| 1 | # mmap-anon.m4 serial 12
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| 2 | dnl Copyright (C) 2005, 2007, 2009-2022 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 Mac OS X, FreeBSD, NetBSD, OpenBSD, Minix, 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_ONCE([gl_FUNC_MMAP_ANON],
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| 17 | [
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| 18 | dnl Persuade glibc <sys/mman.h> to define MAP_ANONYMOUS.
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| 19 | AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
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| 20 |
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| 21 | # Check for mmap(). Don't use AC_FUNC_MMAP, because it checks too much: it
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| 22 | # fails on HP-UX 11, because MAP_FIXED mappings do not work. But this is
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| 23 | # irrelevant for anonymous mappings.
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| 24 | AC_CHECK_FUNC([mmap], [gl_have_mmap=yes], [gl_have_mmap=no])
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| 25 |
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| 26 | # Try to allow MAP_ANONYMOUS.
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| 27 | gl_have_mmap_anonymous=no
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| 28 | if test $gl_have_mmap = yes; then
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| 29 | AC_MSG_CHECKING([for MAP_ANONYMOUS])
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| 30 | AC_EGREP_CPP([I cannot identify this map], [
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| 31 | #include <sys/mman.h>
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| 32 | #ifdef MAP_ANONYMOUS
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| 33 | I cannot identify this map
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| 34 | #endif
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| 35 | ],
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| 36 | [gl_have_mmap_anonymous=yes])
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| 37 | if test $gl_have_mmap_anonymous != yes; then
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| 38 | AC_EGREP_CPP([I cannot identify this map], [
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| 39 | #include <sys/mman.h>
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| 40 | #ifdef MAP_ANON
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| 41 | I cannot identify this map
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| 42 | #endif
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| 43 | ],
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| 44 | [AC_DEFINE([MAP_ANONYMOUS], [MAP_ANON],
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| 45 | [Define to a substitute value for mmap()'s MAP_ANONYMOUS flag.])
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| 46 | gl_have_mmap_anonymous=yes])
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| 47 | fi
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| 48 | AC_MSG_RESULT([$gl_have_mmap_anonymous])
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| 49 | if test $gl_have_mmap_anonymous = yes; then
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| 50 | AC_DEFINE([HAVE_MAP_ANONYMOUS], [1],
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| 51 | [Define to 1 if mmap()'s MAP_ANONYMOUS flag is available after including
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| 52 | config.h and <sys/mman.h>.])
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| 53 | fi
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| 54 | fi
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| 55 | ])
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