Re: Review of gnio, round 1

[Dan Winship <danw gnome org>]

Alexander Larsson wrote:
> On Mon, 2009-04-27 at 13:22 -0400, Dan Winship wrote:
>>> g_socket_finalize closes socket even if g_socket_close() is already
>>> closed, need to add an is_closed variable. We should also check this in
>>> all operations so that we don't accidentally call stuff on an fd that
>>> may have been reused by now.
>> libsoup's solution here is to implement "close" as
>> shutdown(fd,SHUT_RDWR), and only actually call close(fd) at finalization
>> time.
> 
> Whats the advantage here over close() and then setting some is_closed
> bit?

Well, you don't need an is_closed bit, and you don't need to add a
special check to every op. You just try to recv() or send() or whatever,
and get back ENOTCONN (or whatever it is), and handle that normally just
like if it had been the remote end that closed the connection.

In libsoup it's also important because it's thread-safe/non-racy. That
may not be a relevant criterion for GSocket, although the source
returned by g_socket_create_source() could create similar problems; you
need to be certain that any such sources are destroyed before you call
g_socket_close(), or else they could trigger falsely if the fd gets
reused. Delaying close() until finalization makes that easy because then
you can just have the source hold a ref on the socket to ensure that the
fd doesn't get closed.

-- Dan