phpMan > perldoc > Devel::StackTrace

NAME
    Devel::StackTrace - An object representing a stack trace

VERSION
    version 2.04

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, "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.

    If all the frames in a trace are skipped then this just returns the "message" passed to the
    constructor or the string "Trace begun".

  $trace->message
    Returns the message passed to the constructor. If this wasn't passed then this method returns
    "undef".

SUPPORT
    Bugs may be submitted at <https://github.com/houseabsolute/Devel-StackTrace/issues>.

    I am also usually active on IRC as 'autarch' on "irc://irc.perl.org".

SOURCE
    The source code repository for Devel-StackTrace can be found at
    <https://github.com/houseabsolute/Devel-StackTrace>.

DONATIONS
    If you'd like to thank me for the work I've done on this module, please consider making a
    "donation" to me via PayPal. I spend a lot of free time creating free software, and would
    appreciate any support you'd care to offer.

    Please note that I am not suggesting that you must do this in order for me to continue working
    on this particular software. I will continue to do so, inasmuch as I have in the past, for as
    long as it interests me.

    Similarly, a donation made in this way will probably not make me work on this software much
    more, unless I get so many donations that I can consider working on free software full time
    (let's all have a chuckle at that together).

    To donate, log into PayPal and send money to autarch AT urth.org, or use the button at
    <http://www.urth.org/~autarch/fs-donation.html>.

AUTHOR
    Dave Rolsky <autarch AT urth.org>

CONTRIBUTORS
    *   Dagfinn Ilmari Mannsåker <ilmari AT ilmari.org>

    *   David Cantrell <david AT cantrell.uk>

    *   Graham Knop <haarg AT haarg.org>

    *   Ivan Bessarabov <ivan AT bessarabov.ru>

    *   Mark Fowler <mark AT twoshortplanks.com>

    *   Pali <pali AT cpan.org>

    *   Ricardo Signes <rjbs AT cpan.org>

COPYRIGHT AND LICENSE
    This software is Copyright (c) 2000 - 2019 by David Rolsky.

    This is free software, licensed under:

      The Artistic License 2.0 (GPL Compatible)

    The full text of the license can be found in the LICENSE file included with this distribution.