# ===========================================================================#    https://www.gnu.org/software/autoconf-archive/ax_require_defined.html# ===========================================================================## SYNOPSIS##   AX_REQUIRE_DEFINED(MACRO)## DESCRIPTION##   AX_REQUIRE_DEFINED is a simple helper for making sure other macros have#   been defined and thus are available for use.  This avoids random issues#   where a macro isn't expanded.  Instead the configure script emits a#   non-fatal:##     ./configure: line 1673: AX_CFLAGS_WARN_ALL: command not found##   It's like AC_REQUIRE except it doesn't expand the required macro.##   Here's an example:##     AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])## LICENSE##   Copyright (c) 2014 Mike Frysinger <vapier@gentoo.org>##   Copying and distribution of this file, with or without modification, are#   permitted in any medium without royalty provided the copyright notice#   and this notice are preserved. This file is offered as-is, without any#   warranty. #serial 2 AC_DEFUN([AX_REQUIRE_DEFINED], [dnl  m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])])])dnl AX_REQUIRE_DEFINED