This file is indexed.

/usr/lib/swi-prolog/library/debug.pl is in swi-prolog-nox 7.6.4+dfsg-1build1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
/*  Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        J.Wielemaker@vu.nl
    WWW:           http://www.swi-prolog.org
    Copyright (c)  2002-2016, University of Amsterdam
                              VU University Amsterdam
    All rights reserved.

    Redistribution and use in source and binary forms, with or without
    modification, are permitted provided that the following conditions
    are met:

    1. Redistributions of source code must retain the above copyright
       notice, this list of conditions and the following disclaimer.

    2. Redistributions in binary form must reproduce the above copyright
       notice, this list of conditions and the following disclaimer in
       the documentation and/or other materials provided with the
       distribution.

    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
    FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
    COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
    BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
    LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
    CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
    ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    POSSIBILITY OF SUCH DAMAGE.
*/

:- module(prolog_debug,
          [ debug/3,                    % +Topic, +Format, :Args
            debug/1,                    % +Topic
            nodebug/1,                  % +Topic
            debugging/1,                % ?Topic
            debugging/2,                % ?Topic, ?Bool
            list_debug_topics/0,
            debug_message_context/1,    % (+|-)What

            assertion/1                 % :Goal
          ]).
:- use_module(library(error)).
:- use_module(library(lists)).
:- set_prolog_flag(generate_debug_info, false).

:- meta_predicate
    assertion(0),
    debug(+,+,:).

:- multifile prolog:assertion_failed/2.
:- dynamic   prolog:assertion_failed/2.

/*:- use_module(library(prolog_stack)).*/ % We use the autoloader if needed

%:- set_prolog_flag(generate_debug_info, false).

:- dynamic
    debugging/3,                    % Topic, Enabled, To
    debug_context/1.

debug_context(thread).

/** <module> Print debug messages and test assertions

This library is a replacement for  format/3 for printing debug messages.
Messages are assigned a _topic_. By   dynamically  enabling or disabling
topics the user can  select  desired   messages.  Debug  statements  are
removed when the code is compiled for optimization.

See manual for details. With XPCE, you can use the call below to start a
graphical monitoring tool.

==
?- prolog_ide(debug_monitor).
==

Using the predicate assertion/1 you  can   make  assumptions  about your
program explicit, trapping the debugger if the condition does not hold.

@author Jan Wielemaker
*/

%!  debugging(+Topic) is semidet.
%!  debugging(-Topic) is nondet.
%!  debugging(?Topic, ?Bool) is nondet.
%
%   Examine debug topics. The form debugging(+Topic)  may be used to
%   perform more complex debugging tasks.   A typical usage skeleton
%   is:
%
%     ==
%           (   debugging(mytopic)
%           ->  <perform debugging actions>
%           ;   true
%           ),
%           ...
%     ==
%
%   The other two calls are intended to examine existing and enabled
%   debugging tokens and are typically not used in user programs.

debugging(Topic) :-
    debugging(Topic, true, _To).

debugging(Topic, Bool) :-
    debugging(Topic, Bool, _To).

%!  debug(+Topic) is det.
%!  nodebug(+Topic) is det.
%
%   Add/remove a topic from being   printed.  nodebug(_) removes all
%   topics. Gives a warning if the topic is not defined unless it is
%   used from a directive. The latter allows placing debug topics at
%   the start of a (load-)file without warnings.
%
%   For debug/1, Topic can be  a  term   Topic  >  Out, where Out is
%   either a stream or  stream-alias  or   a  filename  (atom). This
%   redirects debug information on this topic to the given output.

debug(Topic) :-
    with_mutex(prolog_debug, debug(Topic, true)).
nodebug(Topic) :-
    with_mutex(prolog_debug, debug(Topic, false)).

debug(Spec, Val) :-
    debug_target(Spec, Topic, Out),
    (   (   retract(debugging(Topic, Enabled0, To0))
        *-> update_debug(Enabled0, To0, Val, Out, Enabled, To),
            assert(debugging(Topic, Enabled, To)),
            fail
        ;   (   prolog_load_context(file, _)
            ->  true
            ;   print_message(warning, debug_no_topic(Topic))
            ),
            update_debug(false, [], Val, Out, Enabled, To),
            assert(debugging(Topic, Enabled, To))
        )
    ->  true
    ;   true
    ).

debug_target(Spec, Topic, To) :-
    nonvar(Spec),
    Spec = (Topic > To),
    !.
debug_target(Topic, Topic, -).

update_debug(_, To0, true, -, true, To) :-
    !,
    ensure_output(To0, To).
update_debug(true, To0, true, Out, true, Output) :-
    !,
    (   memberchk(Out, To0)
    ->  Output = To0
    ;   append(To0, [Out], Output)
    ).
update_debug(false, _, true, Out, true, [Out]) :- !.
update_debug(_, _, false, -, false, []) :- !.
update_debug(true, [Out], false, Out, false, []) :- !.
update_debug(true, To0, false, Out, true, Output) :-
    !,
    delete(To0, Out, Output).

ensure_output([], [user_error]) :- !.
ensure_output(List, List).

%!  debug_topic(+Topic) is det.
%
%   Declare a topic for debugging.  This can be used to find all
%   topics available for debugging.

debug_topic(Topic) :-
    (   debugging(Registered, _, _),
        Registered =@= Topic
    ->  true
    ;   assert(debugging(Topic, false, []))
    ).

%!  list_debug_topics is det.
%
%   List currently known debug topics and their setting.

list_debug_topics :-
    format(user_error, '~`-t~45|~n', []),
    format(user_error, '~w~t ~w~35| ~w~n',
           ['Debug Topic', 'Activated', 'To']),
    format(user_error, '~`-t~45|~n', []),
    (   debugging(Topic, Value, To),
        format(user_error, '~w~t ~w~35| ~w~n', [Topic, Value, To]),
        fail
    ;   true
    ).

%!  debug_message_context(+What) is det.
%
%   Specify additional context for debug messages.   What  is one of
%   +Context or -Context, and Context is  one of =thread=, =time= or
%   time(Format),  where  Format  is    a  format specification  for
%   format_time/3 (default is =|%T.%3f|=).  Initially, debug/3 shows
%   only thread information.

debug_message_context(+Topic) :-
    !,
    valid_topic(Topic, Del, Add),
    retractall(debug_context(Del)),
    assert(debug_context(Add)).
debug_message_context(-Topic) :-
    !,
    valid_topic(Topic, Del, _),
    retractall(debug_context(Del)).
debug_message_context(Term) :-
    type_error(debug_message_context, Term).

valid_topic(thread, thread, thread) :- !.
valid_topic(time, time(_), time('%T.%3f')) :- !.
valid_topic(time(Format), time(_), time(Format)) :- !.
valid_topic(X, _, _) :-
    domain_error(debug_message_context, X).


%!  debug(+Topic, +Format, :Args) is det.
%
%   Format a message if debug topic  is enabled. Similar to format/3
%   to =user_error=, but only prints if   Topic is activated through
%   debug/1. Args is a  meta-argument  to   deal  with  goal for the
%   @-command.   Output   is   first    handed     to    the    hook
%   prolog:debug_print_hook/3.  If  this  fails,    Format+Args   is
%   translated  to  text   using    the   message-translation   (see
%   print_message/2) for the  term  debug(Format,   Args)  and  then
%   printed to every matching destination   (controlled  by debug/1)
%   using print_message_lines/3.
%
%   The message is preceded by '% ' and terminated with a newline.
%
%   @see    format/3.

debug(Topic, Format, Args) :-
    debugging(Topic, true, To),
    !,
    print_debug(Topic, To, Format, Args).
debug(_, _, _).


%!  prolog:debug_print_hook(+Topic, +Format, +Args) is semidet.
%
%   Hook called by debug/3.  This  hook   is  used  by the graphical
%   frontend that can be activated using prolog_ide/1:
%
%     ==
%     ?- prolog_ide(debug_monitor).
%     ==

:- multifile
    prolog:debug_print_hook/3.

print_debug(Topic, _To, Format, Args) :-
    prolog:debug_print_hook(Topic, Format, Args),
    !.
print_debug(_, [], _, _) :- !.
print_debug(Topic, To, Format, Args) :-
    phrase('$messages':translate_message(debug(Format, Args)), Lines),
    (   member(T, To),
        debug_output(T, Stream),
        with_output_to(
            Stream,
            print_message_lines(current_output, kind(debug(Topic)), Lines)),
        fail
    ;   true
    ).


debug_output(user, user_error) :- !.
debug_output(Stream, Stream) :-
    is_stream(Stream),
    !.
debug_output(File, Stream) :-
    open(File, append, Stream,
         [ close_on_abort(false),
           alias(File),
           buffer(line)
         ]).


                 /*******************************
                 *           ASSERTION          *
                 *******************************/

%!  assertion(:Goal) is det.
%
%   Acts similar to C assert()  macro.  It   has  no  effect if Goal
%   succeeds. If Goal fails or throws    an exception, the following
%   steps are taken:
%
%     * call prolog:assertion_failed/2.  If prolog:assertion_failed/2
%       fails, then:
%
%       - If this is an interactive toplevel thread, print a
%         message, the stack-trace, and finally trap the debugger.
%       - Otherwise, throw error(assertion_error(Reason, G),_) where
%         Reason is one of =fail= or the exception raised.

assertion(G) :-
    \+ \+ catch(G,
                Error,
                assertion_failed(Error, G)),

    !.
assertion(G) :-
    assertion_failed(fail, G),
    assertion_failed.               % prevent last call optimization.

assertion_failed(Reason, G) :-
    prolog:assertion_failed(Reason, G),
    !.
assertion_failed(Reason, _) :-
    assertion_rethrow(Reason),
    !,
    throw(Reason).
assertion_failed(Reason, G) :-
    print_message(error, assertion_failed(Reason, G)),
    backtrace(10),
    (   current_prolog_flag(break_level, _) % interactive thread
    ->  trace
    ;   throw(error(assertion_error(Reason, G), _))
    ).

assertion_failed.

assertion_rethrow(time_limit_exceeded).
assertion_rethrow('$aborted').

%!  assume(:Goal) is det.
%
%   Acts similar to C assert() macro.  It has no effect of Goal
%   succeeds.  If Goal fails it prints a message, a stack-trace
%   and finally traps the debugger.
%
%   @deprecated     Use assertion/1 in new code.

                 /*******************************
                 *           EXPANSION          *
                 *******************************/

%       The optimise_debug flag  defines whether  Prolog  optimizes
%       away assertions and  debug/3 statements.  Values are =true=
%       (debug is optimized away),  =false= (debug is retained) and
%       =default= (debug optimization is dependent on the optimise
%       flag).

optimise_debug :-
    (   current_prolog_flag(optimise_debug, true)
    ->  true
    ;   current_prolog_flag(optimise_debug, default),
        current_prolog_flag(optimise, true)
    ->  true
    ).

:- multifile
    system:goal_expansion/2.

system:goal_expansion(debug(Topic,_,_), true) :-
    (   optimise_debug
    ->  true
    ;   debug_topic(Topic),
        fail
    ).
system:goal_expansion(debugging(Topic), fail) :-
    (   optimise_debug
    ->  true
    ;   debug_topic(Topic),
        fail
    ).
system:goal_expansion(assertion(_), true) :-
    optimise_debug.
system:goal_expansion(assume(_), true) :-
    print_message(informational,
                  compatibility(renamed(assume/1, assertion/1))),
    optimise_debug.


                 /*******************************
                 *            MESSAGES          *
                 *******************************/

:- multifile
    prolog:message/3.

prolog:message(assertion_failed(_, G)) -->
    [ 'Assertion failed: ~q'-[G] ].
prolog:message(debug(Fmt, Args)) -->
    show_thread_context,
    show_time_context,
    [ Fmt-Args ].
prolog:message(debug_no_topic(Topic)) -->
    [ '~q: no matching debug topic (yet)'-[Topic] ].

show_thread_context -->
    { debug_context(thread),
      thread_self(Me),
      report_as(Me, Name)
    },
    [ '[Thread ~w] '-[Name] ].
show_thread_context -->
    [].

report_as(main, _) :-
    !,
    fail.
report_as(Alias, Alias) :-
    atom(Alias),
    !.
report_as(Handle, Id) :-
    catch(thread_property(Handle, id(Id)), _, fail),
    !.
report_as(Thread, Thread).

show_time_context -->
    { debug_context(time(Format)),
      get_time(Now),
      format_time(string(S), Format, Now)
    },
    [ '[~w] '-[S] ].
show_time_context -->
    [].

                 /*******************************
                 *             HOOKS            *
                 *******************************/

%!  prolog:assertion_failed(+Reason, +Goal) is semidet.
%
%   This hook is called if the Goal  of assertion/1 fails. Reason is
%   unified with either =fail= if Goal simply failed or an exception
%   call otherwise. If this hook  fails,   the  default behaviour is
%   activated.  If  the  hooks  throws  an   exception  it  will  be
%   propagated into the caller of assertion/1.


                 /*******************************
                 *            SANDBOX           *
                 *******************************/

:- multifile sandbox:safe_meta/2.

sandbox:safe_meta(prolog_debug:assertion(X), [X]).