From 3df89b1573d415bb18a912c4c774edc189b1ac11 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sun, 15 May 2016 22:59:38 -0700
Subject: Some streamlining in the cons recycling.

* lib.c (rcyc_pop): Just assume that *plist points to a cons
and access the fields directly.
(rcyc_cons): Don't bother with rplacd.
(rcyc_list): Don't bother with set macro.

* regex.c (read_until_match): Defensive coding: locally
ensure that rcyc_pop won't be called on a nil stack,
which will now segfault.
---
 lib.c   | 18 ++++++++----------
 regex.c |  2 +-
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/lib.c b/lib.c
index 64a22b68..4b158752 100644
--- a/lib.c
+++ b/lib.c
@@ -605,8 +605,8 @@ val pop(val *plist)
 val rcyc_pop(val *plist)
 {
   val rcyc = *plist;
-  val ret = car(rcyc);
-  *plist = cdr(rcyc);
+  val ret = rcyc->c.car;
+  *plist = rcyc->c.cdr;
   rcyc_cons(rcyc);
   return ret;
 }
@@ -2535,7 +2535,7 @@ val make_half_lazy_cons(val func, val car)
 
 void rcyc_cons(val cons)
 {
-  rplacd(cons, recycled_conses);
+  cons->c.cdr = recycled_conses;
   cons->c.car = nil;
   recycled_conses = cons;
 }
@@ -2545,13 +2545,11 @@ void rcyc_list(val list)
   if (list) {
     val rl_orig = recycled_conses;
     recycled_conses = list;
-    for (; list; list = list->c.cdr) {
-      list->c.car = nil;
-      if (!list->c.cdr) {
-        set(mkloc(list->lc.cdr, list), rl_orig);
-        break;
-      }
-    }
+
+    while (list->c.cdr)
+      list = list->c.cdr;
+
+    list->c.cdr = rl_orig;
   }
 }
 
diff --git a/regex.c b/regex.c
index faf38965..4ad34dcf 100644
--- a/regex.c
+++ b/regex.c
@@ -2579,7 +2579,7 @@ val read_until_match(val regex, val stream_in, val include_match_in)
 
   if (nil) {
 out_match:
-    while (stack != match)
+    while (stack && stack != match)
       unget_char(rcyc_pop(&stack), stream);
     if (!out)
       out = null_string;
-- 
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