2 files changed, 33 insertions, 2 deletions
diff --git a/clang/test/SemaCXX/PR10177.cpp b/clang/test/SemaCXX/PR10177.cpp
index 59630be5088..0d2e792f522 100644
--- a/clang/test/SemaCXX/PR10177.cpp
+++ b/clang/test/SemaCXX/PR10177.cpp
@@ -57,11 +57,10 @@ namespace N {
 }
 
 #else
-// expected-no-diagnostics
 
 namespace { template<typename> extern int n; }
 template<typename T> int g() { return n<int>; }
-namespace { extern template int n<int>; }
+namespace { extern template int n<int>; } // expected-error {{explicit instantiation declaration of 'n<int>' with internal linkage}}
 
 #endif
 
diff --git a/clang/test/SemaCXX/libcxx_valarray_hack.cpp b/clang/test/SemaCXX/libcxx_valarray_hack.cpp
new file mode 100644
index 00000000000..03dc5731299
--- /dev/null
+++ b/clang/test/SemaCXX/libcxx_valarray_hack.cpp
@@ -0,0 +1,32 @@
+// RUN: %clang_cc1 -fsyntax-only %s -std=c++11 -verify
+
+// This is a test for a hack in Clang that works around an issue with libc++'s
+// <valarray> implementation. The <valarray> header contains explicit
+// instantiations of functions that it declared with the internal_linkage
+// attribute, which are ill-formed by [temp.explicit]p13 (and meaningless).
+
+#ifdef BE_THE_HEADER
+
+#pragma GCC system_header
+namespace std {
+  using size_t = __SIZE_TYPE__;
+  template<typename T> struct valarray {
+    __attribute__((internal_linkage)) valarray(size_t) {}
+    __attribute__((internal_linkage)) ~valarray() {}
+  };
+
+  extern template valarray<size_t>::valarray(size_t);
+  extern template valarray<size_t>::~valarray();
+}
+
+#else
+
+#define BE_THE_HEADER
+#include "libcxx_valarray_hack.cpp"
+
+template<typename T> struct foo {
+  __attribute__((internal_linkage)) void x() {};
+};
+extern template void foo<int>::x(); // expected-error {{explicit instantiation declaration of 'x' with internal linkage}}
+
+#endif