diff options
| -rw-r--r-- | hash.c | 56 | ||||
| -rw-r--r-- | txr.1 | 20 |
2 files changed, 57 insertions, 19 deletions
@@ -1274,24 +1274,48 @@ static void do_weak_tables(void) case hash_weak_both: /* Sweep through all entries. Delete any which have keys or values that are garbage. */ - for (i = 0; i < h->modulus; i++) { - val *pchain = &h->table->v.vec[i]; - val *iter; - - for (iter = pchain; *iter; ) { - val entry = us_car(*iter); - if (!gc_is_reachable(us_car(entry)) || !gc_is_reachable(us_cdr(entry))) - { - *iter = us_cdr(*iter); + if (opt_compat && opt_compat <= 266) { + for (i = 0; i < h->modulus; i++) { + val *pchain = &h->table->v.vec[i]; + val *iter; + + for (iter = pchain; *iter; ) { + val entry = us_car(*iter); + if (!gc_is_reachable(us_car(entry)) || !gc_is_reachable(us_cdr(entry))) + { + *iter = us_cdr(*iter); #if CONFIG_EXTRA_DEBUGGING - if (!gc_is_reachable(us_car(entry)) && us_car(entry) == break_obj) - breakpt(); - if (!gc_is_reachable(us_cdr(entry)) && us_cdr(entry) == break_obj) - breakpt(); + if (!gc_is_reachable(us_car(entry)) && us_car(entry) == break_obj) + breakpt(); + if (!gc_is_reachable(us_cdr(entry)) && us_cdr(entry) == break_obj) + breakpt(); #endif - } else { - iter = us_cdr_p(*iter); - c++; + } else { + iter = us_cdr_p(*iter); + c++; + } + } + } + } else { + for (i = 0; i < h->modulus; i++) { + val *pchain = &h->table->v.vec[i]; + val *iter; + + for (iter = pchain; *iter; ) { + val entry = us_car(*iter); + if (!gc_is_reachable(us_car(entry)) && !gc_is_reachable(us_cdr(entry))) + { + *iter = us_cdr(*iter); +#if CONFIG_EXTRA_DEBUGGING + if (!gc_is_reachable(us_car(entry)) && us_car(entry) == break_obj) + breakpt(); + if (!gc_is_reachable(us_cdr(entry)) && us_cdr(entry) == break_obj) + breakpt(); +#endif + } else { + iter = us_cdr_p(*iter); + c++; + } } } } @@ -51063,9 +51063,16 @@ as a key in in one or more weak-key hash tables becomes unreachable, those hash entries disappear. This happens even if the values are themselves reachable. Vice versa, when an object appearing as a value in one or more weak-value hash tables becomes unreachable, those entries disappear, even if the keys are -reachable. When a hash table has both weak keys and weak values, then its -entries are removed when either keys or values become unreachable. In other -words, both the key and value must be reachable in order to retain the entry. +reachable. When a hash table has both weak keys and weak values, then an +entry is removed when neither its key nor its value is reachable. In other +words, if either the key or value is reachable, the entry is retained. +Note: this behavior differed in \*(TX 266 and earlier versions. + +If the keys of a weak-key hash table are reachable from the values, or if the +values of a weak-key hash table are reachable from the keys, then the weak +semantics is defeated for the affected entries: the hash table retains those +entries as if it were an ordinary table. A hash table with both weak keys and +values does not have this issue. An open traversal of a hash table is performed by the .code maphash @@ -83081,6 +83088,13 @@ of these version values, the described behaviors are provided if is given an argument which is equal or lower. For instance .code "-C 103" selects the behaviors described below for version 105, but not those for 102. +.IP 266 +Until \*(TX 266, hash tables with both weak values and keys are subject to +a conjunctive rule for entry retention: entries are retained if both the +key and value are reachable objects. If either the key or value is unreachable, +the entry is eligible for removal. The behavior changed in favor of a disjunctive +rule: the hash entry is retained if either the key or value is reachable. +A compatibility option value of 266 or lower restores the old behavior. .IP 265 Until \*(TX 265, the .code with-resources |