--- /dev/null
+/* -*- buffer-read-only: t -*- vi: set ro: */
+/* DO NOT EDIT! GENERATED AUTOMATICALLY! */
+/* A C macro for emitting warnings if a function is used.
+ Copyright (C) 2010 Free Software Foundation, Inc.
+
+ This program is free software: you can redistribute it and/or modify it
+ under the terms of the GNU General Public License as published
+ by the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+/* _GL_WARN_ON_USE(function, "literal string") issues a declaration
+ for FUNCTION which will then trigger a compiler warning containing
+ the text of "literal string" anywhere that function is called, if
+ supported by the compiler. If the compiler does not support this
+ feature, the macro expands to an unused extern declaration.
+
+ This macro is useful for marking a function as a potential
+ portability trap, with the intent that "literal string" include
+ instructions on the replacement function that should be used
+ instead. However, one of the reasons that a function is a
+ portability trap is if it has the wrong signature. Declaring
+ FUNCTION with a different signature in C is a compilation error, so
+ this macro must use the same type as any existing declaration so
+ that programs that avoid the problematic FUNCTION do not fail to
+ compile merely because they included a header that poisoned the
+ function. But this implies that _GL_WARN_ON_USE is only safe to
+ use if FUNCTION is known to already have a declaration. Use of
+ this macro implies that there must not be any other macro hiding
+ the declaration of FUNCTION; but undefining FUNCTION first is part
+ of the poisoning process anyway (although for symbols that are
+ provided only via a macro, the result is a compilation error rather
+ than a warning containing "literal string"). Also note that in
+ C++, it is only safe to use if FUNCTION has no overloads.
+
+ For an example, it is possible to poison 'getline' by:
+ - adding a call to gl_WARN_ON_USE_PREPARE([[#include <stdio.h>]],
+ [getline]) in configure.ac, which potentially defines
+ HAVE_RAW_DECL_GETLINE
+ - adding this code to a header that wraps the system <stdio.h>:
+ #undef getline
+ #if HAVE_RAW_DECL_GETLINE
+ _GL_WARN_ON_USE (getline, "getline is required by POSIX 2008, but"
+ "not universally present; use the gnulib module getline");
+ #endif
+
+ It is not possible to directly poison global variables. But it is
+ possible to write a wrapper accessor function, and poison that
+ (less common usage, like &environ, will cause a compilation error
+ rather than issue the nice warning, but the end result of informing
+ the developer about their portability problem is still achieved):
+ #if HAVE_RAW_DECL_ENVIRON
+ static inline char ***rpl_environ (void) { return &environ; }
+ _GL_WARN_ON_USE (rpl_environ, "environ is not always properly declared");
+ # undef environ
+ # define environ (*rpl_environ ())
+ #endif
+ */
+#ifndef _GL_WARN_ON_USE
+
+# if 4 < __GNUC__ || (__GNUC__ == 4 && 3 <= __GNUC_MINOR__)
+/* A compiler attribute is available in gcc versions 4.3.0 and later. */
+# define _GL_WARN_ON_USE(function, message) \
+extern __typeof__ (function) function __attribute__ ((__warning__ (message)))
+
+# else /* Unsupported. */
+# define _GL_WARN_ON_USE(function, message) \
+extern int _gl_warn_on_use
+# endif
+#endif
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