remove boost demangle

[psychocoderHPC]

https://github.com/alpaka-group/alpaka/blob/e20236d86be9a8093fa2efae44eaf2db79dc38db/include/alpaka/core/DemangleTypeNames.hpp#L18-L19

We aim to remove boost completely. With clang 15+ and gcc 11+ we can remove this code with the following code. These versions support std::source_location.

#include <source_location>
#include <string>
#include <string_view>
    /// \file
    /// use source_location to derive the demangled type name
    /// based on:
    /// https://www.reddit.com/r/cpp/comments/lfi6jt/finally_a_possibly_portable_way_to_convert_types/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

    struct DummyType
    {
    };

    template<typename T>
    inline auto EmbedTypeIntoSignature()
    {
        return std::string_view{std::source_location::current().function_name()};
    }

    template<typename T>
    struct Demangled
    {
        static auto name()
        {
            constexpr size_t testSignatureLength = sizeof("DummyType") - 1;
            auto const DummySignature = EmbedTypeIntoSignature<DummyType>();
            // count char's until the type name starts
            auto const startPosition = DummySignature.find("DummyType");
            // count char's after the type information by removing type name information and pre information
            auto const tailLength = DummySignature.size() - startPosition - testSignatureLength;
            auto const EmbeddingSignature = EmbedTypeIntoSignature<T>();
            auto const typeLength = EmbeddingSignature.size() - startPosition - tailLength;
            return EmbeddingSignature.substr(startPosition, typeLength);
        }
    };

    template<typename T>
    auto demangled = Demangled<T>::name();

[fwyzard]

Can it be constexpr ?

[fwyzard]

In general, I do not share the "remove boost at all costs" goal, so to me the new implementation needs to be at least as good as the old one, or possibly better.

[SimeonEhrig]

std::source_location::current() is actual pretty well. I think it is more a question if we want remove the compilers, which does not support std::source_location::current().

[SimeonEhrig]

@fwyzard If you want, you can test it here: https://godbolt.org/z/P6MsrKTKv

Update: a more advanced example with namespace: https://godbolt.org/z/159Gs313h

[SimeonEhrig]

Can it be constexpr ?

Yes. My minimal example produces only 15 lines assembler including printing: https://godbolt.org/z/YhxKx6n3W (looks like there is a small bug with the string termination symbol \0).