how to properly initialize builtins for RecursiveASTVisitor

I’ve added the AddPath()'s for my system headers, but now get errors like:

…/bin/…/lib/clang/3.3/include/stdarg.h:30:9: error: unknown type name ‘__builtin_va_list’; did you mean '__builti
…/osse/core/inc/ossmath.h:48:11: error: use of undeclared identifier ‘__builtin_sqrt’; did you mean '_builtin

I’m guessing this is due to how I’m initializing the builtin context:

Builtin::Context builtinContext ;

builtinContext.InitializeTarget( *pTargetInfo ) ;

ASTContext * pASTcontext = new ASTContext( languageOptions,
sourceManager,
pTargetInfo,
identifierTable,
selectorTable,
builtinContext,
0 /* size_reserve*/ ) ;

I tried adding:

builtinContext.InitializeBuiltins( identifierTable, languageOptions ) ;

before the ASTContext creation, but this doesn’t appear to have an effect? My Langopts now include:

languageOptions.GNUMode = 1 ;
languageOptions.CXXExceptions = 1 ;
languageOptions.RTTI = 1 ;
languageOptions.Bool = 1 ;
languageOptions.CPlusPlus = 1 ;
languageOptions.WChar = 1 ;

and I see that NoBuiltin is already 0 by default?