From 9471b5f964395f9b4f4f673239d4375e1910bfaa Mon Sep 17 00:00:00 2001
From: ringabout <43030857+ringabout@users.noreply.github.com>
Date: Wed, 12 Jul 2023 01:01:18 +0800
Subject: [PATCH] fixes #22256; fixes GC_disableOrc overflow (#22257)

---
 lib/system/orc.nim        | 2 +-
 tests/gc/tdisable_orc.nim | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)
 create mode 100644 tests/gc/tdisable_orc.nim

diff --git a/lib/system/orc.nim b/lib/system/orc.nim
index 1935407102..b7b98c3404 100644
--- a/lib/system/orc.nim
+++ b/lib/system/orc.nim
@@ -411,7 +411,7 @@ proc registerCycle(s: Cell; desc: PNimTypeV2) =
   if roots.d == nil: init(roots)
   add(roots, s, desc)
 
-  if roots.len >= rootsThreshold+defaultThreshold:
+  if roots.len - defaultThreshold >= rootsThreshold:
     collectCycles()
   when logOrc:
     writeCell("[added root]", s, desc)
diff --git a/tests/gc/tdisable_orc.nim b/tests/gc/tdisable_orc.nim
new file mode 100644
index 0000000000..b5f161c791
--- /dev/null
+++ b/tests/gc/tdisable_orc.nim
@@ -0,0 +1,9 @@
+discard """
+  joinable: false
+"""
+
+import std/asyncdispatch
+
+# bug #22256
+GC_disableMarkAndSweep()
+waitFor sleepAsync(1000)