Learned Monks,

I am trying to use Devel::DProf on some code that uses Safe compartments. I've found that some subroutine names (in "&" lines) in the resulting tmon.out file are corrupted with nonprintable characters. Sometimes the corrupted names contain newlines, which is a problem for dprofpp. I'm using Perl 5.8.8 on FreeBSD 5.4 (compiled from a port). Here's a test program that triggers the problem:

#!/usr/bin/perl

use strict;
use warnings;
use Safe;

my $safe = new Safe;
$safe->reval(q|
sub fibonacci {
        my $index = shift;
        return 0 if $index == 0;
        return 1 if $index == 1;
        return fibonacci( $index - 1 ) + fibonacci( $index - 2 );
}
|);
print "F($ARGV[0]) is ", $safe->reval(qq|fibonacci($ARGV[0])|), "\n";

[download]

When run with "perl -d:DProf", the resulting tmon.out file contains the following odd subroutine lines:

& 2e main  L<13><08>N
& 30 main p<FF><06><08>ON__
& 31 main  L<13><08>N
& 32 main p<FF><06><08>ON__

[download]

(I've replaced the non-printable characters with their hex equivalents.) The second one looks like it's supposed to be "__ANON__", only the first four bytes have been overwritten. Some kind of memory corruption? Multiple runs result in roughly the same output -- the timing it different, but names and sequence of subroutines is the same.

When I run "dprofpp -T", it shows me that the odd subroutines are called by Safe::reval:

Safe::reval
   Safe::lexless_anon_sub
      main::L<13><08>N
         strict::unimport
   Opcode::_safe_call_sv
      main::p<FF><06><08>ON__
Safe::reval
   Safe::lexless_anon_sub
      main::L<13><08>N
         strict::unimport
   Opcode::_safe_call_sv
      main::p<FF><06><08>ON__
         main::fibonacci
            main::fibonacci
               (... and so on)

[download]

This code, however, doesn't produce any corruption:

#!/usr/bin/perl

use strict;
use warnings;

eval(q|
sub fibonacci {
        my $index = shift;
        return 0 if $index == 0;
        return 1 if $index == 1;
        return fibonacci( $index - 1 ) + fibonacci( $index - 2 );
}
|);
print "F($ARGV[0]) is ", eval(qq|fibonacci($ARGV[0])|), "\n";

[download]

My real mod_perl codebase, which makes extensive use of Safe, yields such gems as:

& 471 main <10><98>
id

[download]

What I've come up with so far is a cleaning script that escapes nonprintable bytes and inappropriate newlines:

while (<>) { print; last if /^PART2/ }
while (<>) {
        s/([\x00-\x09\x0b-\x15\x7f-\xff])/"<".sprintf("%X",ord($1)).">
+"/eg;
        /^[@&+\-\/*]/ or $prev =~ s/\n$/<10>/;
        print $prev;
        $prev = $_;
}
print $prev;

[download]

So dprofpp can handle the output, but I have no idea if I'm getting useful profile data. In my real codebase (a large mod_perl app, profiled with Apache::DProf under "httpd -X"), several consecutive requests will result in different garbage values, or no corruption:

Request 1:

WeBWorK::PG::Translator::translate
   Safe::reval
      main::<10><98>
         strict::unimport
      main::<88>'<AA><08>ON__
         main::DOCUMENT

[download]

Request 2:

WeBWorK::PG::Translator::translate
   Safe::reval
      main::<08><83>G<0A>N
         strict::unimport
      main::<F8><CE><99><08>ON__
         main::DOCUMENT

[download]

Request with no corruption:

WeBWorK::PG::Translator::translate
   Safe::reval
      main::BEGIN
         strict::unimport
      main::__ANON__
         main::DOCUMENT

[download]

My question is: what gives? I'm hoping that others have seen this before and can suggest a solution, or at least tell me "Stop trying, Safe and DProf are not compatible". Or maybe it's not a problem -- the corruption seems to be localized, and the routines in question don't run for very long. (For example, main::<E4><F2><99><08>ON__ runs for 0.049s.)

In reply to DProf + Safe = corrupted tmon.out by smammy

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