github.com/prattmic/llgo-embedded@v0.0.0-20150820070356-41cfecea0e1e/third_party/gofrontend/libffi/acinclude.m4 (about)

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