# https://lists.gnu.org/archive/html/autoconf-commit/2012-12/msg00004.html
# AC_C__GENERIC
# -------------
# Define HAVE_C__GENERIC if _Generic works, a la C11.
AN_IDENTIFIER([_Generic], [AC_C__GENERIC])
AC_DEFUN([AC_C__GENERIC],
[AC_CACHE_CHECK([for _Generic], ac_cv_c__Generic,
[AC_COMPILE_IFELSE(
   [AC_LANG_SOURCE(
      [[int
        main (int argc, char **argv)
        {
          int a = _Generic (argc, int: argc = 1);
          int *b = &_Generic (argc, default: argc);
          char ***c = _Generic (argv, int: argc, default: argv ? &argv : 0);
          _Generic (1 ? 0 : b, int: a, default: b) = &argc;
          _Generic (a = 1, default: a) = 3;
          return a + !b + !c;
        }
      ]])],
   [ac_cv_c__Generic=yes],
   [ac_cv_c__Generic=no])])
if test $ac_cv_c__Generic = yes; then
  AC_DEFINE([HAVE_C__GENERIC], 1,
           [Define to 1 if C11-style _Generic works.])
fi
])# AC_C__GENERIC