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

Om mani padme hum ...

I'm debugging a program and am seeing this message: 

panic: malloc at /usr/lib/perl5/5.8.6/Carp/Heavy.pm line 61.
Debugged program terminated.

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The code at line 61 of Carp::Heavy is: 

  $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;

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and it is preceded by a comment: 

  # The following handling of "control chars" is direct from
  # the original code - I think it is broken on Unicode though.
  # Suggestions?

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The whole module of course starts with the legendary words: 

  heavy machinery, no user serviceable parts inside

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I've searched around a bit without finding anything about my problem. Neither my code nor data does anything with Unicode; it's all ASCII AFAIK. I'm running perl v5.8.6. Can anybody suggest an approach to this problem?

Thanks, Dave

PS I see that the latest version of Carp::Heavy on CPAN has slightly different code that mentions utf8, but it still has the same comment!

Replies are listed 'Best First'.
Re: Carp::Heavy panic: malloc Unicode?
by Steve_p (Priest) on Feb 07, 2007 at 20:25 UTC

    That bit of code is broken and should be available in a newer version of Perl. The patch below resolved the problem.

    Change 25363 by rgs@bloom on 2005/09/07 11:09:10

    The formatting function of Carp::Heavy has problem with utf8 strin
+gs.
    Work around it.

Affected files ...

... //depot/perl/lib/Carp/Heavy.pm#24 edit

Differences ...

==== //depot/perl/lib/Carp/Heavy.pm#24 (text) ====

@@ -116,9 +116,10 @@
   $arg = "'$arg'" unless $arg =~ /^-?[\d.]+\z/;
 
   # The following handling of "control chars" is direct from
-  # the original code - I think it is broken on Unicode though.
+  # the original code - it is broken on Unicode though.
   # Suggestions?
-  $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1))/eg;
+  utf8::is_utf8($arg)
+    or $arg =~ s/([[:cntrl:]]|[[:^ascii:]])/sprintf("\\x{%x}",ord($1)
+)/eg;
   return $arg;
 }

    [download]

    Test your modules with bleadperl!

      rsync -avz rsync://public.activestate.com/perl-current/ .
  ./Configure -des -Dusedevel -Dprefix=/path/to/test/perl
  make test
  make install

    Now, please test you modules! If you have test failures that don't happen with Perl 5.8.8, send a simplified test case to 

    perlbug at perl.org
[reply]
[d/l]
      Wow. That piece of enlightenment gives me hope that someday I might be able to use the perl debugger with unicode data... I've had repeated failures when using "perl -d" on scripts that involve regex operations on utf8 strings, in 5.8.6 on macosx and 5.8.7 on freebsd. A script would run okay by itself (except for bugs), but running it with "perl -d" leads to various reports of "out of memory" at the first unicode-heavy regex. So, I'm guessing the debugger contains something similar to the logic you've cited in Carp::Heavy. (But curiously, I can run a one-liner applying that regex to a utf8 string on my mac without difficulty. I'm confused.)

      Anyway, I can't say that I approve of the approach taken in that patch. All it's doing is: if the string has the utf8 flag on, avoid trying to make any non-visible or non-ascii characters "displayable" by converting them to hex notation.

      Rather than just give up completely on utf8 strings, wouldn't it be better to use a different approach? e.g.: 

      $arg = join "", 
       map {
             ($_ lt ' ' or $_ gt '~') ? sprintf("\\x{%x}",ord) : $_ 
           } split //, $arg;

      [download]
      I'm not sure, but I think that should avoid the malloc explosion caused by using [[:cntrl:]]|[[:^ascii:]] on a utf8 string.
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[d/l]
[select]
Re: Carp::Heavy panic: malloc Unicode?
by shmem (Chancellor) on Feb 07, 2007 at 16:29 UTC
    Perl croaks in Perl_malloc (in malloc.c). perldiag states:
    panic: malloc
    (P) Something requested a negative number of bytes of malloc.

    It would be interesting to know what's in $arg just before the crash. Maybe insert a print statement at line 60 into Carp::Heavy?

    --shmem 

    _($_=" "x(1<<5)."?\n".q·/)Oo.  G°\        /
                              /\_¯/(q    /
----------------------------  \__(m.====·.(_("always off the crowd"))."·
");sub _{s./.($e="'Itrs `mnsgdq Gdbj O`qkdq")=~y/"-y/#-z/;$e.e && print}
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[d/l]
Re: Carp::Heavy panic: malloc Unicode?
by jmcnamara (Monsignor) on Feb 07, 2007 at 13:08 UTC

    I can't say if it is the case here but any time that I've encountered Carp::Heavy errors/warnings it has been a problem not with Carp::Heavy but with the parent program consuming too many system resources such as memory or open file handles.

    Update: Looks like it was a Carp::Heavy problem this time. See Steve_p's answer below.

    --
    John.

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