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.

1 files changed, 4 insertions, 0 deletions

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)