system/detail/throws.hpp

0001 #ifndef BOOST_SYSTEM_DETAIL_THROWS_HPP_INCLUDED
0002 #define BOOST_SYSTEM_DETAIL_THROWS_HPP_INCLUDED
0003
0004 //  Copyright Beman Dawes 2006, 2007
0005 //  Copyright Christoper Kohlhoff 2007
0006 //  Copyright Peter Dimov 2017, 2018
0007 //
0008 //  Distributed under the Boost Software License, Version 1.0. (See accompanying
0009 //  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0010 //
0011 //  See library home page at http://www.boost.org/libs/system
0012
0013 namespace boost
0014 {
0015
0016 namespace system
0017 {
0018
0019 class error_code;
0020
0021 } // namespace system
0022
0023 // boost::throws()
0024
0025 namespace detail
0026 {
0027
0028 //  Misuse of the error_code object is turned into a noisy failure by
0029 //  poisoning the reference. This particular implementation doesn't
0030 //  produce warnings or errors from popular compilers, is very efficient
0031 //  (as determined by inspecting generated code), and does not suffer
0032 //  from order of initialization problems. In practice, it also seems
0033 //  cause user function error handling implementation errors to be detected
0034 //  very early in the development cycle.
0035
0036 inline system::error_code* throws()
0037 {
0038     // See github.com/boostorg/system/pull/12 by visigoth for why the return
0039     // is poisoned with nonzero rather than (0). A test, test_throws_usage(),
0040     // has been added to error_code_test.cpp, and as visigoth mentioned it
0041     // fails on clang for release builds with a return of 0 but works fine
0042     // with (1).
0043     // Since the undefined behavior sanitizer (-fsanitize=undefined) does not
0044     // allow a reference to be formed to the unaligned address of (1), we use
0045     // (8) instead.
0046
0047     return reinterpret_cast<system::error_code*>(8);
0048 }
0049
0050 } // namespace detail
0051
0052 inline system::error_code& throws()
0053 {
0054     return *detail::throws();
0055 }
0056
0057 } // namespace boost
0058
0059 #endif // #ifndef BOOST_SYSTEM_DETAIL_THROWS_HPP_INCLUDED