-/* Copyright (C) 1998, 1999, 2000 Free Software Foundation, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2, or (at your option)
- * any later version.
- *
- * This program 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 General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this software; see the file COPYING. If not, write to
- * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
- * Boston, MA 02111-1307 USA
- *
- * As a special exception, the Free Software Foundation gives permission
- * for additional uses of the text contained in its release of GUILE.
- *
- * The exception is that, if you link the GUILE library with other files
- * to produce an executable, this does not by itself cause the
- * resulting executable to be covered by the GNU General Public License.
- * Your use of that executable is in no way restricted on account of
- * linking the GUILE library code into it.
- *
- * This exception does not however invalidate any other reasons why
- * the executable file might be covered by the GNU General Public License.
- *
- * This exception applies only to the code released by the
- * Free Software Foundation under the name GUILE. If you copy
- * code from other Free Software Foundation releases into a copy of
- * GUILE, as the General Public License permits, the exception does
- * not apply to the code that you add in this way. To avoid misleading
- * anyone as to the status of such modified files, you must delete
- * this exception notice from them.
- *
- * If you write modifications of your own for GUILE, it is your choice
- * whether to permit this exception to apply to your modifications.
- * If you do not wish that, delete this exception notice. */
-
-/* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
- gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
-
-\f
-
-/* This is an implementation of guardians as described in
- * R. Kent Dybvig, Carl Bruggeman, and David Eby (1993) "Guardians in
- * a Generation-Based Garbage Collector" ACM SIGPLAN Conference on
- * Programming Language Design and Implementation, June 1993
- * ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/pubs/guardians.ps.gz
- *
- * Author: Michael N. Livshin
- * Modified by: Mikael Djurfeldt
- */
-
-
-#include "libguile/_scm.h"
-#include "libguile/ports.h"
-#include "libguile/print.h"
-#include "libguile/smob.h"
-
-#include "libguile/validate.h"
-#include "libguile/guardians.h"
-
-
-/* The live and zombies FIFOs are implemented as tconcs as described
- in Dybvig's paper. This decouples addition and removal of elements
- so that no synchronization between these needs to take place.
-*/
-
-typedef struct tconc_t
-{
- SCM head;
- SCM tail;
-} tconc_t;
-
-#define TCONC_EMPTYP(tc) (SCM_EQ_P ((tc).head, (tc).tail))
-
-#define TCONC_IN(tc, obj, pair) \
-do { \
- SCM_SETCAR ((tc).tail, obj); \
- SCM_SETCAR (pair, SCM_BOOL_F); \
- SCM_SETCDR (pair, SCM_EOL); \
- SCM_SETCDR ((tc).tail, pair); \
- (tc).tail = pair; \
-} while (0)
-
-#define TCONC_OUT(tc, res) \
-do { \
- (res) = SCM_CAR ((tc).head); \
- (tc).head = SCM_CDR ((tc).head); \
-} while (0)
-
-
-static long tc16_guardian;
-
-typedef struct guardian_t
-{
- tconc_t live;
- tconc_t zombies;
- struct guardian_t *next;
-} guardian_t;
-
-#define GUARDIAN(x) ((guardian_t *) SCM_CELL_WORD_1 (x))
-#define GUARDIAN_LIVE(x) (GUARDIAN (x)->live)
-#define GUARDIAN_ZOMBIES(x) (GUARDIAN (x)->zombies)
-#define GUARDIAN_NEXT(x) (GUARDIAN (x)->next)
-
-
-/* during the gc mark phase, live guardians are linked into a list here. */
-static guardian_t *first_live_guardian = NULL;
-static guardian_t **current_link_field = NULL;
-
-
-/* mark a guardian by adding it to the live guardian list. */
-static SCM
-guardian_mark (SCM ptr)
-{
- *current_link_field = GUARDIAN (ptr);
- current_link_field = &GUARDIAN_NEXT (ptr);
- GUARDIAN_NEXT (ptr) = NULL;
-
- /* the objects protected by the guardian are not marked here: that
- would prevent them from ever getting collected. instead marking
- is done at the end of the mark phase by scm_guardian_zombify. */
- return SCM_BOOL_F;
-}
-
-
-static scm_sizet
-guardian_free (SCM ptr)
-{
- scm_must_free (GUARDIAN (ptr));
- return sizeof (guardian_t);
-}
-
-
-static int
-guardian_print (SCM g, SCM port, scm_print_state *pstate)
-{
- scm_puts ("#<guardian live objs: ", port);
- scm_display (scm_length (SCM_CDR (GUARDIAN_LIVE (g).head)), port);
- scm_puts (" zombies: ", port);
- scm_display (scm_length (SCM_CDR (GUARDIAN_ZOMBIES (g).head)), port);
- scm_puts (">", port);
-
- return 1;
-}
-
-
-/* This is the Scheme entry point for each guardian: If arg is an object, it's
- * added to the guardian's live list. If arg is unbound, the next available
- * zombified object (or #f if none) is returned.
- */
-static SCM
-guardian_apply (SCM guardian, SCM arg)
-{
- if (!SCM_UNBNDP (arg))
- {
- scm_guard (guardian, arg);
- return SCM_UNSPECIFIED;
- }
- else
- return scm_get_one_zombie (guardian);
-}
-
-
-void
-scm_guard (SCM guardian, SCM obj)
-{
- if (!SCM_IMP (obj))
- {
- SCM z;
-
- SCM_NEWCELL (z);
-
- /* This critical section barrier will be replaced by a mutex. */
- SCM_DEFER_INTS;
- TCONC_IN (GUARDIAN_LIVE (guardian), obj, z);
- SCM_ALLOW_INTS;
- }
-}
-
-
-SCM
-scm_get_one_zombie (SCM guardian)
-{
- SCM res = SCM_BOOL_F;
-
- /* This critical section barrier will be replaced by a mutex. */
- SCM_DEFER_INTS;
- if (!TCONC_EMPTYP (GUARDIAN_ZOMBIES (guardian)))
- TCONC_OUT (GUARDIAN_ZOMBIES (guardian), res);
- SCM_ALLOW_INTS;
- return res;
-}
-
-
-SCM_DEFINE (scm_make_guardian, "make-guardian", 0, 0, 0,
- (),
- "Create a new guardian.\n"
- "A guardian protects a set of objects from garbage collection,\n"
- "allowing a program to apply cleanup or other actions.\n\n"
-
- "make-guardian returns a procedure representing the guardian.\n"
- "Calling the guardian procedure with an argument adds the\n"
- "argument to the guardian's set of protected objects.\n"
- "Calling the guardian procedure without an argument returns\n"
- "one of the protected objects which are ready for garbage\n"
- "collection or @code{#f} if no such object is available.\n"
- "Objects which are returned in this way are removed from\n"
- "the guardian.\n\n"
-
- "See R. Kent Dybvig, Carl Bruggeman, and David Eby (1993)\n"
- "\"Guardians in a Generation-Based Garbage Collector\".\n"
- "ACM SIGPLAN Conference on Programming Language Design\n"
- "and Implementation, June 1993.")
-#define FUNC_NAME s_scm_make_guardian
-{
- guardian_t *g = SCM_MUST_MALLOC_TYPE (guardian_t);
- SCM z1 = scm_cons (SCM_BOOL_F, SCM_EOL);
- SCM z2 = scm_cons (SCM_BOOL_F, SCM_EOL);
- SCM z;
-
- /* A tconc starts out with one tail pair. */
- g->live.head = g->live.tail = z1;
- g->zombies.head = g->zombies.tail = z2;
-
- SCM_NEWSMOB (z, tc16_guardian, g);
-
- return z;
-}
-#undef FUNC_NAME
-
-
-/* called before gc mark phase begins to initialise the live guardian list. */
-static void *
-guardian_gc_init (void *dummy1, void *dummy2, void *dummy3)
-{
- current_link_field = &first_live_guardian;
- first_live_guardian = NULL;
-
- return 0;
-}
-
-
-/* this is called by the garbage collector between the mark and sweep
- phases. for each marked guardian, it moves any unmarked object in
- its live list (tconc) to its zombie list (tconc). */
-static void *
-guardian_zombify (void *dummy1, void *dummy2, void *dummy3)
-{
- guardian_t *first_guardian;
- guardian_t **link_field = &first_live_guardian;
-
- /* Note that new guardians may be stuck on the end of the live
- guardian list as we run this loop. As we move unmarked objects
- to the zombie list and mark them, we may find some guarded
- guardians. The guardian mark function will stick them on the end
- of this list, so they'll be processed properly. */
-
- do {
- guardian_t *g;
-
- first_guardian = *link_field;
- link_field = current_link_field;
-
- /* first, scan all the guardians that are currently known to be live
- and move their unmarked objects to zombie lists. */
-
- for (g = first_guardian; g; g = g->next)
- {
- SCM tconc_tail = g->live.tail;
- SCM *prev_ptr = &g->live.head;
- SCM pair = g->live.head;
-
- while (! SCM_EQ_P (pair, tconc_tail))
- {
- SCM next_pair = SCM_CDR (pair);
-
- if (SCM_NMARKEDP (SCM_CAR (pair)))
- {
- /* got you, zombie! */
-
- /* out of the live list! */
- *prev_ptr = next_pair;
-
- /* into the zombie list! */
- TCONC_IN (g->zombies, SCM_CAR (pair), pair);
- }
- else
- prev_ptr = SCM_CDRLOC (pair);
-
- pair = next_pair;
- }
-
- /* Mark the cells of the live list (yes, the cells in the list,
- even though we don't care about objects pointed to by the list
- cars, since we know they are already marked). */
- for (pair = g->live.head; !SCM_NULLP (pair); pair = SCM_CDR (pair))
- SCM_SETGCMARK (pair);
- }
-
- /* ghouston: Doesn't it seem a bit disturbing that if a zombie
- is returned to full life after getting returned from the
- guardian procedure, it may reference objects which are in a
- guardian's zombie list? Is it not necessary to move such
- zombies back to the live list, to avoid allowing the
- guardian procedure to return an object which is referenced,
- so not collectable? The paper doesn't give this
- impression.
-
- cmm: the paper does explicitly say that an object that is
- guarded more than once should be returned more than once.
- I believe this covers the above scenario. */
-
- /* Preserve the zombies in their undead state, by marking to
- prevent collection. Note that this may uncover zombified
- guardians -- if so, they'll be processed in the next loop. */
- for (g = first_guardian; g != *link_field; g = g->next)
- scm_gc_mark (g->zombies.head);
- } while (current_link_field != link_field);
-
- return 0;
-}
-
-
-void
-scm_init_guardian()
-{
- tc16_guardian = scm_make_smob_type ("guardian", 0);
- scm_set_smob_mark (tc16_guardian, guardian_mark);
- scm_set_smob_free (tc16_guardian, guardian_free);
- scm_set_smob_print (tc16_guardian, guardian_print);
- scm_set_smob_apply (tc16_guardian, guardian_apply, 0, 1, 0);
-
- scm_c_hook_add (&scm_before_mark_c_hook, guardian_gc_init, 0, 0);
- scm_c_hook_add (&scm_before_sweep_c_hook, guardian_zombify, 0, 0);
-
-#ifndef SCM_MAGIC_SNARFER
-#include "libguile/guardians.x"
-#endif
-}
-
-/*
- Local Variables:
- c-file-style: "gnu"
- End:
-*/
+/* Copyright (C) 1998,1999,2000,2001 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 2.1 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
+ */
+
+\f
+
+/* This is an implementation of guardians as described in
+ * R. Kent Dybvig, Carl Bruggeman, and David Eby (1993) "Guardians in
+ * a Generation-Based Garbage Collector" ACM SIGPLAN Conference on
+ * Programming Language Design and Implementation, June 1993
+ * ftp://ftp.cs.indiana.edu/pub/scheme-repository/doc/pubs/guardians.ps.gz
+ *
+ * Original design: Mikael Djurfeldt
+ * Original implementation: Michael Livshin
+ * Hacked on since by: everybody
+ *
+ * By this point, the semantics are actually quite different from
+ * those described in the abovementioned paper. The semantic changes
+ * are there to improve safety and intuitiveness. The interface is
+ * still (mostly) the one described by the paper, however.
+ *
+ * Boiled down again: Marius Vollmer
+ *
+ * Now they should again behave like those described in the paper.
+ * Scheme guardians should be simple and friendly, not like the greedy
+ * monsters we had...
+ */
+
+
+#include "libguile/_scm.h"
+#include "libguile/async.h"
+#include "libguile/ports.h"
+#include "libguile/print.h"
+#include "libguile/smob.h"
+#include "libguile/validate.h"
+#include "libguile/root.h"
+#include "libguile/hashtab.h"
+#include "libguile/weaks.h"
+#include "libguile/deprecation.h"
+#include "libguile/eval.h"
+
+#include "libguile/guardians.h"
+
+
+/* The live and zombies FIFOs are implemented as tconcs as described
+ in Dybvig's paper. This decouples addition and removal of elements
+ so that no synchronization between these needs to take place.
+*/
+
+typedef struct t_tconc
+{
+ SCM head;
+ SCM tail;
+} t_tconc;
+
+#define TCONC_EMPTYP(tc) (scm_is_eq ((tc).head, (tc).tail))
+
+#define TCONC_IN(tc, obj, pair) \
+do { \
+ SCM_SETCAR ((tc).tail, obj); \
+ SCM_SET_CELL_OBJECT_1 (pair, SCM_EOL); \
+ SCM_SET_CELL_OBJECT_0 (pair, SCM_BOOL_F); \
+ SCM_SETCDR ((tc).tail, pair); \
+ (tc).tail = pair; \
+} while (0)
+
+#define TCONC_OUT(tc, res) \
+do { \
+ (res) = SCM_CAR ((tc).head); \
+ (tc).head = SCM_CDR ((tc).head); \
+} while (0)
+
+
+static scm_t_bits tc16_guardian;
+
+typedef struct t_guardian
+{
+ t_tconc live;
+ t_tconc zombies;
+ struct t_guardian *next;
+} t_guardian;
+
+#define GUARDIAN_P(x) SCM_SMOB_PREDICATE(tc16_guardian, x)
+#define GUARDIAN_DATA(x) ((t_guardian *) SCM_CELL_WORD_1 (x))
+
+static t_guardian *guardians;
+
+void
+scm_i_init_guardians_for_gc ()
+{
+ guardians = NULL;
+}
+
+/* mark a guardian by adding it to the live guardian list. */
+static SCM
+guardian_mark (SCM ptr)
+{
+ t_guardian *g = GUARDIAN_DATA (ptr);
+ g->next = guardians;
+ guardians = g;
+
+ return SCM_BOOL_F;
+}
+
+/* Identify inaccessible objects and move them from the live list to
+ the zombie list. An object is inaccessible when it is unmarked at
+ this point. Therefore, the inaccessible objects are not marked yet
+ since that would prevent them from being recognized as
+ inaccessible.
+
+ The pairs that form the life list itself are marked, tho.
+*/
+void
+scm_i_identify_inaccessible_guardeds ()
+{
+ t_guardian *g;
+
+ for (g = guardians; g; g = g->next)
+ {
+ SCM pair, next_pair;
+ SCM *prev_ptr;
+
+ for (pair = g->live.head, prev_ptr = &g->live.head;
+ !scm_is_eq (pair, g->live.tail);
+ pair = next_pair)
+ {
+ SCM obj = SCM_CAR (pair);
+ next_pair = SCM_CDR (pair);
+ if (!SCM_GC_MARK_P (obj))
+ {
+ /* Unmarked, move to 'inaccessible' list.
+ */
+ *prev_ptr = next_pair;
+ TCONC_IN (g->zombies, obj, pair);
+ }
+ else
+ {
+ SCM_SET_GC_MARK (pair);
+ prev_ptr = SCM_CDRLOC (pair);
+ }
+ }
+ SCM_SET_GC_MARK (pair);
+ }
+}
+
+int
+scm_i_mark_inaccessible_guardeds ()
+{
+ t_guardian *g;
+ int again = 0;
+
+ /* We never need to see the guardians again that are processed here,
+ so we clear the list. Calling scm_gc_mark below might find new
+ guardians, however (and other things), and we inform the GC about
+ this by returning non-zero. See scm_mark_all in gc-mark.c
+ */
+
+ g = guardians;
+ guardians = NULL;
+
+ for (; g; g = g->next)
+ {
+ SCM pair;
+
+ for (pair = g->zombies.head;
+ !scm_is_eq (pair, g->zombies.tail);
+ pair = SCM_CDR (pair))
+ {
+ if (!SCM_GC_MARK_P (pair))
+ {
+ scm_gc_mark (SCM_CAR (pair));
+ SCM_SET_GC_MARK (pair);
+ again = 1;
+ }
+ }
+ SCM_SET_GC_MARK (pair);
+ }
+ return again;
+}
+
+static size_t
+guardian_free (SCM ptr)
+{
+ scm_gc_free (GUARDIAN_DATA (ptr), sizeof (t_guardian), "guardian");
+ return 0;
+}
+
+static int
+guardian_print (SCM guardian, SCM port, scm_print_state *pstate SCM_UNUSED)
+{
+ t_guardian *g = GUARDIAN_DATA (guardian);
+
+ scm_puts ("#<guardian ", port);
+ scm_uintprint ((scm_t_bits) g, 16, port);
+
+ scm_puts (" (reachable: ", port);
+ scm_display (scm_length (SCM_CDR (g->live.head)), port);
+ scm_puts (" unreachable: ", port);
+ scm_display (scm_length (SCM_CDR (g->zombies.head)), port);
+ scm_puts (")", port);
+
+ scm_puts (">", port);
+
+ return 1;
+}
+
+static void
+scm_i_guard (SCM guardian, SCM obj)
+{
+ t_guardian *g = GUARDIAN_DATA (guardian);
+
+ if (!SCM_IMP (obj))
+ {
+ SCM z;
+ z = scm_cons (SCM_BOOL_F, SCM_BOOL_F);
+ TCONC_IN (g->live, obj, z);
+ }
+}
+
+static SCM
+scm_i_get_one_zombie (SCM guardian)
+{
+ t_guardian *g = GUARDIAN_DATA (guardian);
+ SCM res = SCM_BOOL_F;
+
+ if (!TCONC_EMPTYP (g->zombies))
+ TCONC_OUT (g->zombies, res);
+
+ return res;
+}
+
+/* This is the Scheme entry point for each guardian: If OBJ is an
+ * object, it's added to the guardian's live list. If OBJ is unbound,
+ * the next available unreachable object (or #f if none) is returned.
+ *
+ * If the second optional argument THROW_P is true (the default), then
+ * an error is raised if GUARDIAN is greedy and OBJ is already greedily
+ * guarded. If THROW_P is false, #f is returned instead of raising the
+ * error, and #t is returned if everything is fine.
+ */
+static SCM
+guardian_apply (SCM guardian, SCM obj, SCM throw_p)
+{
+#if ENABLE_DEPRECATED
+ if (!SCM_UNBNDP (throw_p))
+ scm_c_issue_deprecation_warning
+ ("Using the 'throw?' argument of a guardian is deprecated "
+ "and ineffective.");
+#endif
+
+ if (!SCM_UNBNDP (obj))
+ {
+ scm_i_guard (guardian, obj);
+ return SCM_UNSPECIFIED;
+ }
+ else
+ return scm_i_get_one_zombie (guardian);
+}
+
+SCM_DEFINE (scm_make_guardian, "make-guardian", 0, 0, 0,
+ (),
+"Create a new guardian. A guardian protects a set of objects from\n"
+"garbage collection, allowing a program to apply cleanup or other\n"
+"actions.\n"
+"\n"
+"@code{make-guardian} returns a procedure representing the guardian.\n"
+"Calling the guardian procedure with an argument adds the argument to\n"
+"the guardian's set of protected objects. Calling the guardian\n"
+"procedure without an argument returns one of the protected objects\n"
+"which are ready for garbage collection, or @code{#f} if no such object\n"
+"is available. Objects which are returned in this way are removed from\n"
+"the guardian.\n"
+"\n"
+"You can put a single object into a guardian more than once and you can\n"
+"put a single object into more than one guardian. The object will then\n"
+"be returned multiple times by the guardian procedures.\n"
+"\n"
+"An object is eligible to be returned from a guardian when it is no\n"
+"longer referenced from outside any guardian.\n"
+"\n"
+"There is no guarantee about the order in which objects are returned\n"
+"from a guardian. If you want to impose an order on finalization\n"
+"actions, for example, you can do that by keeping objects alive in some\n"
+"global data structure until they are no longer needed for finalizing\n"
+"other objects.\n"
+"\n"
+"Being an element in a weak vector, a key in a hash table with weak\n"
+"keys, or a value in a hash table with weak value does not prevent an\n"
+"object from being returned by a guardian. But as long as an object\n"
+"can be returned from a guardian it will not be removed from such a\n"
+"weak vector or hash table. In other words, a weak link does not\n"
+"prevent an object from being considered collectable, but being inside\n"
+"a guardian prevents a weak link from being broken.\n"
+"\n"
+"A key in a weak key hash table can be though of as having a strong\n"
+"reference to its associated value as long as the key is accessible.\n"
+"Consequently, when the key only accessible from within a guardian, the\n"
+"reference from the key to the value is also considered to be coming\n"
+"from within a guardian. Thus, if there is no other reference to the\n"
+ "value, it is eligible to be returned from a guardian.\n")
+#define FUNC_NAME s_scm_make_guardian
+{
+ t_guardian *g = scm_gc_malloc (sizeof (t_guardian), "guardian");
+ SCM z1 = scm_cons (SCM_BOOL_F, SCM_EOL);
+ SCM z2 = scm_cons (SCM_BOOL_F, SCM_EOL);
+ SCM z;
+
+ /* A tconc starts out with one tail pair. */
+ g->live.head = g->live.tail = z1;
+ g->zombies.head = g->zombies.tail = z2;
+
+ g->next = NULL;
+
+ SCM_NEWSMOB (z, tc16_guardian, g);
+
+ return z;
+}
+#undef FUNC_NAME
+
+void
+scm_init_guardians ()
+{
+ tc16_guardian = scm_make_smob_type ("guardian", 0);
+ scm_set_smob_mark (tc16_guardian, guardian_mark);
+ scm_set_smob_free (tc16_guardian, guardian_free);
+ scm_set_smob_print (tc16_guardian, guardian_print);
+#if ENABLE_DEPRECATED
+ scm_set_smob_apply (tc16_guardian, guardian_apply, 0, 2, 0);
+#else
+ scm_set_smob_apply (tc16_guardian, guardian_apply, 0, 1, 0);
+#endif
+
+#include "libguile/guardians.x"
+}
+
+/*
+ Local Variables:
+ c-file-style: "gnu"
+ End:
+*/
HCoop / bpt / guile.git / blobdiff