From 4f1c1c16da02071007c9d3c7eb4d577ad2502e61 Mon Sep 17 00:00:00 2001
From: dearblue <dearblue@users.osdn.me>
Date: Mon, 4 Dec 2023 22:20:44 +0900
Subject: [PATCH] Check fiber backward when switching with `Fiber#transfer`

Previously, if the caller of `Fiber#resume` had a C function call, an inconsistency would occur.
---
 mrbgems/mruby-fiber/src/fiber.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/mrbgems/mruby-fiber/src/fiber.c b/mrbgems/mruby-fiber/src/fiber.c
index f5254a286..9dc151096 100644
--- a/mrbgems/mruby-fiber/src/fiber.c
+++ b/mrbgems/mruby-fiber/src/fiber.c
@@ -167,6 +167,17 @@ fiber_check_cfunc(mrb_state *mrb, struct mrb_context *c)
   }
 }
 
+static void
+fiber_check_cfunc_recursive(mrb_state *mrb, struct mrb_context *c)
+{
+  for (;; c = c->prev) {
+    fiber_check_cfunc(mrb, c);
+    if (c == mrb->root_c || !c->prev) {
+      break;
+    }
+  }
+}
+
 static void
 fiber_switch_context(mrb_state *mrb, struct mrb_context *c)
 {
@@ -370,7 +381,7 @@ fiber_transfer(mrb_state *mrb, mrb_value self)
   const mrb_value* a;
   mrb_int len;
 
-  fiber_check_cfunc(mrb, mrb->c);
+  fiber_check_cfunc_recursive(mrb, mrb->c);
   mrb_get_args(mrb, "*!", &a, &len);
 
   if (c->status == MRB_FIBER_RESUMED) {