From dd536fd567b2ba9bed67a0094c5cd905c774f951 Mon Sep 17 00:00:00 2001
From: Josh Haberman <jhaberman@gmail.com>
Date: Wed, 5 Jul 2017 15:12:59 -0700
Subject: [PATCH] Be more picky about command-line args in upbc.

---
 tools/upbc.lua | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/tools/upbc.lua b/tools/upbc.lua
index bf9a68d36a..9d9531c00c 100644
--- a/tools/upbc.lua
+++ b/tools/upbc.lua
@@ -15,8 +15,13 @@ local upb = require "upb"
 local generate_upbdefs = false
 
 for _, argument in ipairs(arg) do
-  if argument == "--generate-upbdefs" then
-    generate_upbdefs = true
+  if argument.sub(argument, 1, 2) == "--" then
+    if argument == "--generate-upbdefs" then
+      generate_upbdefs = true
+    else
+      print("Unknown flag: " .. argument)
+      return 1
+    end
   else
     src = argument
   end