From b298e241c82b72a84b6f852e435b0f2f38cfbb42 Mon Sep 17 00:00:00 2001
From: "Yukihiro \"Matz\" Matsumoto" <matz@ruby-lang.org>
Date: Thu, 15 Jun 2017 14:54:29 +0900
Subject: Protect the last exception object from GC in `ecall`; fix #3702

---
 src/vm.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/vm.c b/src/vm.c
index 419b93be1..e3460d742 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -302,6 +302,7 @@ ecall(mrb_state *mrb, int i)
   mrb_value *self = mrb->c->stack;
   struct RObject *exc;
   ptrdiff_t cioff;
+  int ai = mrb_gc_arena_save(mrb);
 
   if (i<0) return;
   if (ci - mrb->c->cibase > MRB_FUNCALL_DEPTH_MAX) {
@@ -321,9 +322,13 @@ ecall(mrb_state *mrb, int i)
   ci->target_class = p->target_class;
   mrb->c->stack = mrb->c->stack + ci[-1].nregs;
   exc = mrb->exc; mrb->exc = 0;
+  if (exc) {
+    mrb_gc_protect(mrb, mrb_obj_value(exc));
+  }
   mrb_run(mrb, p, *self);
   mrb->c->ci = mrb->c->cibase + cioff;
   if (!mrb->exc) mrb->exc = exc;
+  mrb_gc_arena_restore(mrb, ai);
 }
 
 #ifndef MRB_FUNCALL_ARGC_MAX
-- 
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