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+dnl 'extern inline' a la ISO C99.
+
+dnl Copyright 2012-2023 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+AC_DEFUN([gl_EXTERN_INLINE],
+[
+ AC_CACHE_CHECK([whether ctype.h defines __header_inline],
+ [gl_cv_have___header_inline],
+ [AC_PREPROC_IFELSE(
+ [AC_LANG_SOURCE([[#include <ctype.h>
+ #ifndef __header_inline
+ #error "<ctype.h> does not define __header_inline"
+ #endif
+ ]])],
+ [gl_cv_have___header_inline=yes],
+ [gl_cv_have___header_inline=no])])
+ if test "$gl_cv_have___header_inline" = yes; then
+ AC_DEFINE([HAVE___HEADER_INLINE], [1],
+ [Define to 1 if ctype.h defines __header_inline.])
+ fi
+
+ AH_VERBATIM([HAVE___HEADER_INLINE_1],
+[/* Please see the Gnulib manual for how to use these macros.
+
+ Suppress extern inline with HP-UX cc, as it appears to be broken; see
+ <https://lists.gnu.org/r/bug-texinfo/2013-02/msg00030.html>.
+
+ Suppress extern inline with Sun C in standards-conformance mode, as it
+ mishandles inline functions that call each other. E.g., for 'inline void f
+ (void) { } inline void g (void) { f (); }', c99 incorrectly complains
+ 'reference to static identifier "f" in extern inline function'.
+ This bug was observed with Oracle Developer Studio 12.6
+ (Sun C 5.15 SunOS_sparc 2017/05/30).
+
+ Suppress extern inline (with or without __attribute__ ((__gnu_inline__)))
+ on configurations that mistakenly use 'static inline' to implement
+ functions or macros in standard C headers like <ctype.h>. For example,
+ if isdigit is mistakenly implemented via a static inline function,
+ a program containing an extern inline function that calls isdigit
+ may not work since the C standard prohibits extern inline functions
+ from calling static functions (ISO C 99 section 6.7.4.(3).
+ This bug is known to occur on:
+
+ OS X 10.8 and earlier; see:
+ https://lists.gnu.org/r/bug-gnulib/2012-12/msg00023.html
+
+ DragonFly; see
+ http://muscles.dragonflybsd.org/bulk/clang-master-potential/20141111_102002/logs/ah-tty-0.3.12.log
+
+ FreeBSD; see:
+ https://lists.gnu.org/r/bug-gnulib/2014-07/msg00104.html
+
+ OS X 10.9 has a macro __header_inline indicating the bug is fixed for C and
+ for clang but remains for g++; see <https://trac.macports.org/ticket/41033>.
+ Assume DragonFly and FreeBSD will be similar.
+
+ GCC 4.3 and above with -std=c99 or -std=gnu99 implements ISO C99
+ inline semantics, unless -fgnu89-inline is used. It defines a macro
+ __GNUC_STDC_INLINE__ to indicate this situation or a macro
+ __GNUC_GNU_INLINE__ to indicate the opposite situation.
+ GCC 4.2 with -std=c99 or -std=gnu99 implements the GNU C inline
+ semantics but warns, unless -fgnu89-inline is used:
+ warning: C99 inline functions are not supported; using GNU89
+ warning: to disable this warning use -fgnu89-inline or the gnu_inline function attribute
+ It defines a macro __GNUC_GNU_INLINE__ to indicate this situation.
+ */
+#if (((defined __APPLE__ && defined __MACH__) \
+ || defined __DragonFly__ || defined __FreeBSD__) \
+ && (defined HAVE___HEADER_INLINE \
+ ? (defined __cplusplus && defined __GNUC_STDC_INLINE__ \
+ && ! defined __clang__) \
+ : ((! defined _DONT_USE_CTYPE_INLINE_ \
+ && (defined __GNUC__ || defined __cplusplus)) \
+ || (defined _FORTIFY_SOURCE && 0 < _FORTIFY_SOURCE \
+ && defined __GNUC__ && ! defined __cplusplus))))
+# define _GL_EXTERN_INLINE_STDHEADER_BUG
+#endif
+#if ((__GNUC__ \
+ ? (defined __GNUC_STDC_INLINE__ && __GNUC_STDC_INLINE__ \
+ && !defined __PCC__) \
+ : (199901L <= __STDC_VERSION__ \
+ && !defined __HP_cc \
+ && !defined __PGI \
+ && !(defined __SUNPRO_C && __STDC__))) \
+ && !defined _GL_EXTERN_INLINE_STDHEADER_BUG)
+# define _GL_INLINE inline
+# define _GL_EXTERN_INLINE extern inline
+# define _GL_EXTERN_INLINE_IN_USE
+#elif (2 < __GNUC__ + (7 <= __GNUC_MINOR__) && !defined __STRICT_ANSI__ \
+ && !defined __PCC__ \
+ && !defined _GL_EXTERN_INLINE_STDHEADER_BUG)
+# if defined __GNUC_GNU_INLINE__ && __GNUC_GNU_INLINE__
+ /* __gnu_inline__ suppresses a GCC 4.2 diagnostic. */
+# define _GL_INLINE extern inline __attribute__ ((__gnu_inline__))
+# else
+# define _GL_INLINE extern inline
+# endif
+# define _GL_EXTERN_INLINE extern
+# define _GL_EXTERN_INLINE_IN_USE
+#else
+# define _GL_INLINE _GL_UNUSED static
+# define _GL_EXTERN_INLINE _GL_UNUSED static
+#endif
+
+/* In GCC 4.6 (inclusive) to 5.1 (exclusive),
+ suppress bogus "no previous prototype for 'FOO'"
+ and "no previous declaration for 'FOO'" diagnostics,
+ when FOO is an inline function in the header; see
+ <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54113> and
+ <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63877>. */
+#if __GNUC__ == 4 && 6 <= __GNUC_MINOR__
+# if defined __GNUC_STDC_INLINE__ && __GNUC_STDC_INLINE__
+# define _GL_INLINE_HEADER_CONST_PRAGMA
+# else
+# define _GL_INLINE_HEADER_CONST_PRAGMA \
+ _Pragma ("GCC diagnostic ignored \"-Wsuggest-attribute=const\"")
+# endif
+# define _GL_INLINE_HEADER_BEGIN \
+ _Pragma ("GCC diagnostic push") \
+ _Pragma ("GCC diagnostic ignored \"-Wmissing-prototypes\"") \
+ _Pragma ("GCC diagnostic ignored \"-Wmissing-declarations\"") \
+ _GL_INLINE_HEADER_CONST_PRAGMA
+# define _GL_INLINE_HEADER_END \
+ _Pragma ("GCC diagnostic pop")
+#else
+# define _GL_INLINE_HEADER_BEGIN
+# define _GL_INLINE_HEADER_END
+#endif])
+])