() );
debug/safe_container.h:68:25: error: call to non-'constexpr' function 'void
__gnu_debug::_Safe_sequence_base::_M_swap(__gnu_debug::_Safe_sequence_base&)'
68 | _Base::_M_swap(__x);
| ~~~~~~~~~~~~~~^~~~~
That _M_swap function can't be constexpr unless we move its definition inline,
as it's currently in src/c++11/debug.o
Maybe the allocator-extended move constructor that uses _M_swap could be
re-specified in terms of move assignment of the base subobject.
