SelfLoader chokes on closed STDIN

saintmike has asked for the wisdom of the Perl Monks concerning the following question:

There's a handy module called SelfLoader in the perl core, which lets you hide functions in the DATA section and load them on demand:

#!/usr/bin/perl
#sloader
use SelfLoader;
foobar();

__DATA__
sub foobar {
    print "foobar!\n";
}
[download]

Alas, there seems to be a bug with it. If you call the script above from another script via exec and close STDIN, as in

#!/usr/bin/perl
#sloader-exec
close(STDIN);
exec "./sloader";
[download]

it fails:

main doesn't contain an __DATA__ token at ./sloader line 5

Anyone seen this before?

Comment on SelfLoader chokes on closed STDIN Select or Download Code

Replies are listed 'Best First'.
Re: SelfLoader chokes on closed STDIN by liverpole (Monsignor) on Nov 07, 2006 at 00:38 UTC
Hi saintmike, It works for me, on Windows XP, using ActiveState Perl 5.8.8. What O/S and version of Perl are you using? s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/	[reply]
Re^2: SelfLoader chokes on closed STDIN by saintmike (Vicar) on Nov 07, 2006 at 00:41 UTC
perl-5.8.8 on Linux.	[reply]
Re^3: SelfLoader chokes on closed STDIN by liverpole (Monsignor) on Nov 07, 2006 at 00:47 UTC
I'll try this out on a Linux system in a bit, but I've got to ask: Is there a good reason you need to close <STDIN>? Update: For the record -- this worked fine on Linux (RH9), but the version of Perl there is 5.8.6. s''(q.S:$/9=(T1';s;(..)(..);$..=substr+crypt($1,$2),2,3;eg;print$..$/	[reply]
Re^4: SelfLoader chokes on closed STDIN by saintmike (Vicar) on Nov 07, 2006 at 06:20 UTC
Re: SelfLoader chokes on closed STDIN by Tanktalus (Canon) on Nov 07, 2006 at 20:42 UTC
Ugh. It's a bug in SelfLoader. Look for the line that says: `croak("$callpack doesn't contain an __DATA__ token") unless fileno($fh);` [download] It should say: `croak("$callpack doesn't contain an __DATA__ token") unless defined fileno($fh);` [download] Notice the "defined" test? In your system (and mine as well), when you close stdin (fileno 0), the C library reuses that file handle for the next usage - which is reading $0, which goes to main::DATA. So the file number here is 0, which is false, and it croaks. What the author should have* said is "check if there is a file number" - not that it's non-zero. (According to fileno, it returns undef if it's not open.) I suggest opening a bug against it and pointing to this thread. And then you can patch your own if you feel lucky ;-)	[reply] [d/l] [select]
Re^2: SelfLoader chokes on closed STDIN by saintmike (Vicar) on Nov 08, 2006 at 17:27 UTC
Funny, I came to the same conclusion yesterday and got it fixed :).	[reply]