update source to Ceph Pacific 16.2.2

[ceph.git] / ceph / src / boost / boost / outcome / experimental / status-code / error.hpp

/* Proposed SG14 status_code
(C) 2018-2020 Niall Douglas <http://www.nedproductions.biz/> (5 commits)
File Created: Feb 2018


Boost Software License - Version 1.0 - August 17th, 2003

Permission is hereby granted, free of charge, to any person or organization
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*/

#ifndef BOOST_OUTCOME_SYSTEM_ERROR2_ERROR_HPP
#define BOOST_OUTCOME_SYSTEM_ERROR2_ERROR_HPP

#include "errored_status_code.hpp"
#include "system_code.hpp"

BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_BEGIN

/*! An erased `system_code` which is always a failure. The closest equivalent to
`std::error_code`, except it cannot be null and cannot be modified.

This refines `system_code` into an `error` object meeting the requirements of
[P0709 Zero-overhead deterministic exceptions](https://wg21.link/P0709).

Differences from `system_code`:

- Always a failure (this is checked at construction, and if not the case,
the program is terminated as this is a logic error)
- No default construction.
- No empty state possible.
- Is immutable.

As with `system_code`, it remains guaranteed to be two CPU registers in size,
and move bitcopying.
*/
using error = errored_status_code<erased<system_code::value_type>>;

#ifndef NDEBUG
static_assert(sizeof(error) == 2 * sizeof(void *), "error is not exactly two pointers in size!");
static_assert(traits::is_move_bitcopying<error>::value, "error is not move bitcopying!");
#endif

BOOST_OUTCOME_SYSTEM_ERROR2_NAMESPACE_END

#endif