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1 # mmap-anon.m4 serial 8
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2 dnl Copyright (C) 2005, 2007, 2009-2010 Free Software Foundation, Inc.
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3 dnl This file is free software; the Free Software Foundation
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4 dnl gives unlimited permission to copy and/or distribute it,
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5 dnl with or without modifications, as long as this notice is preserved.
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6
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7 # Detect how mmap can be used to create anonymous (not file-backed) memory
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8 # mappings.
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9 # - On Linux, AIX, OSF/1, Solaris, Cygwin, Interix, Haiku, both MAP_ANONYMOUS
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10 # and MAP_ANON exist and have the same value.
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11 # - On HP-UX, only MAP_ANONYMOUS exists.
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12 # - On MacOS X, FreeBSD, NetBSD, OpenBSD, only MAP_ANON exists.
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13 # - On IRIX, neither exists, and a file descriptor opened to /dev/zero must be
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14 # used.
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15
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16 AC_DEFUN([gl_FUNC_MMAP_ANON],
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17 [
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18 dnl Work around a bug of AC_EGREP_CPP in autoconf-2.57.
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19 AC_REQUIRE([AC_PROG_CPP])
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20 AC_REQUIRE([AC_PROG_EGREP])
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21
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22 dnl Persuade glibc <sys/mman.h> to define MAP_ANONYMOUS.
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23 AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
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24
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25 # Check for mmap(). Don't use AC_FUNC_MMAP, because it checks too much: it
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26 # fails on HP-UX 11, because MAP_FIXED mappings do not work. But this is
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27 # irrelevant for anonymous mappings.
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28 AC_CHECK_FUNC([mmap], [gl_have_mmap=yes], [gl_have_mmap=no])
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29
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30 # Try to allow MAP_ANONYMOUS.
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31 gl_have_mmap_anonymous=no
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32 if test $gl_have_mmap = yes; then
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33 AC_MSG_CHECKING([for MAP_ANONYMOUS])
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34 AC_EGREP_CPP([I cant identify this map.], [
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35 #include <sys/mman.h>
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36 #ifdef MAP_ANONYMOUS
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37 I cant identify this map.
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38 #endif
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39 ],
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40 [gl_have_mmap_anonymous=yes])
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41 if test $gl_have_mmap_anonymous != yes; then
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42 AC_EGREP_CPP([I cant identify this map.], [
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43 #include <sys/mman.h>
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44 #ifdef MAP_ANON
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45 I cant identify this map.
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46 #endif
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47 ],
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48 [AC_DEFINE([MAP_ANONYMOUS], [MAP_ANON],
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49 [Define to a substitute value for mmap()'s MAP_ANONYMOUS flag.])
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50 gl_have_mmap_anonymous=yes])
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51 fi
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52 AC_MSG_RESULT([$gl_have_mmap_anonymous])
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53 if test $gl_have_mmap_anonymous = yes; then
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54 AC_DEFINE([HAVE_MAP_ANONYMOUS], [1],
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55 [Define to 1 if mmap()'s MAP_ANONYMOUS flag is available after including
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56 config.h and <sys/mman.h>.])
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57 fi
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58 fi
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59 ])
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