While I understand how my problem happens, it just caught me again
(letting me debug another two hours), and so I wanted to ask why this
peculiar behaviour is really necessary.
But straight to the point. If I have a module like this:
=============================================================================
package othermodule;
my $global = 5;
sub set_global {
$global = shift;
}
=============================================================================
And use this from another module:
=============================================================================
othermodule::set_global 7;
=============================================================================
Then, to my surprise, _sometimes_ the $global will be set, and sometimes not.
The reason for this seems to be that othermodule is parsed twice: Once
during configuration parsing and once later. The first time it is parsed,
$global is created and bound to ste_global. Other modules that call the
function get a reference to it cimpiled in.
Then, when the file is parsed again, _another_ instance of $global gets
created, and another instance of set_global is compiled. Now there are two
versions of set_global, two versions of $global, and which one gets called
very much depends on random factors.
To my pity, _some_ global (non-lexical) variables also get cleared, but
not in all packages.
Now, since this is really hard to debug (the order of function declaration
within the same file and wether the funciton is exported or not, and
wether there are other callers outside the file etc...
To remedy this, many of my modules (the bad point is that even modules I have
no control over suffer from this problem) start with something like this:
=============================================================================
if (!defined $PApp::Apache::compiled) { eval do { local $/; <DATA> };
die $@ if $@ } 1;
__DATA__
#line 6 "(PApp::Apache source)"
=============================================================================
This mostly remedies the situation. The only "side effects" that I found
so far is that my httpds reuqire much _less_ memory and run _much_ more
stable (mod_perl really is very unstable for large applications). Apart
from expected semantics of global lexical variables.
So.... my very own problem is solvable (either by using package variables
or that ugly but working trick above). Third-party modules (e.g. from
CPAN) however, still suffer from this problem, and due to my dumbness I
fall into that trap again and again.
And so my question is: why does this behaviour exist, and why is it
necessary (the documents I saw so far only told me that this "has
something to do with apache's configuration file parsing", which doesn't
explain much, especially as it does seem unnecessary).
Thanks a lot for any feedback ;)
--
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---==---(_)__ __ ____ __ Marc Lehmann +--
--==---/ / _ \/ // /\ \/ / [EMAIL PROTECTED] |e|
-=====/_/_//_/\_,_/ /_/\_\ XX11-RIPE --+
The choice of a GNU generation |
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