Index: lldb/test/Shell/Driver/TestError.test
===================================================================
--- /dev/null
+++ lldb/test/Shell/Driver/TestError.test
@@ -0,0 +1,2 @@
+RUN: not %lldb --arch 2>&1 | FileCheck %s --check-prefix ARGMISSING
+ARGMISSING: error: argument to '--arch' is missing
Index: lldb/tools/driver/Driver.cpp
===================================================================
--- lldb/tools/driver/Driver.cpp
+++ lldb/tools/driver/Driver.cpp
@@ -853,10 +853,11 @@
 
   // Parse arguments.
   LLDBOptTable T;
-  unsigned MAI;
-  unsigned MAC;
+  unsigned MissingArgIndex;
+  unsigned MissingArgCount;
   ArrayRef<const char *> arg_arr = makeArrayRef(argv + 1, argc - 1);
-  opt::InputArgList input_args = T.ParseArgs(arg_arr, MAI, MAC);
+  opt::InputArgList input_args =
+      T.ParseArgs(arg_arr, MissingArgIndex, MissingArgCount);
   llvm::StringRef argv0 = llvm::sys::path::filename(argv[0]);
 
   if (input_args.hasArg(OPT_help)) {
@@ -864,6 +865,16 @@
     return 0;
   }
 
+  // Check for missing argument error.
+  if (MissingArgCount) {
+    WithColor::error() << "argument to '"
+                       << input_args.getArgString(MissingArgIndex)
+                       << "' is missing\n";
+    llvm::errs() << "Use '" << argv0
+                 << " --help' for a complete list of options.\n";
+    return 1;
+  }
+
   // Error out on unknown options.
   if (input_args.hasArg(OPT_UNKNOWN)) {
     for (auto *arg : input_args.filtered(OPT_UNKNOWN)) {