Devel::StackTrace(3pm) - phpMan

Devel::StackTrace(3pm) User Contributed Perl Documentation Devel::StackTrace(3pm)

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:

o 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.

o 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.

o ignore_package => $package_name OR \@package_names

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

o 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.

o 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".

o 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.

o no_args => $boolean

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

o 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.

o 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.

o 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.

o 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
o Dagfinn Ilmari Mannsaker <ilmari AT ilmari.org>

o David Cantrell <david AT cantrell.uk>

o Graham Knop <haarg AT haarg.org>

o Ivan Bessarabov <ivan AT bessarabov.ru>

o Mark Fowler <mark AT twoshortplanks.com>

o Pali <pali AT cpan.org>

o Ricardo Signes <rjbs AT cpan.org>

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.

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