Function to print c++ type names as plain text in gcc and clang

demangle.hpp

#ifndef UT_DEMANGLE_HPP
#define UT_DEMANGLE_HPP

/// Get type name as a string

/* Usage:
 * #include "demangle.hpp"
 * #include <iostream>
 *
 * namespace A::B {
 * inline namespace C {
 *     struct S { };
 *
 *     template<typename>
 *     struct Wrap { };
 *
 *     template<template<class> class>
 *     struct WrapWrap { };
 *
 *     class Base { public: virtual ~Base() = default; };
 *     class Derived : public Base { };
 *
 * }  // namespace C
 * }  // namespace A::B
 *
 * int main() {
 *     using namespace A::B;
 *     WrapWrap<Wrap> const a;
 *     Base b {};
 *     Derived d {};
 *     Base &b_ref = b;
 *     Base const&d_ref = d;
 *
 *     std::cout
 *         << "dynamic mangled:   " << typeid(a).name()                << '\n'
 *         << "dynamic demangled: " << ut::typeNameDynamic(a)          << '\n'
 *         << "static demangled:  " << ut::typeName<decltype(a)>()     << '\n'
 *         << "____________________________________________________________\n"
 *         << "dynamic mangled:   " << typeid(b_ref).name()            << '\n'
 *         << "dynamic demangled: " << ut::typeNameDynamic(b_ref)      << '\n'
 *         << "static demangled:  " << ut::typeName<decltype(b_ref)>() << '\n'
 *         << "____________________________________________________________\n"
 *         << "dynamic mangled:   " << typeid(d_ref).name()            << '\n'
 *         << "dynamic demangled: " << ut::typeNameDynamic(d_ref)      << '\n'
 *         << "static demangled:  " << ut::typeName<decltype(d_ref)>() << '\n'
 *         ;
 * }
 *
 * // Possible output:
 * //   dynamic mangled:   N1A1B1C8WrapWrapINS1_4WrapEEE
 * //   dynamic demangled: A::B::C::WrapWrap<A::B::C::Wrap>
 * //   static demangled:  const A::B::C::WrapWrap<A::B::C::Wrap>
 * //   ____________________________________________________________
 * //   dynamic mangled:   N1A1B1C4BaseE
 * //   dynamic demangled: A::B::C::Base
 * //   static demangled:  A::B::C::Base&
 * //   ____________________________________________________________
 * //   dynamic mangled:   N1A1B1C7DerivedE
 * //   dynamic demangled: A::B::C::Derived
 * //   static demangled:  const A::B::C::Base&
 *
 */

#ifdef __GNUC__  // GCC and Clang
#    include <cxxabi.h>
#endif


#include <memory>
#include <source_location>
#include <stdexcept>
#include <string>
#include <string_view>

namespace ut {

namespace detail {
    template<typename T>
    consteval char const *getTypeName() {
        return std::source_location::current().function_name();
    }
}

/** Get the static type as a compile time string_view
 *
 * Preserves `const`, `volatile` and reference qualifiers
 */
template<typename T>
consteval std::string_view typeName() {
    std::string_view const type_name = detail::getTypeName<T>();
    auto const open_pos = [&] {
        if (auto clang_pos = type_name.find("[T = "); clang_pos != type_name.npos)
            return clang_pos + 5;
        else if (auto gcc_pos = type_name.find("[with T = "); gcc_pos != type_name.npos)
            return gcc_pos + 10;
        else
            return type_name.npos;
    }();
    if (open_pos != type_name.npos) {  // gcc and clang
        auto const close_pos = type_name.find(']');
        if (close_pos == type_name.npos) throw std::logic_error("Could not parse end of type (GCC,Clang)");
        return type_name.substr(open_pos, close_pos - open_pos);
    } else {  // msvc
        auto const type_name_open = type_name.find('<') + 1;
        auto const type_name_close = type_name.find(">(void)") + 1;
        if (type_name_open == type_name.npos) throw std::logic_error("Could not parse start of type (MSVC)");
        if (type_name_close == type_name.npos) throw std::logic_error("Could not parse end of type (MSVC)");
        return type_name.substr(type_name_open, type_name_close - type_name_open);
    }
}

/* Return the dynamic type of `val` as a string
 *
 * NOTE: `const`, `volatile` and reference qualifiers will be discarded
 *
 * @throws: `std::bad_alloc`
 * @throws: `std::runtime_error`
 */
template<typename T>
[[nodiscard]]
std::string typeNameDynamic(T const &val);

#ifdef __GNUC__  // GCC and Clang
template<typename T>
[[nodiscard]]
std::string typeNameDynamic(T const &val) {
    auto const *name = typeid(val).name();
    int status = 1;
    std::unique_ptr<char, decltype(&std::free)> realname {
        abi::__cxa_demangle(name, nullptr, nullptr, &status),
        std::free,
    };
    switch (status) {
        case 0: break;
        case -1: throw std::bad_alloc();
        case -2: return name;
        case -3: throw std::runtime_error("Demangling failed due to an internal error");
        default: throw std::runtime_error("Unexpected exit code from __cxa_demangle: " + std::to_string(status));
    }

    if (realname)
        return realname.get();
    else
        throw std::runtime_error("Demangling failed. Status: " + std::to_string(status));
}


#else  // other compilers. This will return a platform specific string (on MSVC this is the demangled name)
template<typename T>
[[nodiscard]]
std::string typeNameDynamic(T const &val) {
    return typeid(val).name();
}
#endif
}  // namespace ut

/*
This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <https://unlicense.org>
*/

#endif  // UT_DEMANGLE_HPP

zzz_description

convert types into human readable strings