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Moved weak pair code into `weaks.[ch]'.

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* libguile/hashtab.c: Don't include <gc/gc_typed.h> and <gc/gc.h>.
  Updated users of weak
  (wcar_cell_descr): Removed.
  (wcdr_cell_descr): Removed.
  (scm_weak_car_cell): Removed.
  (scm_weak_cdr_cell): Removed.
  (scm_doubly_weak_cell): Removed.
  (SCM_WEAK_CELL_*_DELETED_P): Removed.
  (SCM_WEAK_CELL_WORD): Removed.
  (SCM_WEAK_CELL_C[AD]R): Removed.
  (scm_hashtab_prehistory): Don't initialize weak pairs.

* libguile/init.c (scm_i_init_guile): Invoke `scm_weaks_prehistory ()'
  before `scm_hashtab_prehistory ()' in order to initialize weak pairs.

* libguile/weaks.c: Include <gc/gc.h> and <gc/gc_typed.h>.
  (wc[ad]r_cell_descr): New.
  (scm_weak_c[ad]r_pair): New.
  (scm_doubly_weak_pair): New.
  (scm_weaks_prehistory): New.

* libguile/weaks.h (scm_weak_c[ad]r_pair): New declaration.
  (scm_doubly_weak_pair): New declaration.
  (SCM_WEAK_PAIR_WORD_DELETED_P): New.
  (SCM_WEAK_PAIR_CAR_DELETED_P): New.
  (SCM_WEAK_PAIR_CDR_DELETED_P): New.
  (SCM_WEAK_PAIR_DELETED_P): New.
  (SCM_WEAK_PAIR_WORD): New.
  (SCM_WEAK_PAIR_CAR): New.
  (SCM_WEAK_PAIR_CDR): New.

git-archimport-id: lcourtes@laas.fr--2005-libre/guile-core--boehm-gc--1.9--patch-39
This commit is contained in:
Ludovic Courtes 2006-06-25 22:42:19 +00:00 • committed by Ludovic Courtès
commit 986ec82209
4 changed files with 151 additions and 125 deletions
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136
libguile/hashtab.c
View file

@ -31,9 +31,6 @@
#include "libguile/validate.h"
#include "libguile/hashtab.h"
#include <gc/gc.h>
#include <gc/gc_typed.h>
@ -85,104 +82,12 @@ static char *s_hashtable = "hashtable";
/* Weak cells for use in weak alist vectors (aka. weak hash tables).
/* Helper functions and macros to deal with weak pairs.
We have weal-car cells, weak-cdr cells, and doubly weak cells. In weak
cells, the weak component(s) are not scanned for pointers and are
registered as disapperaring links; therefore, the weak component may be
set to NULL by the garbage collector when no other reference to that word
exist. Thus, we use `scm_fixup_weak_alist ()' to check for nullified weak
cells and remove them. */
/* Type descriptors for weak-c[ad]r cells. */
static GC_descr wcar_cell_descr, wcdr_cell_descr;
static SCM
scm_weak_car_cell (SCM car, SCM cdr)
{
scm_t_cell *cell;
cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell),
wcar_cell_descr);
cell->word_0 = car;
cell->word_1 = cdr;
if (SCM_NIMP (car))
{
/* Weak car cells make sense iff the car is non-immediate. */
GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_0,
(GC_PTR)SCM_UNPACK (car));
}
return (SCM_PACK (cell));
}
static SCM
scm_weak_cdr_cell (SCM car, SCM cdr)
{
scm_t_cell *cell;
cell = (scm_t_cell *)GC_malloc_explicitly_typed (sizeof (*cell),
wcdr_cell_descr);
cell->word_0 = car;
cell->word_1 = cdr;
if (SCM_NIMP (cdr))
{
/* Weak cdr cells make sense iff the cdr is non-immediate. */
GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_1,
(GC_PTR)SCM_UNPACK (cdr));
}
return (SCM_PACK (cell));
}
static SCM
scm_doubly_weak_cell (SCM car, SCM cdr)
{
/* Doubly weak cells shall not be scanned at all for pointers. */
scm_t_cell *cell = (scm_t_cell *)scm_gc_malloc_pointerless (sizeof (*cell),
"weak cell");
cell->word_0 = car;
cell->word_1 = cdr;
if (SCM_NIMP (car))
{
GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_0,
(GC_PTR)SCM_UNPACK (car));
}
if (SCM_NIMP (cdr))
{
GC_GENERAL_REGISTER_DISAPPEARING_LINK ((GC_PTR)&cell->word_1,
(GC_PTR)SCM_UNPACK (cdr));
}
return (SCM_PACK (cell));
}
/* Testing the weak component(s) of a cell for reachability. */
#define SCM_WEAK_CELL_WORD_DELETED_P(_cell, _word) \
(SCM_CELL_OBJECT ((_cell), (_word)) == SCM_PACK (NULL))
#define SCM_WEAK_CELL_CAR_DELETED_P(_cell) \
(SCM_WEAK_CELL_WORD_DELETED_P ((_cell), 0))
#define SCM_WEAK_CELL_CDR_DELETED_P(_cell) \
(SCM_WEAK_CELL_WORD_DELETED_P ((_cell), 1))
#define SCM_WEAK_CELL_DELETED_P(_cell) \
((SCM_WEAK_CELL_CAR_DELETED_P (_cell)) \
|| (SCM_WEAK_CELL_CDR_DELETED_P (_cell)))
/* Accessing the components of a weak cell. */
#define SCM_WEAK_CELL_WORD(_cell, _word) \
((SCM_WEAK_CELL_WORD_DELETED_P ((_cell), (_word))) \
? SCM_BOOL_F : SCM_CAR (pair))
#define SCM_WEAK_CELL_CAR(_cell) (SCM_WEAK_CELL_WORD ((_cell), 0))
#define SCM_WEAK_CELL_CDR(_cell) (SCM_WEAK_CELL_WORD ((_cell), 1))
Weak pairs need to be accessed very carefully since their components can
be nullified by the GC when the object they refer to becomes unreachable.
Hence the macros and functions below that detect such weak pairs within
buckets and remove them. */
/* Return a ``usable'' version of ALIST, an alist of weak pairs. By
@ -204,8 +109,8 @@ scm_fixup_weak_alist (SCM alist, size_t *removed_items)
if (scm_is_pair (pair))
{
if ((SCM_WEAK_CELL_CAR_DELETED_P (pair))
|| (SCM_WEAK_CELL_CDR_DELETED_P (pair)))
if ((SCM_WEAK_PAIR_CAR_DELETED_P (pair))
|| (SCM_WEAK_PAIR_CDR_DELETED_P (pair)))
{
/* Remove from ALIST weak pair PAIR whose car/cdr has been
nullified by the GC. */
@ -369,7 +274,7 @@ scm_i_rehash (SCM table,
handle = SCM_CAR (cell);
ls = SCM_CDR (ls);
if (SCM_WEAK_CELL_DELETED_P (handle))
if (SCM_WEAK_PAIR_DELETED_P (handle))
/* HANDLE is a nullified weak pair: skip it. */
continue;
@ -609,11 +514,11 @@ scm_hash_fn_create_handle_x (SCM table, SCM obj, SCM init, unsigned long (*hash_
/* FIXME: We don't support weak alist vectors. */
/* Use a weak cell. */
if (SCM_HASHTABLE_DOUBLY_WEAK_P (table))
handle = scm_doubly_weak_cell (obj, init);
handle = scm_doubly_weak_pair (obj, init);
else if (SCM_HASHTABLE_WEAK_KEY_P (table))
handle = scm_weak_car_cell (obj, init);
handle = scm_weak_car_pair (obj, init);
else
handle = scm_weak_cdr_cell (obj, init);
handle = scm_weak_cdr_pair (obj, init);
}
else
/* Use a regular, non-weak cell. */
@ -1106,7 +1011,7 @@ scm_internal_hash_fold (SCM (*fn) (), void *closure, SCM init, SCM table)
if (IS_WEAK_THING (table))
{
if (SCM_WEAK_CELL_DELETED_P (handle))
if (SCM_WEAK_PAIR_DELETED_P (handle))
{
/* We hit a weak pair whose car/cdr has become
unreachable: unlink it from the bucket. */
@ -1264,23 +1169,6 @@ SCM_DEFINE (scm_hash_map_to_list, "hash-map->list", 2, 0, 0,
void
scm_hashtab_prehistory ()
{
/* Initialize weak cells. */
GC_word wcar_cell_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 };
GC_word wcdr_cell_bitmap[GC_BITMAP_SIZE (scm_t_cell)] = { 0 };
/* In a weak-car cell, only the second word must be scanned for
pointers. */
GC_set_bit (wcar_cell_bitmap, GC_WORD_OFFSET (scm_t_cell, word_1));
wcar_cell_descr = GC_make_descriptor (wcar_cell_bitmap,
GC_WORD_LEN (scm_t_cell));
/* Conversely, in a weak-cdr cell, only the first word must be scanned for
pointers. */
GC_set_bit (wcdr_cell_bitmap, GC_WORD_OFFSET (scm_t_cell, word_0));
wcdr_cell_descr = GC_make_descriptor (wcdr_cell_bitmap,
GC_WORD_LEN (scm_t_cell));
/* Initialize the hashtab SMOB type. */
scm_tc16_hashtable = scm_make_smob_type (s_hashtable, 0);
scm_set_smob_print (scm_tc16_hashtable, hashtable_print);