From d062212ebc3142864a68d94cded2fbeffcf15597 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 4 Aug 2017 10:13:52 -0600
Subject: [PATCH] future: fix problem related to continuation marks

Capturing, restoring, then capturing again a future's continuation
marks did not work right.
---
 racket/src/racket/src/fun.c    |  2 +-
 racket/src/racket/src/future.c |  3 ++-
 racket/src/racket/src/jit.c    | 12 +++---------
 3 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/racket/src/racket/src/fun.c b/racket/src/racket/src/fun.c
index b8e6e9130c..2ecc783a79 100644
--- a/racket/src/racket/src/fun.c
+++ b/racket/src/racket/src/fun.c
@@ -9025,7 +9025,7 @@ Scheme_Lightweight_Continuation *scheme_capture_lightweight_continuation(Scheme_
     seg = p->cont_mark_stack_segments[i >> SCHEME_LOG_MARK_SEGMENT_SIZE];
     pos = i & SCHEME_MARK_SEGMENT_MASK;
     
-    memcpy(cont_mark_stack_slice + i, seg + pos, sizeof(Scheme_Cont_Mark));
+    memcpy(cont_mark_stack_slice + j, seg + pos, sizeof(Scheme_Cont_Mark));
   }
 
   return lw;
diff --git a/racket/src/racket/src/future.c b/racket/src/racket/src/future.c
index cf328b9050..0daf222ea8 100644
--- a/racket/src/racket/src/future.c
+++ b/racket/src/racket/src/future.c
@@ -2369,6 +2369,8 @@ void *worker_thread_future_loop(void *arg)
           Scheme_Object *rator, **argv;
           int argc;
 
+          scheme_fill_lwc_start();
+
           if (ft->suspended_lw_stack) {
             Scheme_Lightweight_Continuation *lc;
 
@@ -2387,7 +2389,6 @@ void *worker_thread_future_loop(void *arg)
             argv = NULL;
           }
 
-          scheme_fill_lwc_start();
           jitcode = ((Scheme_Native_Closure *)rator)->code->start_code;
           v = scheme_call_as_lightweight_continuation(jitcode, rator, argc, argv);
           if (SAME_OBJ(v, SCHEME_TAIL_CALL_WAITING))
diff --git a/racket/src/racket/src/jit.c b/racket/src/racket/src/jit.c
index 2eae1f3ac6..860b13072a 100644
--- a/racket/src/racket/src/jit.c
+++ b/racket/src/racket/src/jit.c
@@ -132,16 +132,13 @@ THREAD_LOCAL_DECL(Scheme_Current_LWC *scheme_current_lwc);
 static Scheme_Object *do_call_as_lwc(Scheme_Native_Proc *code,
                                      void *data,
                                      int argc,
-                                     Scheme_Object **argv,
-                                     MZ_MARK_STACK_TYPE cont_mark_stack_start)
+                                     Scheme_Object **argv)
 {
 #ifdef JIT_THREAD_LOCAL
 # define THDLOC &BOTTOM_VARIABLE
 #else
 # define THDLOC NULL
 #endif
-  scheme_current_lwc->runstack_start = MZ_RUNSTACK;
-  scheme_current_lwc->cont_mark_stack_start = cont_mark_stack_start;
   return sjc.native_starter_code(data, argc, argv, THDLOC, code, (void **)&scheme_current_lwc->stack_start);
 #undef THDLOC
 }
@@ -151,16 +148,13 @@ Scheme_Object *scheme_call_as_lightweight_continuation(Scheme_Native_Proc *code,
                                                        int argc,
                                                        Scheme_Object **argv)
 {
-  return do_call_as_lwc(code, data, argc, argv, MZ_CONT_MARK_STACK);
+  return do_call_as_lwc(code, data, argc, argv);
 }
 
 #ifdef MZ_USE_FUTURES
 Scheme_Object *scheme_force_value_same_mark_as_lightweight_continuation(Scheme_Object *v)
 {
-  /* Providing 0 as cont_mark_stack_start is the "same_mark" part:
-     it preserves any continuation marks that are in place as part
-     of the continuation. */
-  return do_call_as_lwc(sjc.force_value_same_mark_code, NULL, 0, NULL, 0);
+  return do_call_as_lwc(sjc.force_value_same_mark_code, NULL, 0, NULL);
 }
 #endif