ax_prog_bison.m4

# ===========================================================================
#      https://www.gnu.org/software/autoconf-archive/ax_prog_bison.html
# ===========================================================================
#
# SYNOPSIS
#
#   AX_PROG_BISON(ACTION-IF-TRUE,ACTION-IF-FALSE)
#
# DESCRIPTION
#
#   Check whether bison is the parser generator. Run ACTION-IF-TRUE if
#   successful, ACTION-IF-FALSE otherwise
#
# LICENSE
#
#   Copyright (c) 2009 Francesco Salvestrini <salvestrini@users.sourceforge.net>
#   Copyright (c) 2010 Diego Elio Petteno` <flameeyes@gmail.com>
#
#   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 2 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 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 <https://www.gnu.org/licenses/>.
#
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#   gives unlimited permission to copy, distribute and modify the configure
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#serial 10

AC_DEFUN([AX_PROG_BISON], [
  AC_REQUIRE([AC_PROG_YACC])
  AC_REQUIRE([AC_PROG_EGREP])

  AC_CACHE_CHECK([if bison is the parser generator],[ax_cv_prog_bison],[
    AS_IF([$YACC --version 2>/dev/null | $EGREP -q '^bison '],
      [ax_cv_prog_bison=yes], [ax_cv_prog_bison=no])
  ])
  AS_IF([test "$ax_cv_prog_bison" = "yes"], [
      dnl replace the yacc-compatible compiler with the real bison, as
      dnl otherwise autoconf limits us to the POSIX yacc.
      dnl We also change the generated filename to the old one, so that
      dnl automake's ylwrap can deal with it.
      YACC="${YACC% -y} -o y.tab.c"
    ] m4_ifnblank([$1], [[$1]]),
    m4_ifnblank([$2], [[$2]])
  )
])