NAME

    Devel::StackTrace - An object representing a stack trace

VERSION

    version 2.01

SYNOPSIS

      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";
      }

DESCRIPTION

    The Devel::StackTrace module contains two classes, C,Devel::StackTrace>
    and Devel::StackTrace::Frame. These objects encapsulate the information
    that can retrieved via Perl's 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.

'TOP' AND 'BOTTOM' OF THE STACK

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

METHODS

    This class provide the following 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 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.

      * filter_frames_early => $boolean

      If this parameter is true, frame_filter will be called as soon as the
      stacktrace is created, and before refs are stringified (if
      unsafe_ref_capture is not set), rather than being filtered lazily
      when Devel::StackTrace::Frame objects are first needed.

      This is useful if you want to filter based on the frame's arguments
      and want to be able to examine object properties, for example.

      * 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.

      * skip_frames => $integer

      This will cause this number of stack frames to be excluded from top
      of the stack trace. This prevents the frames from being captured at
      all, and applies before the frame_filter, ignore_package, or
      ignore_class options, even with filter_frames_early.

      * unsafe_ref_capture => $boolean

      If this parameter is true, then Devel::StackTrace will store
      references internally when generating stacktrace frames.

      This option is very dangerous, and should never be used with
      exception objects. Using this option will keep any objects or
      references alive past their normal lifetime, until the stack trace
      object goes out of scope. It can keep objects alive even after their
      DESTROY sub is called, resulting it it being called multiple times on
      the same object.

      If not set, Devel::StackTrace replaces any references with their
      stringified representation.

      * no_args => $boolean

      If this parameter is true, then Devel::StackTrace will not store
      caller arguments in stack trace frames at all.

      * 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 truncates each
      subroutine 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 on the stack, going
    down. If this method 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 $trace->next_frame() or
    $trace->prev_frame() will work properly.

 $trace->prev_frame()

    Returns the next Devel::StackTrace::Frame object on the stack, going
    up. If this method 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 the next call to $trace->next_frame() or
    $trace->prev_frame() will work properly.

 $trace->reset_pointer

    Resets the pointer so that the next call to $trace->next_frame() or
    $trace->prev_frame() will start at the top or bottom of the stack, as
    appropriate.

 $trace->frames()

    When this method is called with no arguments, it returns a list of
    Devel::StackTrace::Frame objects. They are returned in order from top
    (most recent) to bottom.

    This method can also be used to set the object's frames if you pass it
    a list of Devel::StackTrace::Frame objects.

    This is useful if you want to filter the list of frames in ways that
    are more complex than can be handled by the $trace->filter_frames()
    method:

      $stacktrace->frames( my_filter( $stacktrace->frames() ) );

 $trace->frame($index)

    Given an index, this method returns the relevant frame, or undef if
    there is no 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(\%p)

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

    The optional \%p parameter only has one option. The max_arg_length
    parameter truncates each subroutine argument's string representation if
    it is longer than this number of characters.

SUPPORT

    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.

AUTHOR

    Dave Rolsky <autarch@urth.org>

CONTRIBUTORS

      * Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>

      * David Cantrell <david@cantrell.org.uk>

      * Graham Knop <haarg@haarg.org>

      * Mark Fowler <mark@twoshortplanks.com>

      * Ricardo Signes <rjbs@cpan.org>

COPYRIGHT AND LICENSE

    This software is Copyright (c) 2000 - 2016 by David Rolsky.

    This is free software, licensed under:

      The Artistic License 2.0 (GPL Compatible)

