enums in C++

[Phil Edwards]

Ulrich Drepper <drepper@redhat.com>:
> Nathan Sidwell <nathan@codesourcery.com> writes:
>
> > Remember, stuff inside `extern "C" { ... }' must still be valid
> > C++. Also remember, the set of overloaded functions named `foo' must
> > have distinct parameters, only one of the set can have C linkage.
>
> Yes, it must be valid C++ but the rules must be relaxed.  It must be
> possible to call the functions the way you can do this in C.

The code /inside/ an extern-C block should have certain rules relaxed,
definitely.  But I respectfully disagree that the /calling/ code should
have its language semantics silently changed by the linking convention of
the code being called.  That way lies silent disaster.


> It simply does not help insisting that they write C++.  You have to
> use C libraryies at some point and then you have to use their
> interface.  If the interface is defined using enum of bit values then
> people can reasonably expect it to work just as in C.

Given your example, I would expect

    foo (static_cast<ex_enum>(A | B))

to work exactly as it works in C.  Perhaps I'm missing something -- what
do you find objectionable about that code?


> This is apparently how other C++ work.  Otherwise this code wouldn't
> be in such wide use.  At least relax the rules when using
> -fpermissive.

Aye, other C++ implementations get this wrong...  I could see relaxing
the rules when using -fpermissive, though.


Phil