Re: MV Debug Statements

[Joe Hourcle <oneiros@dcr.net>]

******    message to minivend-users from Joe Hourcle <oneiros@dcr.net>     ******



On Thu, 25 Feb 1999, Barry Treahy wrote:

> ******    message to minivend-users from Barry Treahy <treahy@mmaz.com>     ******
> 
> Mike, I'm not a Perl expert and need a direct answer.  I've had numerous
> postings about problems with MV, probably my technique but still no
> help, and when I enable debugging, different parts of MV begin to
> mis-behave.
> 
> With debugging enabled, there are a lot of "Use of uninitialized value
> at" errors, many in GDBM and other modules and my question is,
> 
> does Perl continue an execution stream even if an error occurs?  I have
> pages that work without debugging, but when enabled, they stop saving
> data, specifically with userdb.  I need to know if I'm creating more
> work trying to use the debug data than the aid it is providing me...


'Use of uninitialized value' normally means that a variable was called,
and was considered undef (roughly, NULL)

normally, programs will run with those errors messages, however, there is
a possiblility that some things will break:

eg.

	printf OUTPUT "%s will give an error\n",$blah;

will give an error, if $blah has not been defined.  Your sometimes get it
in arrays, when array is smaller than you thought.


eg.
	($id,$descrip,$qty,$crap,$etc) = @array;

if @array is smaller than 5 items, $etc is undef, and will give those
errors each time it's called in some context that needs it to have a
value.

Sometimes, depending on the chances of your data being incomplete, it's
good to do something like:

	($id,$descrip,$qty,$crap,$etc) = @array;
	$descrip = '' if (!defined($descrip));
	$qty     = '' if (!defined($qty));
	$crap    = '' if (!defined($crap));
	$etc     = '' if (!defined($etc));

-----
Joe Hourcle
Digital Crescent, Inc.

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