> Because any error but EAGAIN/EINTR is failure. As you convinced
Yep. I thought about this as well.
If you used read with a byte count of 0 / 1, and it returned -1 to
the program with errno set to ENOTCONN, you cannot be confident whether
it is trying to complete a 3 way handshake or the connection failed.
> yourself there is no good way to detect connection completion,
> so in fact writing correct program is next to impossible.
I am a bit jaded about non-blocking connects on Unix, because is even
more non-portable than I ever imagined.
> Actually, never in my life I have seen a pattern of program
> with waits for EISCONN after EINTR on connect() (but lots of them
> fail when not seeing 0), so I have no idea why they work under these OSes.
> Apparently, they fail randomly.
On Solaris / Digital UNIX the 3 way handshake completes asynchronously
on EINTR. Checking for a EISCONN is one non-perfect solution to check
for a successful connection establishment.
So, in the near future, we can expect Linux to not return 0 for
non-blocking connects (i.e. the change you mentioned)?