1Devel::StackTrace(3) User Contributed Perl Documentation Devel::StackTrace(3)
2
6 Devel::StackTrace - An object representing a stack trace
7
9 version 2.04
10
12 use Devel::StackTrace;
13 my $trace = Devel::StackTrace->new;
15 print $trace->as_string; # like carp
17 # from top (most recent) of stack to bottom.
19 while ( my $frame = $trace->next_frame ) {
20 print "Has args\n" if $frame->hasargs;
21 }
22 # from bottom (least recent) of stack to top.
24 while ( my $frame = $trace->prev_frame ) {
25 print "Sub: ", $frame->subroutine, "\n";
26 }
27
29 The "Devel::StackTrace" module contains two classes,
30 "Devel::StackTrace" and Devel::StackTrace::Frame. These objects
31 encapsulate the information that can retrieved via Perl's "caller"
32 function, as well as providing a simple interface to this data.
33 The "Devel::StackTrace" object contains a set of
35 "Devel::StackTrace::Frame" objects, one for each level of the stack.
36 The frames contain all the data available from "caller".
37 This code was created to support my Exception::Class::Base class (part
39 of Exception::Class) but may be useful in other contexts.
40
42 When describing the methods of the trace object, I use the words 'top'
43 and 'bottom'. In this context, the 'top' frame on the stack is the most
44 recent frame and the 'bottom' is the least recent.
45 Here's an example:
47 foo(); # bottom frame is here
49 sub foo {
51 bar();
52 }
53 sub bar {
55 Devel::StackTrace->new; # top frame is here.
56 }
57
59 This class provide the following methods:
60 Devel::StackTrace->new(%named_params)
62 Returns a new Devel::StackTrace object.
63 Takes the following parameters:
65 • frame_filter => $sub
67 By default, Devel::StackTrace will include all stack frames before
69 the call to its constructor.
70 However, you may want to filter out some frames with more
72 granularity than 'ignore_package' or 'ignore_class' allow.
73 You can provide a subroutine which is called with the raw frame
75 data for each frame. This is a hash reference with two keys,
76 "caller", and "args", both of which are array references. The
77 "caller" key is the raw data as returned by Perl's "caller"
78 function, and the "args" key are the subroutine arguments found in
79 @DB::args.
80 The filter should return true if the frame should be included, or
82 false if it should be skipped.
83 • filter_frames_early => $boolean
85 If this parameter is true, "frame_filter" will be called as soon as
87 the stacktrace is created, and before refs are stringified (if
88 "unsafe_ref_capture" is not set), rather than being filtered lazily
89 when Devel::StackTrace::Frame objects are first needed.
90 This is useful if you want to filter based on the frame's arguments
92 and want to be able to examine object properties, for example.
93 • ignore_package => $package_name OR \@package_names
95 Any frames where the package is one of these packages will not be
97 on the stack.
98 • ignore_class => $package_name OR \@package_names
100 Any frames where the package is a subclass of one of these packages
102 (or is the same package) will not be on the stack.
103 Devel::StackTrace internally adds itself to the 'ignore_package'
105 parameter, meaning that the Devel::StackTrace package is ALWAYS
106 ignored. However, if you create a subclass of Devel::StackTrace it
107 will not be ignored.
108 • skip_frames => $integer
110 This will cause this number of stack frames to be excluded from top
112 of the stack trace. This prevents the frames from being captured at
113 all, and applies before the "frame_filter", "ignore_package", or
114 "ignore_class" options, even with "filter_frames_early".
115 • unsafe_ref_capture => $boolean
117 If this parameter is true, then Devel::StackTrace will store
119 references internally when generating stacktrace frames.
120 This option is very dangerous, and should never be used with
122 exception objects. Using this option will keep any objects or
123 references alive past their normal lifetime, until the stack trace
124 object goes out of scope. It can keep objects alive even after
125 their "DESTROY" sub is called, resulting it it being called
126 multiple times on the same object.
127 If not set, Devel::StackTrace replaces any references with their
129 stringified representation.
130 • no_args => $boolean
132 If this parameter is true, then Devel::StackTrace will not store
134 caller arguments in stack trace frames at all.
135 • respect_overload => $boolean
137 By default, Devel::StackTrace will call "overload::AddrRef" to get
139 the underlying string representation of an object, instead of
140 respecting the object's stringification overloading. If you would
141 prefer to see the overloaded representation of objects in stack
142 traces, then set this parameter to true.
143 • max_arg_length => $integer
145 By default, Devel::StackTrace will display the entire argument for
147 each subroutine call. Setting this parameter causes truncates each
148 subroutine argument's string representation if it is longer than
149 this number of characters.
150 • message => $string
152 By default, Devel::StackTrace will use 'Trace begun' as the message
154 for the first stack frame when you call "as_string". You can supply
155 an alternative message using this option.
156 • indent => $boolean
158 If this parameter is true, each stack frame after the first will
160 start with a tab character, just like "Carp::confess".
161 $trace->next_frame
163 Returns the next Devel::StackTrace::Frame object on the stack, going
164 down. If this method hasn't been called before it returns the first
165 frame. It returns "undef" when it reaches the bottom of the stack and
166 then resets its pointer so the next call to "$trace->next_frame" or
167 "$trace->prev_frame" will work properly.
168 $trace->prev_frame
170 Returns the next Devel::StackTrace::Frame object on the stack, going
171 up. If this method hasn't been called before it returns the last frame.
172 It returns undef when it reaches the top of the stack and then resets
173 its pointer so the next call to "$trace->next_frame" or
174 "$trace->prev_frame" will work properly.
175 $trace->reset_pointer
177 Resets the pointer so that the next call to "$trace->next_frame" or
178 "$trace->prev_frame" will start at the top or bottom of the stack, as
179 appropriate.
180 $trace->frames
182 When this method is called with no arguments, it returns a list of
183 Devel::StackTrace::Frame objects. They are returned in order from top
184 (most recent) to bottom.
185 This method can also be used to set the object's frames if you pass it
187 a list of Devel::StackTrace::Frame objects.
188 This is useful if you want to filter the list of frames in ways that
190 are more complex than can be handled by the "$trace->filter_frames"
191 method:
192 $stacktrace->frames( my_filter( $stacktrace->frames ) );
194 $trace->frame($index)
196 Given an index, this method returns the relevant frame, or undef if
197 there is no frame at that index. The index is exactly like a Perl
198 array. The first frame is 0 and negative indexes are allowed.
199 $trace->frame_count
201 Returns the number of frames in the trace object.
202 $trace->as_string(\%p)
204 Calls "$frame->as_string" on each frame from top to bottom, producing
205 output quite similar to the Carp module's cluck/confess methods.
206 The optional "\%p" parameter only has one option. The "max_arg_length"
208 parameter truncates each subroutine argument's string representation if
209 it is longer than this number of characters.
210 If all the frames in a trace are skipped then this just returns the
212 "message" passed to the constructor or the string "Trace begun".
213 $trace->message
215 Returns the message passed to the constructor. If this wasn't passed
216 then this method returns "undef".
217
219 Bugs may be submitted at
220 <https://github.com/houseabsolute/Devel-StackTrace/issues>.
221 I am also usually active on IRC as 'autarch' on "irc://irc.perl.org".
223
225 The source code repository for Devel-StackTrace can be found at
226 <https://github.com/houseabsolute/Devel-StackTrace>.
227
229 If you'd like to thank me for the work I've done on this module, please
230 consider making a "donation" to me via PayPal. I spend a lot of free
231 time creating free software, and would appreciate any support you'd
232 care to offer.
233 Please note that I am not suggesting that you must do this in order for
235 me to continue working on this particular software. I will continue to
236 do so, inasmuch as I have in the past, for as long as it interests me.
237 Similarly, a donation made in this way will probably not make me work
239 on this software much more, unless I get so many donations that I can
240 consider working on free software full time (let's all have a chuckle
241 at that together).
242 To donate, log into PayPal and send money to autarch@urth.org, or use
244 the button at <http://www.urth.org/~autarch/fs-donation.html>.
245
247 Dave Rolsky <autarch@urth.org>
248
250 • Dagfinn Ilmari Mannsåker <ilmari@ilmari.org>
251 • David Cantrell <david@cantrell.org.uk>
253 • Graham Knop <haarg@haarg.org>
255 • Ivan Bessarabov <ivan@bessarabov.ru>
257 • Mark Fowler <mark@twoshortplanks.com>
259 • Pali <pali@cpan.org>
261 • Ricardo Signes <rjbs@cpan.org>
263
265 This software is Copyright (c) 2000 - 2019 by David Rolsky.
266 This is free software, licensed under:
268 The Artistic License 2.0 (GPL Compatible)
270 The full text of the license can be found in the LICENSE file included
272 with this distribution.
273perl v5.34.0 2022-01-21 Devel::StackTrace(3)