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dnl Copyright (C) 2000, 2006 Free Software Foundation, Inc.
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dnl This file is free software; the Free Software Foundation
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dnl gives unlimited permission to copy and/or distribute it,
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dnl with or without modifications, as long as this notice is preserved.
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# Check for GNU m4, at least 1.3 (supports frozen files).
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# Also, check whether --error-output (through 1.4.x) or --debugfile (2.0)
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# is supported, and AC_SUBST M4_DEBUGFILE accordingly.
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AC_DEFUN([AC_PROG_GNU_M4],
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[AC_PATH_PROGS([M4], [gm4 gnum4 m4], [m4])
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AC_CACHE_CHECK([whether m4 supports frozen files], [ac_cv_prog_gnu_m4],
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if test x"$M4" != x; then
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case `$M4 --help < /dev/null 2>&1` in
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*reload-state*) ac_cv_prog_gnu_m4=yes ;;
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if test $ac_cv_prog_gnu_m4 = yes ; then
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AC_CACHE_CHECK([how m4 supports trace files], [ac_cv_prog_gnu_m4_debugfile],
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[case `$M4 --help < /dev/null 2>&1` in
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*debugfile*) ac_cv_prog_gnu_m4_debugfile=--debugfile ;;
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*) ac_cv_prog_gnu_m4_debugfile=--error-output ;;
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AC_SUBST([M4_DEBUGFILE], $ac_cv_prog_gnu_m4_debugfile)