debugger and warn strangeness

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

The following demonstrates a problem I've come across with the use of the Perl debugger and the warn builtin. I have tried to isolate the problem to as little Perl code as possible. Anyone have a clue how I might get more info from Perl on what's going on?

Thanks,

Harry DeLano

hdelano@adelphia.net

[delano@blackbox test]$ cat junk1
digraph "db-a12" {
        size="6,2.75";
        page="8.5,11";
    margin="1";
[delano@blackbox test]$ cat warnproblem.pl
open I , "junk1";
@b = <I>;
close I;
@c[0] = "\tmargin=\"1\";\n";
warn "entering xxx\n";
xxx( @c);
$c[0] = $b[3];
warn "entering xxx\n";
xxx( @c);
exit;
sub xxx {
    warn "hi.\n";
    return;
}
[delano@blackbox test]$ perl -d warnproblem.pl

Loading DB routines from perl5db.pl version 1.19
Editor support available.

Enter h or `h h' for help, or `man perldebug' for more help.

main::(warnproblem.pl:1):    open I , "junk1";
  DB<1> c
entering xxx
hi.
    main::xxx('\x{9}margin="1";\x{a}') called at warnproblem.pl line 6
entering xxx
panic: malloc.
Debugged program terminated.  Use q to quit or R to restart,
  use O inhibit_exit to avoid stopping after program termination,
  h q, h R or h O to get additional info.  
  DB<1> q
[download]

Comment on debugger and warn strangeness Download Code

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Re: debugger and warn strangeness by halley (Prior) on Feb 25, 2004 at 17:35 UTC
I think you want to phrase your first assignment as a scalar, not a slice. That is, change the `@c[0]` to `$c[0]`. `$c[0] = "\tmargin=\"1\";\n";` [download] This really shouldn't have any effect one way or the other on the operation, since you never declare the `@c` array anywhere, but maybe the debugger's getting confused. It's generally safer to `use strict` so that you develop the habit of declaring variables and arrays, rather than letting them auto-vivify magically. The panic happens in the second call to `xxx`, on the second execution of the same warn line. Does this happen without the debugger? Does this happen with other ways of initializing `@b`? What version of Perl, and what operating system? I'm guessing Linux from your prompt. -- `[ e d @ h a l l e y . c c ]`	[reply] [d/l] [select]

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Re: debugger and warn strangeness
by halley (Prior) on Feb 25, 2004 at 17:35 UTC

@c[0]

$c[0]

$c[0] = "\tmargin=\"1\";\n";
[download]

@c

It's generally safer to use strict so that you develop the habit of declaring variables and arrays, rather than letting them auto-vivify magically.

The panic happens in the *second* call to xxx, on the second execution of the same warn line. Does this happen without the debugger? Does this happen with other ways of initializing @b? What version of Perl, and what operating system? I'm guessing Linux from your prompt.

--
[ e d @ h a l l e y . c c ]

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