From 13f4923551bd270404affee07a39020a83e41d57 Mon Sep 17 00:00:00 2001
From: normal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>
Date: Thu, 30 Aug 2018 19:14:37 +0000
Subject: cont.c (rb_fiber_atfork): th->root_fiber may not exist

Otherwise, bootstraptest/test_fork.rb fails with -DVM_CHECK_MODE=2

[Bug #15041]

Fixes: r64589 "cont.c: set th->root_fiber to current fiber at fork"

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@64593 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
---
 cont.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

(limited to 'cont.c')

diff --git a/cont.c b/cont.c
index 3f0a5cb45f..7bc1724176 100644
--- a/cont.c
+++ b/cont.c
@@ -1981,11 +1981,13 @@ fiber_to_s(VALUE fibval)
 void
 rb_fiber_atfork(rb_thread_t *th)
 {
-    if (&th->root_fiber->cont.saved_ec != th->ec) {
-        th->root_fiber = th->ec->fiber_ptr;
-        th->root_fiber->cont.type = ROOT_FIBER_CONTEXT;
+    if (th->root_fiber) {
+        if (&th->root_fiber->cont.saved_ec != th->ec) {
+            th->root_fiber = th->ec->fiber_ptr;
+            th->root_fiber->cont.type = ROOT_FIBER_CONTEXT;
+        }
+        th->root_fiber->prev = 0;
     }
-    th->root_fiber->prev = 0;
 }
 #endif
 
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