# m4.m4 serial 12

# Copyright (C) 2000, 2006-2019, 2021-2022 Free Software Foundation,
# Inc.

# 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 warranty of any kind.

# AC_PROG_GNU_M4
# --------------
# Check for GNU M4, at least 1.4.6 (all earlier versions had bugs in
# trace support and regexp support):
# http://lists.gnu.org/archive/html/bug-gnu-utils/2006-11/msg00096.html
# http://lists.gnu.org/archive/html/bug-autoconf/2009-07/msg00023.html
# Also, check whether --error-output (through 1.4.x) or --debugfile (2.0)
# is supported, and AC_SUBST M4_DEBUGFILE accordingly.
# Also avoid versions of m4 that trigger strstr bugs.
AC_DEFUN([AC_PROG_GNU_M4],
  [AC_ARG_VAR([M4], [Location of GNU M4 1.4.6 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_had_posixly_correct=${POSIXLY_CORRECT:+yes}
AS_UNSET([POSIXLY_CORRECT])
AC_PATH_PROGS_FEATURE_CHECK([M4], [m4 gm4 gnum4],
      [dnl Creative quoting here to avoid raw dnl and ifdef in configure.
      # Root out GNU M4 1.4.5, as well as non-GNU m4 that ignore -t, -F.
      # Root out GNU M4 1.4.15 with buggy false negative replacement strstr.
      # Root out Glibc 2.9 - 2.12 and GNU M4 1.4.11 - 1.4.15 with buggy
      # false positive strstr.
      ac_snippet=change'quote(<,>)in''dir(<if''def>,mac,bug)'
      ac_snippet=${ac_snippet}pat'subst(a,\(b\)\|\(a\),\1)d'nl
      ac_snippet=$ac_snippet${as_nl}if'else(in''dex(..wi.d.,.d.),-1,bug)'
      ac_snippet=$ac_snippet${as_nl}if'else(in''dex(dnl
;:11-:12-:12-:12-:12-:12-:12-:12-:12.:12.:12.:12.:12.:12.:12.:12.:12-,dnl
:12-:12-:12-:12-:12-:12-:12-:12-),-1,,strstr-bug2)'
      test -z "`$ac_path_M4 -F conftest.m4f </dev/null 2>&1`" \
      && test -z "`AS_ECHO([$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 1.4.6 or later is required; 1.4.16 or newer is recommended.
GNU M4 1.4.15 uses a buggy replacement strstr on some systems.
Glibc 2.9 - 2.12 and GNU M4 1.4.11 - 1.4.15 have another strstr bug.])])])
  M4=$ac_cv_path_M4
  AC_CACHE_CHECK([whether $ac_cv_path_M4 accepts --gnu],
    [ac_cv_prog_gnu_m4_gnu],
    [case `$M4 --help < /dev/null 2>&1` in
      *--gnu*) ac_cv_prog_gnu_m4_gnu=yes ;;
      *) ac_cv_prog_gnu_m4_gnu=no ;;
    esac])
  if test yes = "$ac_cv_prog_gnu_m4_gnu"; then
    M4_GNU=--gnu
  else
    M4_GNU=
  fi
  AC_SUBST([M4_GNU])
  if test yes = "$ac_had_posixly_correct"; then
    POSIXLY_CORRECT=:
    if test no = $ac_cv_prog_gnu_m4_gnu; then
      AC_MSG_WARN([the version of M4 that was found does not support -g])
      AC_MSG_WARN([using it with POSIXLY_CORRECT set may cause problems])
    fi
  fi
  AC_CACHE_CHECK([how m4 supports trace files], [ac_cv_prog_gnu_m4_debugfile],
    [case `$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])
])])
