Index: lib/AST/Decl.cpp
===================================================================
--- lib/AST/Decl.cpp
+++ lib/AST/Decl.cpp
@@ -2732,6 +2732,12 @@
   if (getStorageClass() == SC_Static)
     return 0;

+  // According to OpenCL v1.2 s6.9.f, the library functions defined in
+  // the C99 standard headers are not available.
+  if (Context.getLangOpts().OpenCL &&
+      Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
+    return 0;
+
   return BuiltinID;
 }

Index: test/SemaOpenCL/printf.cl
===================================================================
--- /dev/null
+++ test/SemaOpenCL/printf.cl
@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 %s -verify -pedantic -fsyntax-only
+// expected-no-diagnostics
+
+typedef float float4 __attribute__((ext_vector_type(4)));
+int printf(__constant const char* st, ...);
+
+void test(void)
+{
+  float4 a;
+  printf("%8.4v4hlf\n", a);
+}