Since this is compile-time reflection, can't the compiler generate reflection metadata "on demand" (that is, whenever it is being queried) rather than the user having to explicitly mark classes as reflected, without any loss of efficiency?
This is actually mentioned in the "Implementation hints" section, and yes the compiler should generate meta-data lazily, but the problem is that I would like to be able to traverse the members of a scope (namespace, class, ...). You can imagine what would happen if such operation instantiated for example ALL members of the boost or std namespace.
I see, good point.
There are some ideas on how to solve this in the "Unresolved issues" section but it is rather complicated:
- If we allow everything to be reflected the compile-times would be horrible, even worse if a run-time reflection facility was based on this meta-data so would be the resulting executable size.
- If we allow some sort of "white-listing" (i.e. specify what you want) or "black-listing" (specify what you don't want) it would be inconvenient for some use-cases.
I'm a fan of the "white-list" approach, but I would like to hear your opinions on this issue.
Whitelisting seems appropriate. To make it more convenient, it would be nice to be able to white-list at different granularities - for example, an entire namespace (meaning all its contents), or just particular elements of a namespace. I also like the idea of separating the whitelisting from the definition of the namespace/class. For example, I may *want* to traverse all the elements of namespace std, so I should be able to whitelist it in my code only. Regards, Nate