[asio-users] asio::error::basic_errors::not_supported is missing

[Vinícius d. S. O. <vin...@gm...>]

On POSIX systems, asio::error::basic_errors will be just an alias for
values that ASIO uses from std::system_category().

One of these is operation_not_supported (which is EOPNOTSUPP). However
EOPNOTSUPP may alias ENOTSUP on some systems. For Linux and FreeBSD,
these errno values are the same. For OpenBSD, macOS, and a few others
they differ.

When a composed operation throws ENOTSUP, the caller might
accidentally catch EOPNOTSUPP on Linux or FreeBSD. There isn't really
any good answer here. However I think Boost.Asio should just define
asio::error::basic_errors::not_supported and document that
not_supported and operation_not_supported might be aliases on some
systems (they are on Linux and FreeBSD). That's what C++11 already
does in a way by including both definitions so Boost.Asio could just
follow along as well.


-- 
Vinícius dos Santos Oliveira
https://vinipsmaker.github.io/