Devel::StackTrace - An object representing a stack trace
version 2.04
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
the Devel::StackTrace::Frame manpage. 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 the Exception::Class::Base manpage class (part of
the Exception::Class manpage) 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.
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
the Devel::StackTrace::Frame manpage 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.
Returns the next the Devel::StackTrace::Frame manpage 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.
Returns the next the Devel::StackTrace::Frame manpage 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
the Devel::StackTrace::Frame manpage 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 the Devel::StackTrace::Frame manpage 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 ) );
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.
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".
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.
I am also usually active on IRC as 'autarch' on irc://irc.perl.org.
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 http://www.urth.org/~autarch/fs-donation.html.
Dave Rolsky <autarch@urth.org>
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.
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