From: Taylor R Campbell <campbell@mumble.net>
Date: Sun, 22 May 2011 21:50:50 +0000 (+0000)
Subject: Use MAKE-STRONG-EQ-HASH-TABLE for SOS's built-in class table.
X-Git-Tag: 20110609-Gtk~1^2~8
X-Git-Url: https://birchwood-abbey.net/git?a=commitdiff_plain;h=7cf2ed1b97b774689051aafe68651153a1b60d12;p=mit-scheme.git

Use MAKE-STRONG-EQ-HASH-TABLE for SOS's built-in class table.

Should be ephemeral of some flavour, but we can't do that yet.  See
the comments for details.
---

diff --git a/src/sos/class.scm b/src/sos/class.scm
index bc6946335..bd319e0d7 100644
--- a/src/sos/class.scm
+++ b/src/sos/class.scm
@@ -349,8 +349,20 @@ USA.
     class))
 
 (define built-in-class-table
-  (make-eq-hash-table))
-
+  ;; This should be an ephemeral hash table of some flavour (either
+  ;; key-ephemeral or key-and-datum-ephemeral), so that, e.g., dispatch
+  ;; tags can be garbage-collected if you redefine record types.  There
+  ;; are two reasons it is not now:
+  ;;
+  ;; 1. 9.0.1 doesn't have ephemeral hash tables, and this definition
+  ;;    figures into bootstrapping, so we can't use them here until 9.1
+  ;;    is released.
+  ;;
+  ;; 2. Methods' specializers currently hold only strong references to
+  ;;    classes anyway, which have strong references to dispatch tags,
+  ;;    so they need to be changed to hold weak references.
+  (make-strong-eq-hash-table))
+
 (let ((assign-type
        (lambda (name class)
 	 (hash-table/put! built-in-class-table