NAME¶
Devel::StackTrace - An object representing a stack trace
VERSION¶
version 1.34
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
"no_refs" is true), 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".
- •
- no_refs => $boolean
If this parameter is true, then Devel::StackTrace will not store references
internally when generating stacktrace frames. This lets your objects go
out of scope.
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>
COPYRIGHT AND LICENSE¶
This software is Copyright (c) 2014 by Dave Rolsky.
This is free software, licensed under:
The Artistic License 2.0 (GPL Compatible)