From 9cb4e7725f668318d08cb79b1459a04eadf2f925 Mon Sep 17 00:00:00 2001
From: Samuel Williams <samuel.williams@oriontransfer.co.nz>
Date: Thu, 6 Jun 2019 09:54:29 +1200
Subject: [PATCH] Handle (empty) backtrace when thread is not born yet.

---
 vm_backtrace.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/vm_backtrace.c b/vm_backtrace.c
index bb01983a7c..4f92439478 100644
--- a/vm_backtrace.c
+++ b/vm_backtrace.c
@@ -451,6 +451,12 @@ backtrace_each(const rb_execution_context_t *ec,
     const rb_control_frame_t *cfp;
     ptrdiff_t size, i;
 
+    // In the case the thread vm_stack or cfp is not initialized, there is no backtrace.
+    if (start_cfp == NULL) {
+        init(arg, 0);
+        return;
+    }
+
     /*                <- start_cfp (end control frame)
      *  top frame (dummy)
      *  top frame (dummy)