New :postfini feature in defstruct.

The :postfini clause registers a finalizer that runs in the
ordinary order: after previously registered ones. This has
the effect of allowing a derived structure to run clean-up
actions after those of inherited structures. Either order
can be useful because the dependencies between base and
derived can go in either direction. It's a huge mistake in
C++ that it supports only derived-first destructor invocation
order.

* stdlib/struct.tl (defstruct): Recognize and translate
:postfini clause. It's exactly like :fini but omits the
t parameter in the finalize call, registering in the
natural order.

* tests/012/fini.tl (derived): Add :postfini handler.

* tests/012/fini.expected: Updated to reflect the messages
coming from the postfini handler, which are happening
in the correct order.

* txr.1: Documented.

2 files changed, 43 insertions, 1 deletions

diff --git a/tests/012/fini.expected b/tests/012/fini.expected
index 5e967eb2..a733802b 100644
--- a/tests/012/fini.expected
+++ b/tests/012/fini.expected
@@ -2,44 +2,64 @@ inside with-objects
 base:21 finalized
 derived:1 derived fini
 derived:1 finalized
+derived:1 derived postfini
 derived:2 derived fini
 derived:2 finalized
+derived:2 derived postfini
 derived:3 derived fini
 derived:3 finalized
+derived:3 derived postfini
 derived:4 derived fini
 derived:4 finalized
+derived:4 derived postfini
 derived:5 derived fini
 derived:5 finalized
+derived:5 derived postfini
 derived:6 derived fini
 derived:6 finalized
+derived:6 derived postfini
 derived:7 derived fini
 derived:7 finalized
+derived:7 derived postfini
 derived:8 derived fini
 derived:8 finalized
+derived:8 derived postfini
 derived:9 derived fini
 derived:9 finalized
+derived:9 derived postfini
 derived:10 derived fini
 derived:10 finalized
+derived:10 derived postfini
 derived:11 derived fini
 derived:11 finalized
+derived:11 derived postfini
 derived:12 derived fini
 derived:12 finalized
+derived:12 derived postfini
 derived:13 derived fini
 derived:13 finalized
+derived:13 derived postfini
 derived:14 derived fini
 derived:14 finalized
+derived:14 derived postfini
 derived:15 derived fini
 derived:15 finalized
+derived:15 derived postfini
 derived:16 derived fini
 derived:16 finalized
+derived:16 derived postfini
 derived:17 derived fini
 derived:17 finalized
+derived:17 derived postfini
 derived:18 derived fini
 derived:18 finalized
+derived:18 derived postfini
 derived:19 derived fini
 derived:19 finalized
+derived:19 derived postfini
 derived:20 derived fini
 derived:20 finalized
+derived:20 derived postfini
 after with-objects
 derived:41 derived fini
 derived:41 finalized
@@ -81,3 +101,23 @@ derived:23 derived fini
 derived:23 finalized
 derived:22 derived fini
 derived:22 finalized
+derived:22 derived postfini
+derived:23 derived postfini
+derived:24 derived postfini
+derived:25 derived postfini
+derived:26 derived postfini
+derived:27 derived postfini
+derived:28 derived postfini
+derived:29 derived postfini
+derived:30 derived postfini
+derived:31 derived postfini
+derived:32 derived postfini
+derived:33 derived postfini
+derived:34 derived postfini
+derived:35 derived postfini
+derived:36 derived postfini
+derived:37 derived postfini
+derived:38 derived postfini
+derived:39 derived postfini
+derived:40 derived postfini
+derived:41 derived postfini
diff --git a/tests/012/fini.tl b/tests/012/fini.tl
index 3aa581f9..775f210f 100644
--- a/tests/012/fini.tl
+++ b/tests/012/fini.tl
@@ -11,7 +11,9 @@
 
 (defstruct derived base
   (:fini (me)
-    (put-line `@(typeof me):@{me.id} derived fini`)))
+    (put-line `@(typeof me):@{me.id} derived fini`))
+  (:postfini (me)
+    (put-line `@(typeof me):@{me.id} derived postfini`)))
 
 (unwind-protect
   (with-objects ((b (new base others (mapcar (ret (new derived)) (range 1 20)))))