m4/ax_prepend_flag.m4

# ===========================================================================
#     https://www.gnu.org/software/autoconf-archive/ax_prepend_flag.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_PREPEND_FLAG(FLAG, [FLAGS-VARIABLE])
#
# DESCRIPTION
#
#   FLAG is added to the front of the FLAGS-VARIABLE shell variable, with a
#   space added in between.
#
#   If FLAGS-VARIABLE is not specified, the current language's flags (e.g.
#   CFLAGS) is used.  FLAGS-VARIABLE is not changed if it already contains
#   FLAG.  If FLAGS-VARIABLE is unset in the shell, it is set to exactly
#   FLAG.
#
#   NOTE: Implementation based on AX_APPEND_FLAG.
#
# LICENSE
#
#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
#   Copyright (c) 2018 John Zaitseff <J.Zaitseff@zap.org.au>
#
#   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_PREPEND_FLAG],
[dnl
AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_SET_IF
AS_VAR_PUSHDEF([FLAGS], [m4_default($2,_AC_LANG_PREFIX[FLAGS])])
AS_VAR_SET_IF(FLAGS,[
  AS_CASE([" AS_VAR_GET(FLAGS) "],
    [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
    [
     FLAGS="$1 $FLAGS"
     AC_RUN_LOG([: FLAGS="$FLAGS"])
    ])
  ],
  [
  AS_VAR_SET(FLAGS,[$1])
  AC_RUN_LOG([: FLAGS="$FLAGS"])
  ])
AS_VAR_POPDEF([FLAGS])dnl
])dnl AX_PREPEND_FLAG