m4/dirfd.m4

   1 #serial 1
   2
   3 dnl Find out how to get the file descriptor associated with an open DIR*.
   4 dnl From Jim Meyering
   5
   6 AC_DEFUN([UTILS_FUNC_DIRFD],
   7 [
   8   AC_HEADER_DIRENT
   9   AC_REPLACE_FUNCS([dirfd])
  10   dirfd_headers='
  11 #if HAVE_DIRENT_H
  12 # include <dirent.h>
  13 #else /* not HAVE_DIRENT_H */
  14 # define dirent direct
  15 # if HAVE_SYS_NDIR_H
  16 #  include <sys/ndir.h>
  17 # endif /* HAVE_SYS_NDIR_H */
  18 # if HAVE_SYS_DIR_H
  19 #  include <sys/dir.h>
  20 # endif /* HAVE_SYS_DIR_H */
  21 # if HAVE_NDIR_H
  22 #  include <ndir.h>
  23 # endif /* HAVE_NDIR_H */
  24 #endif /* HAVE_DIRENT_H */
  25 '
  26   AC_CHECK_DECLS([dirfd], , , $dirfd_headers)
  27   if test $ac_cv_func_dirfd = no; then
  28     AC_CACHE_CHECK(
  29               [how to get the file descriptor associated with an open DIR*],
  30                    ac_cv_sys_dir_to_fd,
  31       [
  32         dirfd_save_DEFS=$DEFS
  33         for ac_expr in                                          \
  34                                                                 \
  35             '# Solaris'                                         \
  36             'dir_p->d_fd'                                       \
  37                                                                 \
  38             '# Solaris'                                         \
  39             'dir_p->dd_fd'                                      \
  40                                                                 \
  41             '# systems for which the info is not available'     \
  42             -1                                                  \
  43             ; do
  44
  45           # Skip each embedded comment.
  46           case "$ac_expr" in '#'*) continue;; esac
  47
  48           DEFS="$DEFS -DDIR_TO_FD=$ac_expr"
  49           AC_TRY_COMPILE(
  50             [$dirfd_headers
  51             ],
  52             [DIR *dir_p = opendir("."); (void) ($ac_expr);],
  53             dir_fd_done=yes
  54           )
  55           DEFS=$dirfd_save_DEFS
  56           test "$dir_fd_done" = yes && break
  57         done
  58
  59         ac_cv_sys_dir_to_fd=$ac_expr
  60       ]
  61     )
  62     AC_DEFINE_UNQUOTED(DIR_TO_FD,
  63       $ac_cv_sys_dir_to_fd,
  64       [the file descriptor associated with `dir_p'])
  65   fi
  66 ])