On 12 Apr 2005 03:46:24 -0700, Gisle Aas <[EMAIL PROTECTED]> wrote:
> [EMAIL PROTECTED] (Ton Hospel) writes:
>
> > In article <[EMAIL PROTECTED]>,
> > Rafael Garcia-Suarez <[EMAIL PROTECTED]> writes:
> > > Ok, select($$$$) now returns undef on error as of change #24223.
> >
> > /me raises the backward compatibility police card
> >
> > For what it's worth, I think this is a bad idea.
>
> I can agree that it is a bad idea unless it can be demonstrated that a
> majority of usages of this function assumed undef on error.
> Fortunately we do have CPAN that can be used to do some statistical
> analysis of its usage. I don't think we should keep this change until
> somebody that care enough do this analysis. I assume this change is
> an experiment by Rafael to figure out how many would scream up about
> such a change. I'm surprised by how few do.
>
> > First of all it basically breaks the error handling in all my
> > select() code where I typically do something like:
> >
> > if (select(..) >= 0) {
> > play a bit with time and handles, i don't really care what the exact
> > number that got returned is
> > } elsif ($! == EINTR) {
> > redo some loop;
> > } else {
> > die "Unexpectedd select failure: $!"
> > }
> >
> > So now I'll get pointless undef warnings in the failure case and will
> > never get to the die even if I want it to.
>
> So, how did you figure out this was the right way? Did you read the
> source code for pp_sselect, did you find this by experimentation or
> was this just the obvious mapping to you?
>
> I know I got it wrong because it was "obvious" to me that select
> worked like sysread, which is a function you will almost always use
> together with select.
>
> > So it DOES break existing code.
>
> It sure does.
>
> > And fixing it so it works on *both* versions of perl gets messy too.
>
> I don't know anything better than:
>
> my $nfound = select(...);
for backward compatibility you'd need the opposite
$nfound //= -1;
err ... (ok, bad pun)
defined $nfound or $nfound = -1;
otherwise you'd get an undef warning on this:
> $nfound = undef if $nfound == -1;
> if (defined $nfound) {
> # play a bit with time and handles
> }
> else {
> # failed; check $!
> }
>
> or make a wrapper for select that does this.
>
> > Also notice that there are other calls in perl that do the -1 on failure,
> > see tell(), waitpid(), wait(), syscall(). So it isn't as if it happens
> > nowhere else in perl.
>
> Seems to kill the consistency with sysread argument. There is no way
> we can get consistency between the various builtin functions anyway so
> why try.
--
H.Merijn Brand Amsterdam Perl Mongers (http://amsterdam.pm.org/)
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AIX 4.3 & 5.2, SuSE 9.1 & 9.2, and Cygwin. http://www.cmve.net/~merijn
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