As the FSF advises, 'There is no legal significance to using the
three-character sequence “(C)”, but it does no harm.' It does take up
space though! For that reason, we remove it here from our C files.
hashtable and guardian machinery but call the relevant functions
directly.
* guardians.h, guardians.c, deprecated.h,
deprecated.c (scm_destroy_guardian_x, scm_guardian_greedy_p,
scm_guardian_destroyed_p, scm_guard, scm_get_one_zombie):
Deprecated and moved into deprecated.[ch].
* guardians.h, guardians.c: Mostly rewritten.
(scm_i_init_guardians_for_gc,
scm_i_identify_inaccessible_guardeds,
scm_i_mark_inaccessible_guardeds): New.
* weaks.h, weaks.c (SCM_I_WVECT_TYPE, SCM_I_SET_WVECT_TYPE): New.
(SCM_I_WVECT_N_ITEMS, SCM_I_SET_WVECT_N_ITEMS): New.
(SCM_WVECTF_NOSCAN, SCM_WVECT_NOSCAN_P): Removed.
(scm_weaks_prehistory): Removed.
(scm_i_init_weak_vectors_for_gc, scm_i_mark_weak_vector,
scm_i_mark_weak_vectors_non_weaks,
scm_i_remove_weaks_from_weak_vectors, scm_i_remove_weaks): New.
(scm_weak_vector_gc_init, scm_mark_weak_vector_spines,
scm_scan_weak_vectors): Removed.
* hashtab.h (scm_i_scan_weak_hashtables): New.
* hashtab.c (make_hash_table, scm_i_rehash): Do not use
SCM_WVECTF_NOSCAN.
(hashtable_print): Use SCM_HASHTABLE_N_ITEMS instead of
t->n_items.
(scan_weak_hashtables, scm_i_scan_weak_hashtables): Renamed former
to latter. Do not scan the alists themselves, this is done by the
weak vector code now. Just update the element count.
* vectors.h (SCM_I_WVECT_TYPE, SCM_I_WVECT_EXTRA): Renamed former
to latter. The type is now only part of the cell word.
(SCM_I_SET_WVECT_TYPE, SCM_I_SET_WVECT_EXTRA): Likewise.
* init.c (scm_i_init_guile): Do not call scm_weaks_prehistory.
SET_GREEDY, LISTED_P, SET_LISTED, CLR_LISTED, DESTROYED_P,
SET_DESTROYED): new defines/macros.
(GUARDIAN_LIVE, GUARDIAN_ZOMBIES, GUARDIAN_NEXT): deleted.
(add_to_live_list): takes a `guardian_t *' now, not SCM.
(guardian_print): print more info.
(guardian_apply): check if the guardian is destroyed, and throw an
error if so. take one more optional argument `throw_p'.
(scm_guard): depending on the value of `throw_p', return a boolean
result.
(scm_get_one_zombie): remove redundant property test.
(guardian_t): represent the various (currently 3, I hope nothing
more gets added) boolean fields as bit flags.
(scm_guardian_destroyed_p, scm_guardian_greedy_p): new predicates.
(scm_destroy_guardian_x): new procedure.
* guardians.h: added prototypes for `scm_guardian_greedy_p' and
`scm_guardian_destroyed_p'. changed prototype for `scm_guard'.
`scm_gc_mark', but doesn't mark the argument itself. defined
using an arrangement similar to that in eval.c: `scm_gc_mark' and
`scm_gc_mark_dependencies' are derived from the same "template"
by ugly preprocessor magic.
* gc.h: added prototype for `scm_gc_mark_dependencies'.
* init.c (scm_init_guile_1): call the renamed
`scm_init_guardians'.
* guardians.h: changed prototypes for `scm_make_guardian' and
`scm_init_guardians'.
* guardians.c (guardian_t): added new fields `greedy_p' and
`listed_p'.
(GUARDIAN_P): predicate that says whether its argument is a
guardian.
(GUARDIAN_GREEDY_P, GUARDIAN_LISTED_P): new predicates.
(greedy_guardians, sharing_guardians): new variables. hold the
greedy and sharing live guardian lists, respectively.
(first_live_guardian, current_link_field): removed.
(greedily_guarded_prop): new variable. holds the "is greedily
guarded" object property.
(self_centered_zombies): new variable. stores guarded objects
that are parts of cycles.
(add_to_live_list): new function, introduced to decouple marking a
guardian and adding it to the live list.
(guardian_mark): call `add_to_live_list'.
(guardian_print): print whether the guardian is greedy or not.
also change "live" and "zombie" to "reachable" and "unreachable"
respectively, to be less confusing.
(scm_guard): if the guardian is greedy, test whether the object is
already greedily marked. throw an error if so.
(scm_get_one_zombie): if the guardian is greedy, remove the
"greedily guarded" property from the object.
(scm_make_guardian): add a new optional boolean argument which
says whether the guardian is greedy or sharing.
(guardian_gc_init): init the new live lists.
(mark_dependencies): new function.
(mark_and_zombify): new function.
(guardian_zombify): reworked to support the new guardian
semantics. move some logic to `mark_dependencies' and
`mark_and_zombify'.
(whine_about_self_centered_zombies): new function. installed in
the `after-gc-hook' to complain about guarded objects which are
parts of cycles.
(scm_init_guardians): init the new stuff. renamed from
`scm_init_guardian'.
scm_guardian_gc_init, scm_guardian_zombify, scm_guard,
scm_get_one_zombie, scm_init_guardian): 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.
