thread.c: Thread.start with Symbol

* thread.c (thread_do_start): fix segfault at start with Symbol.
  proc created by Symbol#to_proc does not have environment unless
  using refinements.  [ruby-core:80147] [Bug #13313]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57969 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 2 insertions, 1 deletions

diff --git a/thread.c b/thread.c
index 9840880925..fffce53675 100644
--- a/thread.c
+++ b/thread.c
@@ -555,10 +555,11 @@ thread_do_start(rb_thread_t *th, VALUE args)
 {
     native_set_thread_name(th);
     if (!th->first_func) {
+	const VALUE *ep = vm_proc_ep(th->first_proc);
 	rb_proc_t *proc;
 	GetProcPtr(th->first_proc, proc);
 	th->errinfo = Qnil;
-	th->root_lep = rb_vm_ep_local_ep(vm_proc_ep(th->first_proc));
+	th->root_lep = ep ? rb_vm_ep_local_ep(ep) : NULL;
 	th->root_svar = Qfalse;
 	EXEC_EVENT_HOOK(th, RUBY_EVENT_THREAD_BEGIN, th->self, 0, 0, 0, Qundef);
 	th->value = rb_vm_invoke_proc(th, proc,