Preprocessor Usage

[andrewkcorcoran]

Various third party libraries provide preprocessor macros that process enum values. A classic example is for serializing and deserializing enums.

namespace ns { enum class MyEnum{ A, B, C, D, E, F, G, H}; }
SERIALIZE(ns, MyEnum, A, B, C, D, E, F, G, H) // expands to some serialization code

It would reduce duplication and errors if magic_enum could support extracting enum values in a preprocessor context

// pseudo code
#define MAGIC_ENUM_VALUES(FULLY_QUALIFIED_ENUM_NAME) magic_enum::enum_values<FULLY_QUALIFIED_ENUM_NAME>[0], ...

which would then allow the user to do something like the following

SERIALIZE(ns, MyEnum, MAGIC_ENUM_VALUES(ns##MyEnum))

or even simpler

// Defined once and reused
#define SERIALIZE_ENUM(NAMESPACE, ENUM) SERIALIZE(NAMESPACE, ENUM, MAGIC_ENUM_VALUES(NAMESPACE##ENUM))

// Called for each enum
SERIALIZE_ENUM(ns, MyEnum)

[unterumarmung]

It is a nice idea, but I do not think it's possible.
magic_enum extract the info about enums using metaprogramming and AFAIK there is no way to propagate this information to the preprocessor.
Also, if there would be a way to parse enums at preprocessor-time, I'm sure someone would have already implemented it.