/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: jan@swi-prolog.org WWW: http://www.swi-prolog.org Copyright (c) 2021, 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 (nospy)/1, % :Spec (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]). /** 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(_:X) :- var(X), throw(error(instantiation_error, _)). spy(_:[]) :- !. spy(M:[H|T]) :- !, spy(M:H), spy(M:T). spy(Spec) :- notrace(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(_:X) :- var(X), throw(error(instantiation_error, _)). nospy(_:[]) :- !. nospy(M:[H|T]) :- !, nospy(M:H), nospy(M:T). nospy(Spec) :- notrace(prolog:debug_control_hook(nospy(Spec))), !. nospy(Spec) :- '$find_predicate'(Spec, Preds), '$member'(PI, Preds), pi_to_head(PI, Head), '$nospy'(Head), fail. nospy(_). nospyall :- notrace(prolog:debug_control_hook(nospyall)), fail. nospyall :- spy_point(Head), '$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(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. spy_point(Module:Head) :- current_predicate(_, Module:Head), '$get_predicate_attribute'(Module:Head, spy, 1), \+ predicate_property(Module:Head, imported_from(_)). /******************************* * EXCEPTIONS * *******************************/ %! trap(+Exception) is det. %! notrap(+Exception) is det. % % Install a trap on error(Formal, Context) exceptions that unify with % Exception. 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. % % The predicate notrap/1 removes matching (unifying) traps. % % @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) :- gensym(ex, Rule), asserta(exception(Rule, error(Error, _), true, true)), print_message(informational, trap(Rule, error(Error, _), true, true)), install_exception_hook, debug. notrap(Error) :- Exception = error(Error, _), findall(exception(Name, Exception, NotCaught, Caught), retract(exception(Name, error(Error, _), Caught, NotCaught)), Trapping), print_message(informational, notrap(Trapping)). trapping :- findall(exception(Name, Term, NotCaught, Caught), exception(Name, Term, NotCaught, Caught), Trapping), print_message(information, trapping(Trapping)). :- dynamic user:prolog_exception_hook/4. %! exception_hook(+ExIn, -ExOut, +Frame, +Catcher) is failure. % % Trap exceptions and consider whether or not to start the tracer. :- public exception_hook/4. exception_hook(Ex, Ex, _Frame, Catcher) :- 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((user:prolog_exception_hook(Ex, Out, Frame, Catcher) :- exception_hook(Ex, Out, Frame, Catcher)), 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] ].