Bug #35137

* unwind.c (uw_unwind_to_exit_point): When jumping to a catch frame,
do not mark it invisible.

* unwind.h (uw_catch): Flip the matches to nil so that this catch
frame can no longer be identified as an unwind point by uw_throw,
and thus will not be re-entered for the purposes of handling
an exception. It remains visible for the purposes of running the
clean up code.
(uw_unwind): Prior to executing cleanup forms, flip the visibility
to 0. This means that the frame will no longer be re-entered
for any reason.

3 files changed, 24 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index f486688c..c7941624 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,21 @@
 2011-12-20  Kaz Kylheku  <kaz@kylheku.com>
 
+	Bug #35137
+
+	* unwind.c (uw_unwind_to_exit_point): When jumping to a catch frame,
+	do not mark it invisible.
+
+	* unwind.h (uw_catch): Flip the matches to nil so that this catch
+	frame can no longer be identified as an unwind point by uw_throw,
+	and thus will not be re-entered for the purposes of handling
+	an exception. It remains visible for the purposes of running the
+	clean up code.
+	(uw_unwind): Prior to executing cleanup forms, flip the visibility
+	to 0. This means that the frame will no longer be re-entered
+	for any reason.
+
+2011-12-20  Kaz Kylheku  <kaz@kylheku.com>
+
 	Streamlining exception handling macros a little bit.
 
 	* eval.c (op_unwind_protect): Use uw_simple_catch_begin,
diff --git a/unwind.c b/unwind.c
index 7abd4e97..03ae0104 100644
--- a/unwind.c
+++ b/unwind.c
@@ -65,11 +65,6 @@ static void uw_unwind_to_exit_point(void)
       uw_stack->ca.sym = nil;
       uw_stack->ca.exception = nil;
       uw_stack->ca.cont = uw_exit_point;
-      /* This catch frame is no longer
-         visible. If the unwind section
-         throws something, it cannot
-         be caught in the same frame. */
-      uw_stack->ca.visible = 0;
       /* 1 means unwind only. */
       longjmp(uw_stack->ca.jb, 1);
       abort();
@@ -94,10 +89,6 @@ static void uw_unwind_to_exit_point(void)
   case UW_ENV: /* env frame cannot be exit point */
     abort();
   case UW_CATCH:
-    /* Catch frame is no longer visible.
-       If a catch or unwind throw something,
-       it cannot go back to the same catch. */
-    uw_stack->ca.visible = 0;
     /* 2 means actual catch, not just unwind */
     longjmp(uw_stack->ca.jb, 2);
   default:
diff --git a/unwind.h b/unwind.h
index 98b965e7..03e43982 100644
--- a/unwind.h
+++ b/unwind.h
@@ -155,11 +155,17 @@ noreturn val type_mismatch(val, ...);
       break;                            \
     case 2:                             \
       EXCVAR = uw_catch.ca.exception;   \
-      SYMVAR = uw_catch.ca.sym;
+      SYMVAR = uw_catch.ca.sym;         \
+      /* prevent looping */             \
+      uw_catch.ca.matches = nil;
 
 #define uw_unwind                       \
+    /* suppress unused label warning */ \
+    goto uw_unwind_label;               \
     uw_unwind_label:                    \
-    case 1:
+    case 1:                             \
+      /* prevent looping */             \
+      uw_catch.ca.visible = 0;
 
 #define uw_catch_end                    \
       break;                            \