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Diffstat (limited to '')
-rw-r--r-- | m4/mmap-anon.m4 | 55 |
1 files changed, 55 insertions, 0 deletions
diff --git a/m4/mmap-anon.m4 b/m4/mmap-anon.m4 new file mode 100644 index 0000000..a4580ff --- /dev/null +++ b/m4/mmap-anon.m4 @@ -0,0 +1,55 @@ +# mmap-anon.m4 serial 12 +dnl Copyright (C) 2005, 2007, 2009-2022 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. + +# Detect how mmap can be used to create anonymous (not file-backed) memory +# mappings. +# - On Linux, AIX, OSF/1, Solaris, Cygwin, Interix, Haiku, both MAP_ANONYMOUS +# and MAP_ANON exist and have the same value. +# - On HP-UX, only MAP_ANONYMOUS exists. +# - On Mac OS X, FreeBSD, NetBSD, OpenBSD, Minix, only MAP_ANON exists. +# - On IRIX, neither exists, and a file descriptor opened to /dev/zero must be +# used. + +AC_DEFUN_ONCE([gl_FUNC_MMAP_ANON], +[ + dnl Persuade glibc <sys/mman.h> to define MAP_ANONYMOUS. + AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS]) + + # Check for mmap(). Don't use AC_FUNC_MMAP, because it checks too much: it + # fails on HP-UX 11, because MAP_FIXED mappings do not work. But this is + # irrelevant for anonymous mappings. + AC_CHECK_FUNC([mmap], [gl_have_mmap=yes], [gl_have_mmap=no]) + + # Try to allow MAP_ANONYMOUS. + gl_have_mmap_anonymous=no + if test $gl_have_mmap = yes; then + AC_MSG_CHECKING([for MAP_ANONYMOUS]) + AC_EGREP_CPP([I cannot identify this map], [ +#include <sys/mman.h> +#ifdef MAP_ANONYMOUS + I cannot identify this map +#endif +], + [gl_have_mmap_anonymous=yes]) + if test $gl_have_mmap_anonymous != yes; then + AC_EGREP_CPP([I cannot identify this map], [ +#include <sys/mman.h> +#ifdef MAP_ANON + I cannot identify this map +#endif +], + [AC_DEFINE([MAP_ANONYMOUS], [MAP_ANON], + [Define to a substitute value for mmap()'s MAP_ANONYMOUS flag.]) + gl_have_mmap_anonymous=yes]) + fi + AC_MSG_RESULT([$gl_have_mmap_anonymous]) + if test $gl_have_mmap_anonymous = yes; then + AC_DEFINE([HAVE_MAP_ANONYMOUS], [1], + [Define to 1 if mmap()'s MAP_ANONYMOUS flag is available after including + config.h and <sys/mman.h>.]) + fi + fi +]) |