From 61302673d5870dc3eae32ba0e1c60d2d9f6aef21 Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Fri, 6 Feb 2015 23:20:11 -0800
Subject: * unwind.c (uw_throw): Detect invalid re-entry and bail. Cautiously,
 we use fprintf rather than our streams system, in case some problem with the
 streams is involved in this mess.

---
 unwind.c | 7 +++++++
 1 file changed, 7 insertions(+)

(limited to 'unwind.c')

diff --git a/unwind.c b/unwind.c
index 7e35c937..5d358e42 100644
--- a/unwind.c
+++ b/unwind.c
@@ -260,6 +260,12 @@ val uw_exception_subtype_p(val sub, val sup)
 val uw_throw(val sym, val args)
 {
   uw_frame_t *ex;
+  static int reentry_count = 0;
+
+  if (++reentry_count > 1) {
+    fprintf(stderr, "txr: invalid re-entry of exception handling logic\n");
+    abort();
+  }
 
   if (!listp(args))
     args = cons(args, nil);
@@ -334,6 +340,7 @@ val uw_throw(val sym, val args)
   ex->ca.sym = sym;
   ex->ca.args = args;
   uw_exit_point = ex;
+  reentry_count--;
   uw_unwind_to_exit_point();
   abort();
 }
-- 
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