goto grief

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

Hi,
On win32, build 817 (perl 5.8.8) of ActivePerl my 'perl -V:xxxx' commands have decided to stop working.Here's an example:

D:\>perl -V:useperlio
&Config::AUTOLOAD failed on Config::launcher at E:/Perl817/lib/Config.
+pm line 72.
[download]

I traced the problem back to the AUTOLOAD subroutine in Config.pm. For debugging, I inserted a print() into that sub. It now looks like this:

sub AUTOLOAD {
    my $config_heavy = 'Config_heavy.pl';
    if (defined &ActivePerl::_CONFIG_HEAVY) {
       $config_heavy = ActivePerl::_CONFIG_HEAVY();
    }
    require $config_heavy;
    print "\$Config::AUTOLOAD: $Config::AUTOLOAD\n"; # inserted by syp
+hilis
    goto \&launcher unless $Config::AUTOLOAD =~ /launcher$/;
    die "&Config::AUTOLOAD failed on $Config::AUTOLOAD"; # line 73, wa
+s line 72
}
[download]

(ActivePerl::_CONFIG_HEAVY is not defined.)
Apart from the print(), the AUTOLOAD sub is unchanged.

I noted that Config_heavy.pl's launcher() subroutine gets called if $Config::AUTOLOAD does not match /launcher$/. I also inserted a print() into that subroutine. It now looks like this:

sub launcher {
    print "\n\nrunning launcher()\n\n"; # inserted by syphilis
    undef &AUTOLOAD;
    goto \&$Config::AUTOLOAD;
}
[download]

Again, apart from the print(), that sub is unchanged.

Now when I run the same command, I get:

D:\>perl -V:useperlio
$Config::AUTOLOAD: Config::fetch_string
$Config::AUTOLOAD: Config::launcher
$Config::AUTOLOAD: Config::launcher
&Config::AUTOLOAD failed on Config::launcher at E:/Perl817/lib/Config.
+pm line 73.
[download]

So ... the first time AUTOLOAD gets called, $Config::AUTOLOAD equates to "Config::fetch_string", yet, as you can see from the fact that "running launcher" has not been printed out, Config_heavy.pl's launcher() sub routine has not been run. How can that possibly be ?

I thought, perhaps, there's another launcher() sub/sunction that got found, but a search of my entire perl installation for the string "launcher" did not turn up such a sub/function - except for the one specified in Config_heavy.pl.

On a separate computer (a laptop) I have the very same build of perl. Running a 'diff -u' on the respective Config.pm and Config_heavy.pl files reveals that they are the same on both the laptop and the (broken) desktop. Yet, on the laptop, everything works correctly, and as expected. That is, I get (using the same debug print statements):

D:\>perl -V:useperlio
$Config::AUTOLOAD: Config::fetch_string

running launcher

useperlio='define';
[download]

Further to that, I can reproduce the error on the laptop if I comment out the require() in the AUTOLOAD subroutine. I feel that getting launcher() to run is crucial to getting things working again - but I can't for the life of me see why it doesn't get run, or what further steps I can take to troubleshoot this. It's a tall order to expect someone to be able to solve this for me, on the evidence I've provided - but any thoughts on what I can do to reach an understanding of what's screwed up are definitely appreciated.

Anyone been bitten by anything remotely like this ? It used to be ok ... hard to say exactly when it broke, but it was ok a month or so ago.

Other than that, I'll just have to re-install ... which will either fix the problem or make no difference at all. Either way, I'll be none the wiser.

Cheers,
Rob

Comment on goto grief Select or Download Code

Replies are listed 'Best First'.
Re: goto grief (@INC) by tye (Sage) on Oct 10, 2006 at 12:22 UTC
Perhaps you have a different (extra) Config_heavy.pl that is being found instead of the one that matches the one that works correctly on the other computer? Add `$INC{"Config_heavy.pl"}` to your debug output? - tye	[reply] [d/l]
Re^2: goto grief (@INC) by syphilis (Archbishop) on Oct 10, 2006 at 23:44 UTC
Add $INC{"Config_heavy.pl"} to your debug output Excellent idea - but it shows that the Config_heavy.pl that has been loaded is the one I expected - the one that contains the debug print(). I inserted `$INC{$config_heavy}` rather than `$INC{"Config_heavy.pl"}` just in case $config_heavy had been set to something unexpected. Anyway, here's the output: `D:\>perl -V:useperlio $Config::AUTOLOAD: Config::fetch_string $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl $Config::AUTOLOAD: Config::launcher $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl $Config::AUTOLOAD: Config::launcher $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl &Config::AUTOLOAD failed on Config::launcher at E:/Perl817/lib/Config. +pm line 73.` [download] I also went so far as to insert, immediately after the "require $config_heavy;" in the AUTOLOAD sub the following block of code: `open(RD, "<", $INC{$config_heavy}) or die "Can't open $INC{$config_heavy}: $!"; while(<RD>) {print $_ if $_ =~ /launcher/} close(RD) or die "Can't close $INC{$config_heavy}: $!";` [download] That gives the following output as I expected: D:\>perl -V:useperlio sub launcher { print "\n\nrunning launcher()\n\n"; $Config::AUTOLOAD: Config::fetch_string $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl sub launcher { print "\n\nrunning launcher()\n\n"; $Config::AUTOLOAD: Config::launcher $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl sub launcher { print "\n\nrunning launcher()\n\n"; $Config::AUTOLOAD: Config::launcher $INC{$config_heavy}: E:/Perl817/lib/Config_heavy.pl &Config::AUTOLOAD failed on Config::launcher at E:/Perl817/lib/Config. +pm line 77. [download] I've only just now discovered that if I set `$ENV{ACTIVEPERL_CONFIG_DISABLE}` then the problem goes away. Of course, I don't really want to do that as I need those ActivePerl::Config values, but it does indicate that it might be a good idea to do a 'diff-u' on the respective ActivePerl::Config.pm files. I'll update this post if that leads to a resolution of this issue. Anonymous Monk wondered whether the same behaviour occurs when I try the same thing from a script. Yes, it produces the same output. Cheers, Rob UPDATE: In the end, I've simply re-installed build 817 straight over the top of the exisiting install, made my usual couple of changes to Config.pm and ActivePerl/Config.pm, and everything's working fine. I will never know what caused the problem - all I do know is that it wasn't anything in Config.pm, Config_heavy.pl or ActivePerl/Config.pm, as these files are now exactly the same as the files that got overwritten (minus my debug prints). The "usual couple of changes" I make are to set `$Config{ld}` to 'g++' rather than 'gcc', and to set `$Config{lib_ext}` to '.a' instead of '.lib'. That's so I can use ActivePerl with the MinGW compiler. It's just those 2 values that need to be amended - the rest are taken care of correctly.	[reply] [d/l] [select]
Re: goto grief by Anonymous Monk on Oct 10, 2006 at 12:22 UTC
Is `use Config; print $Config{useperlio};` [download] affected?	[reply] [d/l]