Re: (Boost) Reflecto

On Tue, Apr 7, 2026 at 3:12 AM Alexander Grund via Boost <
[email protected]> wrote:

> Am 06.04.26 um 17:07 schrieb Emil Dotchevski via Boost:
> > - enum_value_names<E> returns a constexpr array of name/value pairs (like
> > Describe does for described enums) that includes only the named values;
> > there is also named_enum_value_count and min_/max_named_enum_value.
> That sounds like a heavy footgun: You can always get the name of an
> enumerator / all enumerators , except when you cannot.
> For name<->enumerator conversions you could throw/static_assert to
> detect this case.
> For try-to-name like functions you cannot.
>

For runtime lookups, the returned name object can be checked to see if the
lookup was successful. That's the best behavior possible (it is not
undefined behavior).


> This is amplified by this being a define
> (BOOST_REFLECTO_DEFAULT_ENUM_MIN_VALUE):
> When someone (e.g. a consumer of your library built on reflecto) has
> already included reflecto and/or defined those then your code will
> suddenly break
>

This is a very good point and it inspired me to find a solution. Now the
enum_lookup_range can be specified for all enums within a given namespace,
not just for individual enums:

namespace lib1
{
    struct this_namespace;

    enum class some_enum { .... };
}

namespace boost::reflecto
{
    template <>
    struct enum_lookup_range<specialize_for_namespace<lib1::this_namespace>>
    {
        // specialization applies for any enum within the namespace lib1,
        // including lib1::some_enum.
    };
}

I made this machinery part of the public API in meta_specialization.hpp, so
the ability to look up a template specialization based on the namespace of
some type is universally available, see
https://github.com/zajo/reflecto?tab=readme-ov-file#meta-specialization.
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