+_GL_WARN_EXTERN_C int _gl_warn_on_use
+# endif
+#endif
+
+/* _GL_WARN_ON_USE_CXX (function, rettype, parameters_and_attributes, "string")
+ is like _GL_WARN_ON_USE (function, "string"), except that the function is
+ declared with the given prototype, consisting of return type, parameters,
+ and attributes.
+ This variant is useful for overloaded functions in C++. _GL_WARN_ON_USE does
+ not work in this case. */
+#ifndef _GL_WARN_ON_USE_CXX
+# if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__)
+# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
+extern rettype function parameters_and_attributes \
+ __attribute__ ((__warning__ (msg)))
+# elif __GNUC__ >= 3 && GNULIB_STRICT_CHECKING
+/* Verify the existence of the function. */
+# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
+extern rettype function parameters_and_attributes
+# else /* Unsupported. */
+# define _GL_WARN_ON_USE_CXX(function,rettype,parameters_and_attributes,msg) \
+_GL_WARN_EXTERN_C int _gl_warn_on_use
+# endif
+#endif
+
+/* _GL_WARN_EXTERN_C declaration;
+ performs the declaration with C linkage. */
+#ifndef _GL_WARN_EXTERN_C
+# if defined __cplusplus
+# define _GL_WARN_EXTERN_C extern "C"
+# else
+# define _GL_WARN_EXTERN_C extern