config/mmap.m4

   1 dnl ----------------------------------------------------------------------
   2 dnl This whole bit snagged from gcc
   3
   4 dnl
   5 dnl mmap(2) blacklisting.  Some platforms provide the mmap library routine
   6 dnl but don't support all of the features we need from it.
   7 dnl
   8 AC_DEFUN([GCC_AC_FUNC_MMAP_BLACKLIST],
   9 [
  10 AC_CHECK_HEADER([sys/mman.h],
  11                 [gcc_header_sys_mman_h=yes], [gcc_header_sys_mman_h=no])
  12 AC_CHECK_FUNC([mmap], [gcc_func_mmap=yes], [gcc_func_mmap=no])
  13 if test "$gcc_header_sys_mman_h" != yes \
  14  || test "$gcc_func_mmap" != yes; then
  15    gcc_cv_func_mmap_file=no
  16    gcc_cv_func_mmap_dev_zero=no
  17    gcc_cv_func_mmap_anon=no
  18 else
  19    AC_CACHE_CHECK([whether read-only mmap of a plain file works],
  20   gcc_cv_func_mmap_file,
  21   [# Add a system to this blacklist if
  22    # mmap(0, stat_size, PROT_READ, MAP_PRIVATE, fd, 0) doesn't return a
  23    # memory area containing the same data that you'd get if you applied
  24    # read() to the same fd.  The only system known to have a problem here
  25    # is VMS, where text files have record structure.
  26    case "$host_os" in
  27      *vms* | ultrix*)
  28         gcc_cv_func_mmap_file=no ;;
  29      *)
  30         gcc_cv_func_mmap_file=yes;;
  31    esac])
  32    AC_CACHE_CHECK([whether mmap from /dev/zero works],
  33   gcc_cv_func_mmap_dev_zero,
  34   [# Add a system to this blacklist if it has mmap() but /dev/zero
  35    # does not exist, or if mmapping /dev/zero does not give anonymous
  36    # zeroed pages with both the following properties:
  37    # 1. If you map N consecutive pages in with one call, and then
  38    #    unmap any subset of those pages, the pages that were not
  39    #    explicitly unmapped remain accessible.
  40    # 2. If you map two adjacent blocks of memory and then unmap them
  41    #    both at once, they must both go away.
  42    # Systems known to be in this category are Windows (all variants),
  43    # VMS, and Darwin.
  44    case "$host_os" in
  45      *vms* | cygwin* | pe | mingw* | darwin* | ultrix* | hpux10* | hpux11.00)
  46         gcc_cv_func_mmap_dev_zero=no ;;
  47      *)
  48         gcc_cv_func_mmap_dev_zero=yes;;
  49    esac])
  50
  51    # Unlike /dev/zero, the MAP_ANON(YMOUS) defines can be probed for.
  52    AC_CACHE_CHECK([for MAP_ANON(YMOUS)], gcc_cv_decl_map_anon,
  53     [AC_COMPILE_IFELSE([AC_LANG_PROGRAM(
  54 [#include <sys/types.h>
  55 #include <sys/mman.h>
  56 #include <unistd.h>
  57
  58 #ifndef MAP_ANONYMOUS
  59 #define MAP_ANONYMOUS MAP_ANON
  60 #endif
  61 ],
  62 [int n = MAP_ANONYMOUS;])],
  63     gcc_cv_decl_map_anon=yes,
  64     gcc_cv_decl_map_anon=no)])
  65
  66    if test $gcc_cv_decl_map_anon = no; then
  67      gcc_cv_func_mmap_anon=no
  68    else
  69      AC_CACHE_CHECK([whether mmap with MAP_ANON(YMOUS) works],
  70      gcc_cv_func_mmap_anon,
  71   [# Add a system to this blacklist if it has mmap() and MAP_ANON or
  72    # MAP_ANONYMOUS, but using mmap(..., MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
  73    # doesn't give anonymous zeroed pages with the same properties listed
  74    # above for use of /dev/zero.
  75    # Systems known to be in this category are Windows, VMS, and SCO Unix.
  76    case "$host_os" in
  77      *vms* | cygwin* | pe | mingw* | sco* | udk* )
  78         gcc_cv_func_mmap_anon=no ;;
  79      *)
  80         gcc_cv_func_mmap_anon=yes;;
  81    esac])
  82    fi
  83 fi
  84
  85 if test $gcc_cv_func_mmap_file = yes; then
  86   AC_DEFINE(HAVE_MMAP_FILE, 1,
  87             [Define if read-only mmap of a plain file works.])
  88 fi
  89 if test $gcc_cv_func_mmap_dev_zero = yes; then
  90   AC_DEFINE(HAVE_MMAP_DEV_ZERO, 1,
  91             [Define if mmap of /dev/zero works.])
  92 fi
  93 if test $gcc_cv_func_mmap_anon = yes; then
  94   AC_DEFINE(HAVE_MMAP_ANON, 1,
  95             [Define if mmap with MAP_ANON(YMOUS) works.])
  96 fi
  97 ])