guile/test-suite/tests/gc.test

;;;; gc.test --- test guile's garbage collection    -*- scheme -*-
;;;; Copyright (C) 2000, 2001, 2004, 2006, 2007, 2008, 2009,
;;;;   2011, 2012, 2013 Free Software Foundation, Inc.
;;;;
;;;; This library is free software; you can redistribute it and/or
;;;; modify it under the terms of the GNU Lesser General Public
;;;; License as published by the Free Software Foundation; either
;;;; version 3 of the License, or (at your option) any later version.
;;;; 
;;;; This library is distributed in the hope that it will be useful,
;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
;;;; Lesser General Public License for more details.
;;;; 
;;;; You should have received a copy of the GNU Lesser General Public
;;;; License along with this library; if not, write to the Free Software
;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

(define-module (tests gc)
  #:use-module (ice-9 documentation)
  #:use-module (test-suite lib)
  #:use-module ((system base compile) #:select (compile)))


;; Some of these tests verify that things are collectable.  As we use a
;; third-party conservative collector, we really can't guarantee that --
;; we can try, but on some platforms, on some versions (possibly), the
;; test might fail.  But we don't want that to stop the build.  So,
;; instead of failing, throw 'unresolved.
;;
(define (maybe-gc-flakiness result)
  (or result
      (throw 'unresolved)))

;;;
;;; miscellaneous
;;;


(define (documented? object)
  (not (not (object-documentation object))))

;; In guile 1.6.4 this test bombed, due to the record in h being collected
;; by the gc, but not removed from h, leaving "x" as a freed cell.
;; The usual correct result here is for x to be #f, but there's always a
;; chance gc will mark something used when it isn't, so we allow x to be a
;; record too.
(pass-if "weak-values versus records"
  (let ((rec-type (make-record-type 'foo '()))
	(h        (make-weak-value-hash-table 61)))
    (hash-set! h "foo" ((record-constructor rec-type)))
    (gc)
    (let ((x (hash-ref h "foo")))
      (or (not x)
	  ((record-predicate rec-type) x)))))


;;;
;;; 
;;;

(with-test-prefix "gc"

  (pass-if "after-gc-hook gets called"
    (let* ((foo #f)
	   (thunk (lambda () (set! foo #t))))
      (add-hook! after-gc-hook thunk)
      (gc)
      (remove-hook! after-gc-hook thunk)
      foo))

  (pass-if "Unused modules are removed"
    (let* ((guard (make-guardian))
           (total 1000))

      (for-each (lambda (x) (guard (make-module))) (iota total))

      ;; Avoid false references to the modules on the stack.
      (clear-stale-stack-references)

      (gc)
      (gc)   ;; twice: have to kill the weak vectors.
      (gc)   ;; thrice: because the test doesn't succeed with only
      ;; one gc round. not sure why.

      (maybe-gc-flakiness
       (= (let lp ((i 0))
            (if (guard)
                (lp (1+ i))
                i))
          total))))

  (pass-if "Lexical vars are collectable"
    (let ((l (compile
              '(begin
                 (define guardian (make-guardian))
                 (let ((f (list 'foo)))
                   (guardian f))
                 ((@ (test-suite lib) clear-stale-stack-references))
                 (gc)(gc)(gc)
                 (guardian))
              ;; Prevent the optimizer from propagating f.
              #:opts '(#:partial-eval? #f))))
      (maybe-gc-flakiness (equal? l '(foo))))))