/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: jan@swi-prolog.org WWW: http://www.swi-prolog.org Copyright (c) 2021-2023, SWI-Prolog Solutions b.v. 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_tools, [ (spy)/1, % :Spec (some users tend to define these as (nospy)/1, % :Spec an operator) nospyall/0, debugging/0, trap/1, % +Exception notrap/1 % +Exception ]). :- use_module(library(broadcast), [broadcast/1]). :- autoload(library(edinburgh), [debug/0]). :- autoload(library(gensym), [gensym/2]). :- multifile trap_alias/2. :- set_prolog_flag(generate_debug_info, false). /** User level debugging tools This library provides tools to control the Prolog debuggers. Traditionally this code was built-in. Because these tools are only required in (interactive) debugging sessions they have been moved into the library. */ %! prolog:debug_control_hook(+Action) % % Allow user-hooks in the Prolog debugger interaction. See the calls % below for the provided hooks. We use a single predicate with action % argument to avoid an uncontrolled poliferation of hooks. :- multifile prolog:debug_control_hook/1. % +Action :- meta_predicate spy(:), nospy(:). %! spy(:Spec) is det. %! nospy(:Spec) is det. %! nospyall is det. % % Set/clear spy-points. A successfully set or cleared spy-point is % reported using print_message/2, level `informational`, with one of % the following terms, where Spec is of the form M:Head. % % - spy(Spec) % - nospy(Spec) % % @see spy/1 and nospy/1 call the hook prolog:debug_control_hook/1 % to allow for alternative specifications of the thing to % debug. spy(Spec) :- '$notrace'(spy_(Spec)). spy_(_:X) :- var(X), throw(error(instantiation_error, _)). spy_(_:[]) :- !. spy_(M:[H|T]) :- !, spy(M:H), spy(M:T). spy_(Spec) :- prolog:debug_control_hook(spy(Spec)), !. spy_(Spec) :- '$find_predicate'(Spec, Preds), '$member'(PI, Preds), pi_to_head(PI, Head), '$define_predicate'(Head), '$spy'(Head), fail. spy_(_). nospy(Spec) :- '$notrace'(nospy_(Spec)). nospy_(_:X) :- var(X), throw(error(instantiation_error, _)). nospy_(_:[]) :- !. nospy_(M:[H|T]) :- !, nospy(M:H), nospy(M:T). nospy_(Spec) :- prolog:debug_control_hook(nospy(Spec)), !. nospy_(Spec) :- '$find_predicate'(Spec, Preds), '$member'(PI, Preds), pi_to_head(PI, Head), '$nospy'(Head), fail. nospy_(_). nospyall :- '$notrace'(nospyall_). nospyall_ :- prolog:debug_control_hook(nospyall), fail. nospyall_ :- spy_point(Head), '$nospy'(Head), fail. nospyall_. pi_to_head(M:PI, M:Head) :- !, pi_to_head(PI, Head). pi_to_head(Name/Arity, Head) :- functor(Head, Name, Arity). %! debugging is det. % % Report current status of the debugger. debugging :- '$notrace'(debugging_). debugging_ :- prolog:debug_control_hook(debugging), !. debugging_ :- ( current_prolog_flag(debug, true) -> print_message(informational, debugging(on)), findall(H, spy_point(H), SpyPoints), print_message(informational, spying(SpyPoints)) ; print_message(informational, debugging(off)) ), trapping, forall(debugging_hook, true). spy_point(Module:Head) :- current_predicate(_, Module:Head), '$get_predicate_attribute'(Module:Head, spy, 1), \+ predicate_property(Module:Head, imported_from(_)). %! debugging_hook % % Multifile hook that is called as forall(debugging_hook, true) and % that may be used to extend the information printed from other % debugging libraries. :- multifile debugging_hook/0. /******************************* * EXCEPTIONS * *******************************/ %! trap(+Formal) is det. %! notrap(+Formal) is det. % % Install a trap on error(Formal, Context) exceptions that unify. The % tracer is started when a matching exception is raised. This % predicate enables _debug mode_ using debug/0 to get more context % about the exception. Even with debug mode disabled exceptions are % still trapped and thus one may call nodebug/0 to run in normal mode % after installing a trap. Exceptions are trapped in any thread. Debug % mode is only enabled in the calling thread. To enable debug mode in % all threads use tdebug/0. % % Calling debugging/0 lists the enabled traps. The predicate notrap/1 % removes matching (unifying) traps. % % In many cases debugging an exception that is caught is as simple as % below (assuming run/0 starts your program). % % ``` % ?- trap(_). % ?- run. % ``` % % The multifile hook trap_alias/2 allow for defining short hands for % commonly used traps. Currently this defines % % - det % Trap determinism exceptions raised as a result of the det/1 % directive. % - => % Trap rule existence error exceptions. % % @see gtrap/1 to trap using the graphical debugger. % @see _Edit exceptions_ menu in PceEmacs and the graphical debugger % that provide a graphical frontend to trap exceptions. :- dynamic exception/4, % Name, Term, NotCaught, Caught installed/1. % ClauseRef trap(Error) :- '$notrace'(trap_(Error)). trap_(Spec) :- expand_trap(Spec, Formal), gensym(ex, Rule), asserta(exception(Rule, error(Formal, _), true, true)), print_message(informational, trap(Rule, error(Formal, _), true, true)), install_exception_hook, debug. notrap(Error) :- '$notrace'(notrap_(Error)). notrap_(Spec) :- expand_trap(Spec, Formal), Exception = error(Formal, _), findall(exception(Name, Exception, NotCaught, Caught), retract(exception(Name, error(Formal, _), Caught, NotCaught)), Trapping), print_message(informational, notrap(Trapping)). expand_trap(Var, _Formal), var(Var) => true. expand_trap(Alias, Formal), trap_alias(Alias, For) => Formal = For. expand_trap(Explicit, Formal) => Formal = Explicit. %! trap_alias(+Alias, -Error) % % Define short hands for commonly used exceptions. trap_alias(det, determinism_error(_Pred, _Declared, _Observed, property)). trap_alias(=>, existence_error(rule, _)). trapping :- findall(exception(Name, Term, NotCaught, Caught), exception(Name, Term, NotCaught, Caught), Trapping), print_message(information, trapping(Trapping)). :- dynamic prolog:prolog_exception_hook/5. :- multifile prolog:prolog_exception_hook/5. %! exception_hook(+ExIn, -ExOut, +Frame, +Catcher) is failure. % % Trap exceptions and consider whether or not to start the tracer. :- public exception_hook/5. exception_hook(Ex, Ex, _Frame, Catcher, _Debug) :- thread_self(Me), thread_property(Me, debug(true)), broadcast(debug(exception(Ex))), exception(_, Ex, NotCaught, Caught), !, ( Caught == true -> true ; Catcher == none, NotCaught == true ), trace, fail. %! install_exception_hook % % Make sure our handler is the first of the hook predicate. install_exception_hook :- installed(Ref), ( nth_clause(_, I, Ref) -> I == 1, ! % Ok, we are the first ; retractall(installed(Ref)), erase(Ref), % Someone before us! fail ). install_exception_hook :- asserta((prolog:prolog_exception_hook(Ex, Out, Frame, Catcher, Debug) :- exception_hook(Ex, Out, Frame, Catcher, Debug)), Ref), assert(installed(Ref)). /******************************* * MESSAGES * *******************************/ :- multifile prolog:message//1. prolog:message(trapping([])) --> [ 'No exception traps'-[] ]. prolog:message(trapping(Trapping)) --> [ 'Exception traps on'-[], nl ], trapping(Trapping). prolog:message(trap(_Rule, Error, _Caught, _NotCaught)) --> [ 'Installed trap for exception '-[] ], exception(Error), [ nl ]. prolog:message(notrap([])) --> [ 'No matching traps'-[] ]. prolog:message(notrap(Trapping)) --> [ 'Removed traps from exceptions'-[], nl ], trapping(Trapping). trapping([]) --> []. trapping([exception(_Rule, Error, _Caught, _NotCaught)|T]) --> [ ' '-[] ], exception(Error), [ nl ], trapping(T). exception(Term) --> { copy_term(Term, T2), numbervars(T2, 0, _, [singletons(true)]) }, [ '~p'-[T2] ].