From a9299da438d46958603801ed48d6fe1f637b69ee Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Sat, 16 Apr 2016 06:01:04 -0700
Subject: Block absconds across foreign frames.

* unwind.c (uw_block_abscond): If a UW_GUARD frame
occurs in the search for the abscond point, throw an error.
---
 unwind.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/unwind.c b/unwind.c
index 900d614e..a521c732 100644
--- a/unwind.c
+++ b/unwind.c
@@ -435,6 +435,10 @@ val uw_block_abscond(val tag, val result)
   for (ex = uw_stack; ex != 0; ex = ex->uw.up) {
     if (ex->uw.type == UW_BLOCK && ex->bl.tag == tag)
       break;
+    if (ex->uw.type == UW_GUARD)
+      uw_throwf(error_s, lit("~a: cannot abscond via foreign stack frames\n"),
+                prog_string, nao);
+
   }
 
   if (ex == 0)
-- 
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