Why does entt still use std::allocator<void>?

[alakanu]

Some files like src/entt/signal/fwd.hpp make use of std::allocator<void> which was deprecated in C++17 and removed in C++20. Depending on the compiler being used, they can be more or less vocal about this warning, which could result in spam in the output. Therefore, I was wondering if there is a reason why entt still uses std::allocator<void> as a default type parameter in latest releases. Does anybody know? If not, does anybody know what is the purpose of declaring a default type parameter for forward declarations of templates like basic_dispatcher? Does it reduce the compilation time by giving hints to the compiler somehow?

[skypjack]

Not sure why you mention std::allocator in the comment. It's clearly still with us in C++20. I assume you meant std::allocator<void>, right?
In this case and as far as I remember, also std::allocator<void> is not deprecated nor removed. The explicit specialization is. Did something change in the meantime?

[alakanu]

I hadn't escaped the < > and as a result <void> was removed altogether :( . I've updated the original post. At this point I think some vendors have not caught the nuance of using vs having an explicit specialisation and added warnings when using it. For example afaik msvc has it deprecated and they added a special macro to suppress the warning _SILENCE_CXX17_ALLOCATOR_VOID_DEPRECATION_WARNING.

Anyway, to go back to my question, is there a specific reason why std::allocator<void> is used there? Could it be replaced by std::allocator<char> to achieve the same outcome? I did that and it seemed ok but maybe I am missing something.

[skypjack]

is there a specific reason why std::allocator is used there? Could it be replaced by std::allocator to achieve the same outcome?

char as well as any other type T would be wrong because here we want to express the absence of a specific type. The allocator is there to ::rebind it to the right type. Literally.

[zaucy]

I believe the deprecation warning is a mistake on msvc's part. As skypjack mentioned its only the explicit specialization that's deprecated. Are you using the latest version of msvc?