/* Part of SWI-Prolog Author: Jan Wielemaker E-mail: J.Wielemaker@vu.nl WWW: http://www.swi-prolog.org Copyright (c) 2014-2021, VU University Amsterdam 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(modules, [ in_temporary_module/3, % ?Module, :Setup, :Goal current_temporary_module/1 % ?Module ]). /** Module utility predicates */ :- meta_predicate in_temporary_module(?, 0, 0). %! in_temporary_module(?Module, :Setup, :Goal) % % Run Goal on temporary loaded sources and discard the module and % loaded predicates after completion. This predicate performs the % following steps: % % 1. If Module is unbound, create a unique identifier for it. % 2. Turn Module into a _temporary_ module using set_module/1. % Note that this requires the module to be non-existent or % empty. If Module is specified, it should typically be set % to a unique value as obtained from e.g. uuid/1. % 3. Run Setup in the context of Module. % 4. If setup succeeded possible choice points are discarded % and Goal is started. % % The logical result of this predicate is the same as % `(Setup@Module -> Goal@Module)`, i.e., both Setup and Goal are % resolved relative to the current module, but executed in the % context of Module. If Goal must be called in Module, use % `call(Goal)`. % % The module and all its predicates are destroyed after Goal % terminates, as defined by setup_call_cleanup/3. % % *Discussion* This predicate is intended to load programs in an % isolated environment and reclaim all resources. This % unfortunately is incomplete: % % - Running the code may leave side effects such as creating % records, flags, changing Prolog flags, etc. The system % has no provisions to track this. % - So called _functors_ (name/arity pairs) are not yet subject % to garbage collection. Functors are both used to define % predicates and to create compound terms. % % @see library(sandbox) determines whether unknown goals are safe % to call. % @see load_files/2 offers the option sandboxed(true) to load code % from unknown sources safely. in_temporary_module(Module, Setup, Goal) :- setup_call_cleanup( prepare_temporary_module(Module), ( @(Setup, Module) -> @(Goal, Module) ), destroy_module(Module)). prepare_temporary_module(Module) :- var(Module), !, ( thread_id(Tid), repeat, I is random(1<<62), atomic_list_concat([tmp, Tid, I], -, Module), catch(set_module(Module:class(temporary)), error(permission_error(_,_,_),_), fail) -> b_setval('$tmp_module', Module) ). prepare_temporary_module(Module) :- set_module(Module:class(temporary)), b_setval('$tmp_module', Module). :- if(current_prolog_flag(threads, true)). thread_id(Id) :- thread_self(Self), thread_property(Self, id(Id)). :- else. thread_id(main). :- endif. destroy_module(Module) :- retractall(system:'$load_context_module'(_File, Module, _Options)), '$destroy_module'(Module). %! current_temporary_module(-Module) is semidet. % % True when we are executing in the given temporary module context. current_temporary_module(Module) :- nb_current('$tmp_module', Module).