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Enbugger - Enables the debugger at runtime.


    my $ok = eval { ...; 1 };
    if ( not $ok ) {
        # Oops! there was an error! Enable the debugger now!
        require Enbugger;


Allows the use of the debugger at runtime regardless of whether your process was started with debugging. This is useful if you would like to add hooks so the debugger is loaded on some kind of event or UNIX signal or if for some reason you're having difficulty running your program with debugging turned on at compile time.


To install this module, run the following commands:

    perl Makefile.PL
    make test
    make install


Loading the debugger

Loading the debugger at process start time works just like normal.

  perl -d ...

You can also load the debugger at runtime:

  use Enbugger;

You can load a specific debugger:

  use Enbugger;
  Enbugger->load_debugger( 'perl5db' );

You can specific a default debugger:

  $Enbugger::DefaultDebugger = 'perl5db';


  use Enbugger 'perl5db';

Unloading the debugger

You wish. There is no implemented way to unload the debugger. Here's how you'd do it if you wanted to implement this feature.


Set the various C pointers set by Perl_init_debugger to NULL


Clear the DB:: package. Beware of the DB and sub functions. If you ever load another debugger again you'll need to ensure you have at least stub functions left or you could suffer a fatal, deadly death.


Change all dbstate B::COP nodes back to be nextstate ops.



Call the public class method Enbugger->stop. At a minimum, it will just request that your current debugger stop execution.

If needed, it'll go as far as loading a debugger.

An example

  if ( ... ) {
      # an unlikely occurance I'd like to manually inspect if or when
      # it happens.

On %SIG events

If you load the Enbugger::OnError module, you can use unhandled exceptions or UNIX signals as break points. In addition, loading the debugger is deferred until your signal or exception is triggered.

I like using this with both die() and SIGUSR1 handled enough that both are the default for handling.

  use Enbugger::OnError;
  use Enbugger::OnError qw( __DIE__ USR1 ); # equivalent

A program using the above line will trigger a break point whenever an unhandled die() occurs or whenever the USR1 signal is received. To use other signals, just specify them at the use().

  use Enbugger::OnError qw( USR1 USR2 INT HUP );

An example

Here's a quick example of breaking into a long running program to see what it's doing.

At one terminal:

  bash$ perl -MEnbugger::OnError -e 'while(1) {}'

At a separate terminal:

  bash$ ps x | grep perl
  12850 pts/1    R      0:01 perl -MEnbugger::OnError -le while(1){}
  12852 pts/1    R+     0:00 grep perl
  bash$ kill -USR1 12850

Back at the original perl program:

  Loading DB routines from version 1.3
  Editor support available.

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

  Received signal USR1 at -e line 1
          eval {...} called at -e line 1

    DB<1> T
  $ = Enbugger::OnError::ExceptionHandler('USR1') called from -e line 1
  $ = eval {...} called from -e line 1
    DB<1> q

From gdb

You can attach to a running process and inject a perl debugger even when you didn't originally plan for this. This works very much like perl's unsafe signals so there's a reasonable chance that your process could go pear shaped after doing this.

Have something to connect to:

  bash$ perl -e 'while(1) {}' &
  [1] 16061
  bash$ ps x | grep perl
  16061 s002  R      0:16.91 perl -e while(1) {}

Attach with GDB (

  bash$ gdb -p 16061
  GNU gdb 6.3.50-20050815 (Apple version gdb-768) (Tue Oct  2 04:07:49 UTC 2007)
  Copyright 2004 Free Software Foundation, Inc.
  GDB is free software, covered by the GNU General Public License, and you are
  welcome to change it and/or distribute copies of it under certain conditions.
  Type "show copying" to see the conditions.
  There is absolutely no warranty for GDB.  Type "show warranty" for details.
  This GDB was configured as "i386-apple-darwin".
  /Users/jbenjore/16061: No such file or directory.
  Attaching to process 16061.
  Reading symbols for shared libraries . done
  Reading symbols for shared libraries ...... done
  0x001be987 in Perl_pp_unstack ()

Detect whether you are attaching to a threaded or unthreaded perl. When this function returns zero, omit it from the Perl_eval_pv() call:

  (gdb) call (void*)Perl_get_context()
  $1 = (void *) 0x800000


  (gdb) call (void*)Perl_get_context()
  $1 = (void *) 0x0

Inject a debugger into a threaded build. Optionally, send a debugger to someplace like a remote terminal. Read for more options.

  (gdb) call (void*)Perl_eval_pv((void*)Perl_get_context(),"eval{require Enbugger;warn q(stopping);$ENV{PERLDB_OPTS}='RemotePort=localhost:4000';Enbugger->stop;};print STDERR $@",0)

OR inject a debugger into an unthreaded build:

  (gdb) call (void*)Perl_eval_pv("eval{require Enbugger;warn q(stopping);$ENV{PERLDB_OPTS}='RemotePort=localhost:4000';Enbugger->stop;};print STDERR $@",0)

Receive a perl debugger.

  Reading symbols for shared libraries . done
  Reading symbols for shared libraries . done
  Reading symbols for shared libraries . done
  Reading symbols for shared libraries . done
  Reading symbols for shared libraries . done

  Loading DB routines from version 1.32
  Editor support available.

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

  $2 = (void *) 0x85c000
  main::((eval 16)[-e:1]:1):eval{warn q(stopping);require Enbugger;Enbugger->stop};print STDERR $@
    DB<1> p "Hi, I am in perl verson $] now"
  Hi, I am in perl verson 5.010000 now
  DB<2> T
    $ = eval 'eval{warn q(stopping);require Enbugger;Enbugger->stop};print STDERR $@' called from -e line 1

Return control back to gdb:

  DB<3> c

Return control back to the program:

  (gdb) detach
  Detaching from process 16314 thread 0x10b.
  (gdb) q


Enbugger has a public API where you as the user can trigger the debugger from your code or affect which debugger is loaded.


Stops execution and signals your debugger. Loads a debugger with CLASS->load_debugger if one hasn't been loaded yet.

CLASS->load_debugger( DEBUGGER )

Loads your requested debugger. Defaults to using $Enbugger::DefaultDebugger if you don't specify a debugger.

If a debugger has already been loaded, either returns silently if the current debugger is what you requested or throws an exception if you requested a different debugger.


The default debugger. This is perl5db unless you change it.

CLASS->write( TEXT )

Writes some thing to the console or wherever is appropriate for your current debugger.


Returns the class name for the currently loaded debugger class.

If no debugger has been loaded yet, this contrives to load the default debugger.


Enbugger supports registering debuggers. Any debugger intended to be used must be registered first. The default, proper behavior is to register all possible debuggers.

Registered debuggers

The following is a list of all default, registered debuggers. So far only the debugger has received any testing.


This is the default perl debugger. See also Enbugger::perl5db and


This is the Devel::Trepan debugger. See also Devel::Trepan or

Registering your own debugger

While I've attempted to register some debuggers by by default, you may need to write your own Enbugger::$foo class to register your own debugger. Currently there is no way to use an unknown debugger without first writing an Enbugger subclass.

CLASS->register_debugger( DEBUGGER )

Register a debugger with Enbugger.

Required methods

You must implement the following methods.


Your debugger must implement a _stop method. This method will be called by the Enbugger->stop method. When this method is called, you should stop the current process and invoke your debugger.


Your debugger must implement a load_debugger method. It will be called when your debugger should be loaded. Your method is responsible for loading the debugger.

CLASS->_write( TEXT )

Your debugger must implement a _write method. This method should accept text to log to the console or whatever is appropriate.



Loads the source code for the program.

CLASS->load_file( FILE )

Loads the source code for a specific file.


Sets all available breakpoints to be either breakable or not. This avoids making any part of the Enbugger:: or DB:: packages a part of something that's visible to the debugger.

instrument_op( B::*OP )

A function that modifies B::COP objects.


The followings methods exist but I'm not sure whether they'll continue to exist in their current form so they're private for now.



A C compiler.


After installing, you can find documentation for this module with the perldoc command.

    perldoc Enbugger::Restarts

You can also look for information at:

RT, CPAN's request tracker
AnnoCPAN, Annotated CPAN documentation
CPAN Ratings
Search CPAN


Joshua ben Jore ><


Brock Wilcox (awwaiid)
R. Bernstein (rocky)
Erkan Yilmaz
Robert Messer at IntelliSurvey for sponsoring breakpoints


Copyright (C) 2007, 2008, 2009, Inc. with primary development by Joshua ben Jore.

This program is distributed WITHOUT ANY WARRANTY, including but not limited to the implied warranties of merchantability or fitness for a particular purpose.

The program is free software. You may distribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation (either version 2 or any later version) and the Perl Artistic License as published by O’Reilly Media, Inc. Please open the files named gpl-2.0.txt and Artistic for a copy of these licenses.

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