diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 72ee6edcf8d..3b559c516ed 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,16 @@
+2016-01-21  Jonathan Wakely  <jwakely@redhat.com>
+
+	PR libstdc++/69406
+	* include/bits/cpp_type_traits.h: Ensure C++ language linkage.
+	* include/ext/type_traits.h: Likewise.
+	* testsuite/17_intro/headers/c++2011/linkage.cc: Check autoconf macros
+	for presence of C headers.
+	* testsuite/ext/type_traits/add_unsigned_floating_neg.cc: Adjust
+	dg-error line number.
+	* testsuite/ext/type_traits/add_unsigned_integer_neg.cc: Likewise.
+	* testsuite/ext/type_traits/remove_unsigned_floating_neg.cc: Likewise.
+	* testsuite/ext/type_traits/remove_unsigned_integer_neg.cc: Likewise.
+
 2016-01-20  Torvald Riegel  <triegel@redhat.com>
 
 	PR libstdc++/69310
diff --git a/libstdc++-v3/include/bits/cpp_type_traits.h b/libstdc++-v3/include/bits/cpp_type_traits.h
index 3b188d4cc80..fff1e9949d0 100644
--- a/libstdc++-v3/include/bits/cpp_type_traits.h
+++ b/libstdc++-v3/include/bits/cpp_type_traits.h
@@ -64,6 +64,8 @@
 // removed.
 //
 
+extern "C++" {
+
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -408,5 +410,6 @@ __INT_N(__GLIBCXX_TYPE_INT_N_3)
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
+} // extern "C++"
 
 #endif //_CPP_TYPE_TRAITS_H
diff --git a/libstdc++-v3/include/ext/type_traits.h b/libstdc++-v3/include/ext/type_traits.h
index 0a4f4255015..dd276578969 100644
--- a/libstdc++-v3/include/ext/type_traits.h
+++ b/libstdc++-v3/include/ext/type_traits.h
@@ -34,6 +34,8 @@
 #include <bits/c++config.h>
 #include <bits/cpp_type_traits.h>
 
+extern "C++" {
+
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
@@ -214,5 +216,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
+} // extern "C++"
 
 #endif 
diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2011/linkage.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2011/linkage.cc
index 33e70535c1c..67c384b81ff 100644
--- a/libstdc++-v3/testsuite/17_intro/headers/c++2011/linkage.cc
+++ b/libstdc++-v3/testsuite/17_intro/headers/c++2011/linkage.cc
@@ -20,15 +20,23 @@
 
 // libstdc++/69386
 
+#include <bits/c++config.h>
+
 extern "C"
 {
 #include <assert.h>
+#ifdef _GLIBCXX_HAVE_COMPLEX_H
 #include <complex.h>
+#endif
 #include <ctype.h>
 #include <errno.h>
+#ifdef _GLIBCXX_HAVE_FENV_H
 #include <fenv.h>
+#endif
 #include <float.h>
+#ifdef _GLIBCXX_HAVE_INTTYPES_H
 #include <inttypes.h>
+#endif
 #include <iso646.h>
 #include <limits.h>
 #include <locale.h>
@@ -36,15 +44,27 @@ extern "C"
 #include <setjmp.h>
 #include <signal.h>
 #include <stdarg.h>
+#ifdef _GLIBCXX_HAVE_STDBOOL_H
 #include <stdbool.h>
+#endif
 #include <stddef.h>
+#ifdef _GLIBCXX_HAVE_STDINT_H
 #include <stdint.h>
+#endif
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#ifdef _GLIBCXX_HAVE_TGMATH_H
 #include <tgmath.h>
+#endif
 #include <time.h>
+#if __has_include(<uchar.h>)
 #include <uchar.h>
+#endif
+#ifdef _GLIBCXX_HAVE_WCHAR_H
 #include <wchar.h>
+#endif
+#ifdef _GLIBCXX_HAVE_WCTYPE_H
 #include <wctype.h>
+#endif
 }
diff --git a/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_floating_neg.cc b/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_floating_neg.cc
index f0c48d0c16c..09d2c7c41a4 100644
--- a/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_floating_neg.cc
+++ b/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_floating_neg.cc
@@ -35,4 +35,4 @@ int main()
 }
 
 // { dg-error "required from" "" { target *-*-* } 28 }
-// { dg-error "no type" "" { target *-*-* } 69 } 
+// { dg-error "no type" "" { target *-*-* } 71 } 
diff --git a/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_integer_neg.cc b/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_integer_neg.cc
index cee08a39a8d..567684ee958 100644
--- a/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_integer_neg.cc
+++ b/libstdc++-v3/testsuite/ext/type_traits/add_unsigned_integer_neg.cc
@@ -36,5 +36,5 @@ int main()
 }
 
 // { dg-error "invalid use of incomplete" "" { target *-*-* } 28 } 
-// { dg-error "declaration of" "" { target *-*-* } 98 }
-// { dg-error "declaration of" "" { target *-*-* } 101 }
+// { dg-error "declaration of" "" { target *-*-* } 100 }
+// { dg-error "declaration of" "" { target *-*-* } 103 }
diff --git a/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_floating_neg.cc b/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_floating_neg.cc
index 98ba8a6fdc6..c946a4f0ad6 100644
--- a/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_floating_neg.cc
+++ b/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_floating_neg.cc
@@ -35,4 +35,4 @@ int main()
 }
 
 // { dg-error "required from" "" { target *-*-* } 28 }
-// { dg-error "no type" "" { target *-*-* } 112 }
+// { dg-error "no type" "" { target *-*-* } 114 }
diff --git a/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_integer_neg.cc b/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_integer_neg.cc
index 14e671d7a90..a2cc4c768c2 100644
--- a/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_integer_neg.cc
+++ b/libstdc++-v3/testsuite/ext/type_traits/remove_unsigned_integer_neg.cc
@@ -36,5 +36,5 @@ int main()
 }
 
 // { dg-error "invalid use of incomplete" "" { target *-*-* } 28 } 
-// { dg-error "declaration of" "" { target *-*-* } 141 }
-// { dg-error "declaration of" "" { target *-*-* } 144 }
+// { dg-error "declaration of" "" { target *-*-* } 143 }
+// { dg-error "declaration of" "" { target *-*-* } 146 }