# m4.m4 serial 5
dnl Copyright (C) 2000, 2006, 2007, 2008 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_PROG_GNU_M4
# --------------
# Check for GNU M4, at least 1.4.5 (all earlier versions had a bug in
# trace support:
# http://lists.gnu.org/archive/html/bug-gnu-utils/2006-11/msg00096.html)
# Also, check whether --error-output (through 1.4.x) or --debugfile (2.0)
# is supported, and AC_SUBST M4_DEBUGFILE accordingly.
AC_DEFUN([AC_PROG_GNU_M4],
  [AC_ARG_VAR([M4], [Location of GNU M4 1.4.5 or later.  Defaults to the first
    program of `m4', `gm4', or `gnum4' on PATH that meets Autoconf needs.])
  AC_CACHE_CHECK([for GNU M4 that supports accurate traces], [ac_cv_path_M4],
    [rm -f conftest.m4f
AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4 gnum4],
      [dnl Creative quoting here to avoid raw dnl and ifdef in configure.
      # Root out GNU M4 1.4.4, as well as non-GNU m4 that ignore -t, -F.
      ac_snippet=change'quote(<,>)in''dir(<if''def>,mac,bug)d'nl
      test -z "`$ac_path_M4 -F conftest.m4f </dev/null 2>&1`" \
      && test -z "`echo $ac_snippet | $ac_path_M4 --trace=mac 2>&1`" \
      && test -f conftest.m4f \
      && ac_cv_path_M4=$ac_path_M4 ac_path_M4_found=:
      rm -f conftest.m4f],
      [AC_MSG_ERROR([no acceptable m4 could be found in \$PATH.
GNU M4 1.4.5 or later is required; 1.4.11 is recommended])])])
  M4=$ac_cv_path_M4
  AC_CACHE_CHECK([how m4 supports trace files], [ac_cv_prog_gnu_m4_debugfile],
    [case `$M4 --help < /dev/null 2>&1` in
      *debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
      *) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
    esac])
  AC_SUBST([M4_DEBUGFILE], [$ac_cv_prog_gnu_m4_debugfile])
])

# Compatibility for bootstrapping with Autoconf 2.61.
dnl FIXME - replace this with AC_PREREQ([2.62]) after the release.
# AC_PATH_PROGS_FEATURE_CHECK was added the same time the slightly broken,
# undocumented _AC_PATH_PROG_FEATURE_CHECK was deleted.
m4_ifndef([AC_PATH_PROGS_FEATURE_CHECK],
  [m4_define([AC_PATH_PROGS_FEATURE_CHECK],
    [_AC_PATH_PROG_FEATURE_CHECK([$1], [$2], [$3], [$5])
])])