merge revision(s) 5c7af72304d0ad33cd3f21b24a4bc44e8acd5b2c,d650b17686d49c2ce8e6a87039861154e93d4621: [Backport #18497]

	Assuming EXIT_SUCCESS equals 0 is not portable

	---
	 test/ruby/test_fiber.rb | 6 +++---
	 1 file changed, 3 insertions(+), 3 deletions(-)

	`rb_fiber_terminate` must not return [Bug #18497]

	In a forked process from a fiber, the fiber becomes the only
	fiber, `fiber_switch` does nothing as there is no other fibers,
	`rb_fiber_terminate` does not terminate the fiber.  In that case,
	reaches the end of `fiber_entry` finaly, which is declared as
	"COROUTINE" and should never return.
	---
	 cont.c                     |  3 ++-
	 eval_intern.h              |  2 +-
	 test/fiber/test_process.rb | 15 +++++++++++++++
	 test/ruby/test_fiber.rb    |  5 +++++
	 4 files changed, 23 insertions(+), 2 deletions(-)

1 files changed, 8 insertions, 3 deletions

diff --git a/test/ruby/test_fiber.rb b/test/ruby/test_fiber.rb
index e0cc59bd3c..9e994c7349 100644
--- a/test/ruby/test_fiber.rb
+++ b/test/ruby/test_fiber.rb
@@ -397,7 +397,7 @@ class TestFiber < Test::Unit::TestCase
                 Fiber.new {}.transfer
                 Fiber.new { Fiber.yield }
               end
-              exit!(0)
+              exit!(true)
             end
           }.transfer
           _, status = Process.waitpid2(xpid)
@@ -406,8 +406,13 @@ class TestFiber < Test::Unit::TestCase
       end.resume
     end
     pid, status = Process.waitpid2(pid)
-    assert_equal(0, status.exitstatus, bug5700)
-    assert_equal(false, status.signaled?, bug5700)
+    assert_not_predicate(status, :signaled?, bug5700)
+    assert_predicate(status, :success?, bug5700)
+
+    pid = Fiber.new {fork}.resume
+    pid, status = Process.waitpid2(pid)
+    assert_not_predicate(status, :signaled?)
+    assert_predicate(status, :success?)
   end
 
   def test_exit_in_fiber