From 446e0becb89688d2bf9261910e5694b4eab83d02 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Tue, 7 Feb 2006 17:18:40 +0000
Subject: [PATCH] improve continuation recycling to be insensitive to the
 latest stack-trace mark

svn: r2157
---
 src/mzscheme/src/fun.c     | 20 +++++++++++++-------
 src/mzscheme/src/schpriv.h |  2 +-
 2 files changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/mzscheme/src/fun.c b/src/mzscheme/src/fun.c
index b463b5f865..2e37fa2312 100644
--- a/src/mzscheme/src/fun.c
+++ b/src/mzscheme/src/fun.c
@@ -2942,7 +2942,7 @@ static void copy_in_mark_stack(Scheme_Thread *p, Scheme_Cont_Mark *cont_mark_sta
   }
 }
 
-static MZ_MARK_STACK_TYPE find_sharable_marks()
+static MZ_MARK_STACK_TYPE find_shareable_marks(int for_recycle)
 {
   Scheme_Thread *p = scheme_current_thread;
   long cmcount, delta = 0;
@@ -2955,8 +2955,9 @@ static MZ_MARK_STACK_TYPE find_sharable_marks()
 
     if (seg[pos].pos < MZ_CONT_MARK_POS)
       break;
-    if (SAME_OBJ(seg[pos].key, cont_key))
-      delta = 1;
+    if (SAME_OBJ(seg[pos].key, cont_key)
+	|| (for_recycle && SAME_OBJ(seg[pos].key, scheme_stack_dump_key)))
+      delta++;
     else
       delta = 0;
   }
@@ -3018,9 +3019,12 @@ internal_call_cc (int argc, Scheme_Object *argv[])
     sub_cont = NULL;
   if (sub_cont && (sub_cont->ss.cont_mark_pos == MZ_CONT_MARK_POS)) {
     /* Old cont is the same as this one, except that it may
-       have different marks --- not counting cont_key! */
-    if ((sub_cont->cont_mark_shareable == (long)sub_cont->ss.cont_mark_stack)
-	&& (find_sharable_marks() == MZ_CONT_MARK_STACK)) {
+       have different marks --- not counting cont_key or stack-trace 
+       info. (By not counting stack-trace info, we make debugging
+       info weaker. We might do a little better by checking that the
+       stack-trace info is actually the same.) */
+    if ((sub_cont->cont_mark_recycleable == (long)sub_cont->ss.cont_mark_stack)
+	&& (find_shareable_marks(1) == MZ_CONT_MARK_STACK)) {
       /* Just use this one. */
       Scheme_Object *argv2[1];
       argv2[0] = (Scheme_Object *)sub_cont;
@@ -3077,8 +3081,10 @@ internal_call_cc (int argc, Scheme_Object *argv[])
     msaved = copy_out_mark_stack(p, cont->ss.cont_mark_stack, sub_cont, &offset);
     cont->cont_mark_stack_copied = msaved;
     cont->cont_mark_offset = offset;
-    offset = find_sharable_marks();
+    offset = find_shareable_marks(0);
     cont->cont_mark_shareable = offset;
+    offset = find_shareable_marks(1);
+    cont->cont_mark_recycleable = offset;
   }
 
   /* Remember the original mark-stack segments. */
diff --git a/src/mzscheme/src/schpriv.h b/src/mzscheme/src/schpriv.h
index 623af2ac18..c9cc4a6367 100644
--- a/src/mzscheme/src/schpriv.h
+++ b/src/mzscheme/src/schpriv.h
@@ -910,7 +910,7 @@ typedef struct Scheme_Cont {
   Scheme_Cont_Mark *cont_mark_stack_copied;
   Scheme_Thread **cont_mark_stack_owner;
   Scheme_Cont_Mark **orig_mark_segments;
-  long cont_mark_shareable, cont_mark_offset;
+  long cont_mark_shareable, cont_mark_recycleable, cont_mark_offset;
   void *stack_start;
   void *o_start;
   Scheme_Config *init_config;