seq_iter: fix gc issues.

* lib.h (struct seq_iter_ops): New operation, mark.
(seq_iter_ops_init): Default the mark operation to
seq_iter_mark_op.
(seq_iter_ops_init_nomark): New macro.

* lib.c (seq_iter_mark_op): New static function.
(si_range_cnum_ops, si_range_chr_ops, si_rev_range_cnum_ops,
si_rev_range_chr_ops, si_chr_ops): Initialize with
seq_iter_ops_init_nomark so that the iterator has no mark
operation. All other iterator types have the above new static
function as their mark op.
(seq_iter_mark): Simplified: if the iterator has a mark op,
call it.
(seq_next, iter_step): If the iterator has a mark op, that
means that the seq_get operation is likely replacing one heap
object with another, and so mut(iter) must be called to inform
the garbage collector of the assignment.

1 files changed, 3 insertions, 1 deletions

diff --git a/lib.h b/lib.h
index 3365183c..76ad19b2 100644
--- a/lib.h
+++ b/lib.h
@@ -421,9 +421,11 @@ typedef struct seq_iter {
 struct seq_iter_ops {
   int (*get)(struct seq_iter *, val *pval);
   int (*peek)(struct seq_iter *, val *pval);
+  void (*mark)(struct seq_iter *);
 };
 
-#define seq_iter_ops_init(get, peek) { get, peek }
+#define seq_iter_ops_init(get, peek) { get, peek, seq_iter_mark_op }
+#define seq_iter_ops_init_nomark(get, peek) { get, peek, 0 }
 
 extern const seq_kind_t seq_kind_tab[MAXTYPE+1];