shyouhei
diff --git a/‎vm_insnhelper.c
Lines changed: 4 additions & 0 deletions b/‎vm_insnhelper.c
Lines changed: 4 additions & 0 deletions
@@ -214,6 +214,10 @@ vm_check_canary(const rb_execution_context_t *ec, VALUE *sp)
     if (! LIKELY(vm_stack_canary_was_born)) {
         return; /* :FIXME: isn't it rather fatal to enter this branch?  */
     }
+    else if ((VALUE *)reg_cfp == ec->vm_stack + ec->vm_stack_size) {
+        /* This is at the very beginning of a thread. cfp does not exist. */
+        return;
+    }
     else if (! (iseq = GET_ISEQ())) {
         return;
     }
Original file line number	Diff line number	Diff line change
`@@ -214,6 +214,10 @@ vm_check_canary(const rb_execution_context_t ec, VALUE sp)`
`214`	`214`	`if (! LIKELY(vm_stack_canary_was_born)) {`
`215`	`215`	`return; /* :FIXME: isn't it rather fatal to enter this branch? */`
`216`	`216`	`}`
	`217`	`+ else if ((VALUE *)reg_cfp == ec->vm_stack + ec->vm_stack_size) {`
	`218`	`+ /* This is at the very beginning of a thread. cfp does not exist. */`
	`219`	`+ return;`
	`220`	`+ }`
`217`	`221`	`else if (! (iseq = GET_ISEQ())) {`
`218`	`222`	`return;`
`219`	`223`	`}`