Ensure that a hash reorganization doesn't take place

during a traversal, which could cause items to be visited
twice or skipped.

* gc.c (full_gc): Changed from static to exter (full_gc): Changed to
internal linkage.

* gc.h (full_gc): Declared.

* hash.c (struct hash): New member, usecount.
(struct hash_iter): New member, next.
(reachable_iters): New static variable.
(hash_mark): Reset the usecount of every reachable hash table.
(hash_iter_mark): Add every reachable iterator to reachable_iters
list.
(make_hash, make_similar_hash, copy_hash): Initialize usecount.
(gethash_c): Do not call hash_grow if usecount is nonzero.
(hash_begin): Initialize next field of hash_iter to null.
Increment use count on hash table.
(hash_next): When traversal ends, release use count, and
null out the hash table reference.
(do_weak_tables): New static function.
(do_iters): New static function.
(hash_process_weak): Weak hash processing logic moved
to do_weak_tables. Also calls do_iters.

* txr.1: Describe hash table traversal, and the assurances
and caveats about inserting and deleting items.

1 files changed, 1 insertions, 1 deletions

diff --git a/gc.c b/gc.c
index d3dd1f3c..0f7fc785 100644
--- a/gc.c
+++ b/gc.c
@@ -90,7 +90,7 @@ static val mutobj[MUTOBJ_VEC_SIZE];
 static int mutobj_idx;
 static val freshobj[FRESHOBJ_VEC_SIZE];
 static int freshobj_idx;
-static int full_gc;
+int full_gc;
 #endif
 
 #if EXTRA_DEBUGGING