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(-)

    note that only backported a part of above patch because of incompatibility
    of ruby_2_7.

1 files changed, 2 insertions, 1 deletions

diff --git a/cont.c b/cont.c
index 7f971a9e9d..f1edd82bf0 100644
--- a/cont.c
+++ b/cont.c
@@ -1796,7 +1796,7 @@ rb_fiber_new(rb_block_call_func_t func, VALUE obj)
     return fiber_initialize(fiber_alloc(rb_cFiber), rb_proc_new(func, obj), &shared_fiber_pool);
 }
 
-static void rb_fiber_terminate(rb_fiber_t *fiber, int need_interrupt);
+NORETURN(static void rb_fiber_terminate(rb_fiber_t *fiber, int need_interrupt));
 
 #define PASS_KW_SPLAT (rb_empty_keyword_given_p() ? RB_PASS_EMPTY_KEYWORDS : rb_keyword_given_p())
 
@@ -2090,6 +2090,7 @@ rb_fiber_terminate(rb_fiber_t *fiber, int need_interrupt)
     next_fiber = return_fiber();
     if (need_interrupt) RUBY_VM_SET_INTERRUPT(&next_fiber->cont.saved_ec);
     fiber_switch(next_fiber, 1, &value, 0, RB_NO_KEYWORDS);
+    ruby_stop(0);
 }
 
 VALUE