parse/eval: use weak-both hash tables.

This addresses the problem that
a4c376979d15323ad729e92e41ba43768e8dc163
tried to fix.

* eval.c (eval_init): Make all the top-level binding tables,
top_fb, top_vb, top_mb, top_smb, special and builtin,
weak-both tables: keys and values are weak.
This way, the entries disappear if both key and value
are unreachable, even if they refer to each other.
(eval_compat_fixup): In 266 or earlier compat mode, weak-both
tables don't have the right semantics, so we tweak
the tables to weak-key tables.

* parser.c (parse_init): Same treatment for
stream_parser_hash. We want an entry to disappear from the
hash if neither the parser nor the stream are reachable.
(parse_compat_fixup): New function.

* parser.h (parse_compat_function): Declared.

* hash.c, hash.h (tweak_hash): New function.

* lib.c (compat_fixup): Call parse_compat_fixup.

1 files changed, 7 insertions, 1 deletions

diff --git a/parser.c b/parser.c
index 0deb3867..169b58b0 100644
--- a/parser.c
+++ b/parser.c
@@ -1878,7 +1878,7 @@ void parse_init(void)
   parser_cls = cobj_register(parser_s);
 
   protect(&stream_parser_hash, &unique_s, &catch_all, convert(val *, 0));
-  stream_parser_hash = make_hash(t, nil, nil);
+  stream_parser_hash = make_hash(t, t, nil);
   catch_all = cons(t, nil);
 
   parser_l_init();
@@ -1897,3 +1897,9 @@ void parse_init(void)
   reg_fun(intern(lit("repl"), system_package), func_n4(repl));
   reg_mac(json_s, func_n2(me_json));
 }
+
+void parse_compat_fixup(int compat_ver)
+{
+  if (compat_ver <= 266)
+    tweak_hash(stream_parser_hash, t, nil);
+}