1 // boost polymorphic_cast.hpp header file ----------------------------------------------//
3 // (C) Copyright Kevlin Henney and Dave Abrahams 1999.
4 // (C) Copyright Boris Rasin 2014.
5 // Distributed under the Boost
6 // Software License, Version 1.0. (See accompanying file
7 // LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
9 // See http://www.boost.org/libs/conversion for Documentation.
12 // 10 Nov 14 polymorphic_pointer_downcast moved to a separate header,
13 // minor improvements to stisfy latest Boost coding style
14 // 08 Nov 14 Add polymorphic_pointer_downcast (Boris Rasin)
15 // 09 Jun 14 "cast.hpp" was renamed to "polymorphic_cast.hpp" and
16 // inclusion of numeric_cast was removed (Antony Polukhin)
17 // 23 Jun 05 numeric_cast removed and redirected to the new verion (Fernando Cacciola)
18 // 02 Apr 01 Removed BOOST_NO_LIMITS workarounds and included
19 // <boost/limits.hpp> instead (the workaround did not
20 // actually compile when BOOST_NO_LIMITS was defined in
21 // any case, so we loose nothing). (John Maddock)
22 // 21 Jan 01 Undid a bug I introduced yesterday. numeric_cast<> never
23 // worked with stock GCC; trying to get it to do that broke
25 // 20 Jan 01 Moved BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS to config.hpp.
26 // Removed unused BOOST_EXPLICIT_TARGET macro. Moved
27 // boost::detail::type to boost/type.hpp. Made it compile with
28 // stock gcc again (Dave Abrahams)
29 // 29 Nov 00 Remove nested namespace cast, cleanup spacing before Formal
30 // Review (Beman Dawes)
31 // 19 Oct 00 Fix numeric_cast for floating-point types (Dave Abrahams)
32 // 15 Jul 00 Suppress numeric_cast warnings for GCC, Borland and MSVC
34 // 30 Jun 00 More MSVC6 wordarounds. See comments below. (Dave Abrahams)
35 // 28 Jun 00 Removed implicit_cast<>. See comment below. (Beman Dawes)
36 // 27 Jun 00 More MSVC6 workarounds
37 // 15 Jun 00 Add workarounds for MSVC6
38 // 2 Feb 00 Remove bad_numeric_cast ";" syntax error (Doncho Angelov)
39 // 26 Jan 00 Add missing throw() to bad_numeric_cast::what(0 (Adam Levar)
40 // 29 Dec 99 Change using declarations so usages in other namespaces work
41 // correctly (Dave Abrahams)
42 // 23 Sep 99 Change polymorphic_downcast assert to also detect M.I. errors
43 // as suggested Darin Adler and improved by Valentin Bonnard.
44 // 2 Sep 99 Remove controversial asserts, simplify, rename.
45 // 30 Aug 99 Move to cast.hpp, replace value_cast with numeric_cast,
46 // place in nested namespace.
47 // 3 Aug 99 Initial version
49 #ifndef BOOST_POLYMORPHIC_CAST_HPP
50 #define BOOST_POLYMORPHIC_CAST_HPP
52 # include <boost/config.hpp>
53 # include <boost/assert.hpp>
54 # include <boost/throw_exception.hpp>
57 #ifdef BOOST_HAS_PRAGMA_ONCE
63 // See the documentation for descriptions of how to choose between
64 // static_cast<>, dynamic_cast<>, polymorphic_cast<> and polymorphic_downcast<>
66 // polymorphic_cast --------------------------------------------------------//
68 // Runtime checked polymorphic downcasts and crosscasts.
69 // Suggested in The C++ Programming Language, 3rd Ed, Bjarne Stroustrup,
70 // section 15.8 exercise 1, page 425.
72 template <class Target, class Source>
73 inline Target polymorphic_cast(Source* x)
75 Target tmp = dynamic_cast<Target>(x);
76 if ( tmp == 0 ) boost::throw_exception( std::bad_cast() );
80 // polymorphic_downcast ----------------------------------------------------//
82 // BOOST_ASSERT() checked polymorphic downcast. Crosscasts prohibited.
84 // WARNING: Because this cast uses BOOST_ASSERT(), it violates
85 // the One Definition Rule if used in multiple translation units
86 // where BOOST_DISABLE_ASSERTS, BOOST_ENABLE_ASSERT_HANDLER
87 // NDEBUG are defined inconsistently.
89 // Contributed by Dave Abrahams
91 template <class Target, class Source>
92 inline Target polymorphic_downcast(Source* x)
94 BOOST_ASSERT( dynamic_cast<Target>(x) == x ); // detect logic error
95 return static_cast<Target>(x);
100 #endif // BOOST_POLYMORPHIC_CAST_HPP