Avoid assertion violation when comparing with main-thread

* src/thread.c (unmark_main_thread): New function.
* src/lisp.h (unmark_main_thread): Prototype it.
* src/alloc.c (garbage_collect_1): Call it after sweeping.
(Bug#33073)

* test/src/thread-tests.el (threads-test-bug33073): New test.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/thread.c b/src/thread.c
index 0cd1ae33dc2..47f55e7f67c 100644
--- a/src/thread.c
+++ b/src/thread.c
@@ -656,6 +656,12 @@ mark_threads (void)
   flush_stack_call_func (mark_threads_callback, NULL);
 }
 
+void
+unmark_main_thread (void)
+{
+  main_thread.header.size &= ~ARRAY_MARK_FLAG;
+}
+
 
 
 static void