Devel::StackTrace - An object representing a stack trace
version 2.05
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. These objects encapsulate the information that can retrieved via Perl's caller function, as well as providing a simple interface to this data.
Devel::StackTrace
caller
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.
Devel::StackTrace::Frame
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 { bar(); } sub bar { Devel::StackTrace->new; # top frame is here. }
This class provide the following methods:
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.
@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.
frame_filter
unsafe_ref_capture
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.
ignore_package
ignore_class
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.
DESTROY
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.
overload::AddrRef
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.
as_string
indent => $boolean
If this parameter is true, each stack frame after the first will start with a tab character, just like Carp::confess.
Carp::confess
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.
undef
$trace->next_frame
$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.
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.
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:
$trace->filter_frames
$stacktrace->frames( my_filter( $stacktrace->frames ) );
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.
Returns the number of frames in the trace object.
Calls $frame->as_string on each frame from top to bottom, producing output quite similar to the Carp module's cluck/confess methods.
$frame->as_string
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.
\%p
max_arg_length
If all the frames in a trace are skipped then this just returns the message passed to the constructor or the string "Trace begun".
message
"Trace begun"
Returns the message passed to the constructor. If this wasn't passed then this method returns undef.
Bugs may be submitted at https://github.com/houseabsolute/Devel-StackTrace/issues.
The source code repository for Devel-StackTrace can be found at https://github.com/houseabsolute/Devel-StackTrace.
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@urth.org, or use the button at https://houseabsolute.com/foss-donations/.
Dave Rolsky <autarch@urth.org>
Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
David Cantrell <david@cantrell.org.uk>
Graham Knop <haarg@haarg.org>
Ivan Bessarabov <ivan@bessarabov.ru>
Mark Fowler <mark@twoshortplanks.com>
Pali <pali@cpan.org>
Ricardo Signes <rjbs@cpan.org>
This software is Copyright (c) 2000 - 2024 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.
To install Devel::StackTrace, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Devel::StackTrace
CPAN shell
perl -MCPAN -e shell install Devel::StackTrace
For more information on module installation, please visit the detailed CPAN module installation guide.