fiber: fix machine stack marking when FIBER_USE_NATIVE is 0

* cont.c (cont_mark): mark Fiber machine stack correctly when
  FIBER_USE_NATIVE is 0
* test/ruby/test_fiber.rb (test_mark_fiber): new test
  [Bug #13875] [ruby-core:82681]

This bug appears to be introduced with r59557.
("refactoring Fiber status")

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59785 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 1 insertions, 1 deletions

diff --git a/cont.c b/cont.c
index f49ed2bde5..c89f7404f6 100644
--- a/cont.c
+++ b/cont.c
@@ -248,7 +248,7 @@ cont_mark(void *ptr)
 	    const rb_thread_t *th = rb_thread_ptr(cont->saved_thread.self);
 	    const rb_fiber_t *fib = (rb_fiber_t*)cont;
 
-	    if ((th->ec.fiber != fib) && FIBER_SUSPENDED_P(fib)) {
+	    if ((th->ec.fiber != fib) && !FIBER_TERMINATED_P(fib)) {
 		rb_gc_mark_locations(cont->machine.stack,
 				     cont->machine.stack + cont->machine.stack_size);
 	    }