Boost C++ Libraries

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Chapter 39. Boost.TypeIndex 4.2

Chapter 39. Boost.TypeIndex 4.2

Copyright © 2012-2025 Antony Polukhin

Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

Table of Contents

Getting started

How to use
Example with Boost.Any
Example with Boost.Variant

Configuring and building the library

How it works

Getting human readable and mangled type names
Storing information about a type in container
Getting through the inheritance to receive a real type name
Using runtime_cast where RTTI is unavailable or undesirable
Exact type matching: storing type with const, volatile and reference qualifiers
Table of raw_name() and pretty_name() outputs with and without RTTI
C++14: Checking namespace at compile time
C++14: Checking lexigraphical order of provided types

Boost.TypeIndex Header Reference

Header <boost/type_index.hpp>
Header <boost/type_index/ctti_type_index.hpp>
Header <boost/type_index/runtime_cast.hpp>
Header <boost/type_index/runtime_cast/boost_shared_ptr_cast.hpp>
Header <boost/type_index/runtime_cast/pointer_cast.hpp>
Header <boost/type_index/runtime_cast/reference_cast.hpp>
Header <boost/type_index/runtime_cast/register_runtime_class.hpp>
Header <boost/type_index/runtime_cast/std_shared_ptr_cast.hpp>
Header <boost/type_index/stl_type_index.hpp>
Header <boost/type_index/type_index_facade.hpp>

Making a custom type_index

Basics
Getting type infos at runtime
Using new type infos all around the code

C++20 module

Space and Performance

RTTI emulation limitations

Define the BOOST_TYPE_INDEX_FUNCTION_SIGNATURE macro
Fixing pretty_name() output

Mixing sources with RTTI on and RTTI off

Acknowledgements

Motivation

Sometimes getting and storing information about a type at runtime is required. For such cases a construction like &typeid(T) or C++11 class std::type_index is usually used, which is where problems start:

typeid(T) and std::type_index require Run Time Type Info (RTTI)
some implementations of typeid(T) erroneously do not strip const, volatile and references from type
some compilers have bugs and do not correctly compare std::type_info objects across shared libraries
only a few implementations of Standard Library currently provide std::type_index
no easy way to store type info without stripping const, volatile and references
no nice and portable way to get human readable type names
no way to easily make your own type info class

Boost.TypeIndex library was designed to work around all those issues.

	Note
	`T` means type here. Think of it as of `T` in `template <class T>`