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8 non-PAUSE users.

Dave Rolsky


Devel::StackTrace - An object representing a stack trace


version 1.25


  use Devel::StackTrace;

  my $trace = Devel::StackTrace->new;

  print $trace->as_string; # like carp

  # from top (most recent) of stack to bottom.
  while (my $frame = $trace->next_frame) {
      print "Has args\n" if $frame->hasargs;

  # from bottom (least recent) of stack to top.
  while (my $frame = $trace->prev_frame) {
      print "Sub: ", $frame->subroutine, "\n";


The Devel::StackTrace module contains two classes, Devel::StackTrace and Devel::StackTrace::Frame. The goal of this object is to encapsulate the information that can found through using the caller() function, as well as providing a simple interface to this data.

The Devel::StackTrace object contains a set of Devel::StackTrace::Frame objects, one for each level of the stack. The frames contain all the data available from caller().

This code was created to support my Exception::Class::Base class (part of Exception::Class) but may be useful in other contexts.


When describing the methods of the trace object, I use the words 'top' and 'bottom'. In this context, the 'top' frame on the stack is the most recent frame and the 'bottom' is the least recent.

Here's an example:

  foo();  # bottom frame is here

  sub foo {

  sub bar {
     Devel::StackTrace->new;  # top frame is here.

Devel::StackTrace METHODS

  • Devel::StackTrace->new(%named_params)

    Returns a new Devel::StackTrace object.

    Takes the following parameters:

    • frame_filter => $sub

      By default, Devel::StackTrace will include all stack frames before the call to its its constructor.

      However, you may want to filter out some frames with more granularity than 'ignore_package' or 'ignore_class' allow.

      You can provide a subroutine which is called with the raw frame data for each frame. This is a hash reference with two keys, "caller", and "args", both of which are array references. The "caller" key is the raw data as returned by Perl's caller() function, and the "args" key are the subroutine arguments found in @DB::args.

      The filter should return true if the frame should be included, or false if it should be skipped.

    • ignore_package => $package_name OR \@package_names

      Any frames where the package is one of these packages will not be on the stack.

    • ignore_class => $package_name OR \@package_names

      Any frames where the package is a subclass of one of these packages (or is the same package) will not be on the stack.

      Devel::StackTrace internally adds itself to the 'ignore_package' parameter, meaning that the Devel::StackTrace package is ALWAYS ignored. However, if you create a subclass of Devel::StackTrace it will not be ignored.

    • no_refs => $boolean

      If this parameter is true, then Devel::StackTrace will not store references internally when generating stacktrace frames. This lets your objects go out of scope.

      Devel::StackTrace replaces any references with their stringified representation.

    • respect_overload => $boolean

      By default, Devel::StackTrace will call overload::AddrRef() to get the underlying string representation of an object, instead of respecting the object's stringification overloading. If you would prefer to see the overloaded representation of objects in stack traces, then set this parameter to true.

    • max_arg_length => $integer

      By default, Devel::StackTrace will display the entire argument for each subroutine call. Setting this parameter causes it to truncate the argument's string representation if it is longer than this number of characters.

    • message => $string

      By default, Devel::StackTrace will use 'Trace begun' as the message for the first stack frame when you call as_string. You can supply an alternative message using this option.

    • indent => $boolean

      If this parameter is true, each stack frame after the first will start with a tab character, just like Carp::confess().

  • $trace->next_frame

    Returns the next Devel::StackTrace::Frame object down on the stack. If it hasn't been called before it returns the first frame. It returns undef when it reaches the bottom of the stack and then resets its pointer so the next call to next_frame or prev_frame will work properly.

  • $trace->prev_frame

    Returns the next Devel::StackTrace::Frame object up on the stack. If it hasn't been called before it returns the last frame. It returns undef when it reaches the top of the stack and then resets its pointer so pointer so the next call to next_frame or prev_frame will work properly.

  • $trace->reset_pointer

    Resets the pointer so that the next call next_frame or prev_frame will start at the top or bottom of the stack, as appropriate.

  • $trace->frames

    Returns a list of Devel::StackTrace::Frame objects. The order they are returned is from top (most recent) to bottom.

  • $trace->frame ($index)

    Given an index, returns the relevant frame or undef if there is not frame at that index. The index is exactly like a Perl array. The first frame is 0 and negative indexes are allowed.

  • $trace->frame_count

    Returns the number of frames in the trace object.

  • $trace->as_string

    Calls as_string on each frame from top to bottom, producing output quite similar to the Carp module's cluck/confess methods.


Please submit bugs to the CPAN RT system at http://rt.cpan.org/NoAuth/ReportBug.html?Queue=Devel%3A%3AStackTrace or via email at bug-devel-stacktrace@rt.cpan.org.


  Dave Rolsky <autarch@urth.org>


This software is Copyright (c) 2010 by Dave Rolsky.

This is free software, licensed under:

  The Artistic License 2.0