1/* Part of SWI-Prolog 2 3 Author: Jan Wielemaker 4 E-mail: J.Wielemaker@vu.nl 5 WWW: http://www.swi-prolog.org 6 Copyright (c) 2014-2015, VU University Amsterdam 7 All rights reserved. 8 9 Redistribution and use in source and binary forms, with or without 10 modification, are permitted provided that the following conditions 11 are met: 12 13 1. Redistributions of source code must retain the above copyright 14 notice, this list of conditions and the following disclaimer. 15 16 2. Redistributions in binary form must reproduce the above copyright 17 notice, this list of conditions and the following disclaimer in 18 the documentation and/or other materials provided with the 19 distribution. 20 21 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 29 CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 31 ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 32 POSSIBILITY OF SUCH DAMAGE. 33*/ 34 35:- module(modules, 36 [ in_temporary_module/3 % ?Module, :Setup, :Goal 37 ]). 38 39 40/** <module> Module utility predicates 41*/ 42 43:- meta_predicate 44 in_temporary_module(, , ). 45 46%! in_temporary_module(?Module, :Setup, :Goal) 47% 48% Run Goal on temporary loaded sources and discard the module and 49% loaded predicates after completion. This predicate performs the 50% following steps: 51% 52% 1. If Module is unbound, create a unique identifier for it. 53% 2. Turn Module into a _temporary_ module using set_module/1. 54% Note that this requires the module to be non-existent or 55% empty. If Module is specified, it should typically be set 56% to a unique value as obtained from e.g. uuid/1. 57% 3. Run Setup in the context of Module. 58% 4. If setup succeeded possible choice points are discarded 59% and Goal is started. 60% 61% The logical result of this predicate is the same as 62% `(Setup@Module -> Goal@Module)`, i.e., both Setup and Goal are 63% resolved relative to the current module, but executed in the 64% context of Module. If Goal must be called in Module, use 65% `call(Goal)`. 66% 67% The module and all its predicates are destroyed after Goal 68% terminates, as defined by setup_call_cleanup/3. 69% 70% *Discussion* This predicate is intended to load programs in an 71% isolated environment and reclaim all resources. This 72% unfortunately is incomplete: 73% 74% - Running the code may leave side effects such as creating 75% records, flags, changing Prolog flags, etc. The system 76% has no provisions to track this. 77% - So called _functors_ (name/arity pairs) are not yet subject 78% to garbage collection. Functors are both used to define 79% predicates and to create compound terms. 80% 81% @see library(sandbox) determines whether unknown goals are safe 82% to call. 83% @see load_files/2 offers the option sandboxed(true) to load code 84% from unknown sources safely. 85 86in_temporary_module(Module, Setup, Goal) :- 87 setup_call_cleanup( 88 prepare_temporary_module(Module), 89 ( @(Setup, Module) 90 -> @(Goal, Module) 91 ), 92 '$destroy_module'(Module)). 93 94prepare_temporary_module(Module) :- 95 var(Module), 96 !, 97 ( repeat, 98 I is random(1<<63), 99 atom_concat('tmp-', I, Module), 100 set_module(Module:class(temporary)) 101 -> true 102 ). 103prepare_temporary_module(Module) :- 104 set_module(Module:class(temporary)).