Index: clang/include/clang/Driver/Options.td
===================================================================
--- clang/include/clang/Driver/Options.td
+++ clang/include/clang/Driver/Options.td
@@ -2249,7 +2249,14 @@
 def static : Flag<["-", "--"], "static">, Flags<[NoArgumentUnused]>;
 def std_default_EQ : Joined<["-"], "std-default=">;
 def std_EQ : Joined<["-", "--"], "std=">, Flags<[CC1Option]>,
-  Group<CompileOnly_Group>, HelpText<"Language standard to compile for">;
+  Group<CompileOnly_Group>, HelpText<"Language standard to compile for">,
+  ValuesCode<[{
+    const char *Values =
+    #define LANGSTANDARD(id, name, lang, desc, features) name ","
+    #define LANGSTANDARD_ALIAS(id, alias) alias ","
+    #include "clang/Frontend/LangStandards.def"
+    ;
+  }]>;
 def stdlib_EQ : Joined<["-", "--"], "stdlib=">, Flags<[CC1Option]>,
   HelpText<"C++ standard library to use">, Values<"libc++,libstdc++,platform">;
 def sub__library : JoinedOrSeparate<["-"], "sub_library">;
Index: clang/test/Driver/autocomplete.c
===================================================================
--- clang/test/Driver/autocomplete.c
+++ clang/test/Driver/autocomplete.c
@@ -95,3 +95,5 @@
 // NOWARNING: -Wno-invalid-pp-token
 // RUN: %clang --autocomplete=-analyzer-checker, | FileCheck %s -check-prefix=ANALYZER
 // ANALYZER: unix.Malloc
+// RUN: %clang --autocomplete=-std=, | FileCheck %s -check-prefix=STDVAL
+// STDVAL: c99
Index: llvm/utils/TableGen/OptParserEmitter.cpp
===================================================================
--- llvm/utils/TableGen/OptParserEmitter.cpp
+++ llvm/utils/TableGen/OptParserEmitter.cpp
@@ -303,6 +303,7 @@
   OS << "#ifdef OPTTABLE_ARG_INIT\n";
   OS << "//////////\n";
   OS << "// Option Values\n\n";
+  OS << "bool ValuesWereAdded;\n";
   for (unsigned I = 0, E = Opts.size(); I != E; ++I) {
     const Record &R = *Opts[I];
     if (!isa<UnsetInit>(R.getValueInit("ValuesCode"))) {
@@ -310,7 +311,7 @@
       OS << R.getValueAsString("ValuesCode");
       OS << "\n";
       for (const std::string &Pref : R.getValueAsListOfStrings("Prefixes")) {
-        OS << "bool ValuesWereAdded = ";
+        OS << "ValuesWereAdded = ";
         OS << "Opt.addValues(";
         std::string S = (Pref + R.getValueAsString("Name")).str();
         write_cstring(OS, S);