m4/fcntl-o.m4

   1 # fcntl-o.m4 serial 3
   2 dnl Copyright (C) 2006, 2009-2011 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl with or without modifications, as long as this notice is preserved.
   6
   7 dnl Written by Paul Eggert.
   8
   9 # Test whether the flags O_NOATIME and O_NOFOLLOW actually work.
  10 # Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise.
  11 # Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise.
  12 AC_DEFUN([gl_FCNTL_O_FLAGS],
  13 [
  14   dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW.
  15   dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes
  16   dnl AC_GNU_SOURCE.
  17   m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],
  18     [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],
  19     [AC_REQUIRE([AC_GNU_SOURCE])])
  20   AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],
  21     [AC_RUN_IFELSE(
  22        [AC_LANG_PROGRAM(
  23           [[#include <sys/types.h>
  24            #include <sys/stat.h>
  25            #include <unistd.h>
  26            #include <fcntl.h>
  27            #ifndef O_NOATIME
  28             #define O_NOATIME 0
  29            #endif
  30            #ifndef O_NOFOLLOW
  31             #define O_NOFOLLOW 0
  32            #endif
  33            static int const constants[] =
  34             {
  35               O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC, O_APPEND,
  36               O_NONBLOCK, O_SYNC, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY
  37             };
  38           ]],
  39           [[
  40             int result = !constants;
  41             {
  42               static char const sym[] = "conftest.sym";
  43               if (symlink (".", sym) != 0)
  44                 result |= 2;
  45               else
  46                 {
  47                   int fd = open (sym, O_RDONLY | O_NOFOLLOW);
  48                   if (fd >= 0)
  49                     {
  50                       close (fd);
  51                       result |= 4;
  52                     }
  53                 }
  54               unlink (sym);
  55             }
  56             {
  57               static char const file[] = "confdefs.h";
  58               int fd = open (file, O_RDONLY | O_NOATIME);
  59               if (fd < 0)
  60                 result |= 8;
  61               else
  62                 {
  63                   struct stat st0;
  64                   if (fstat (fd, &st0) != 0)
  65                     result |= 16;
  66                   else
  67                     {
  68                       char c;
  69                       sleep (1);
  70                       if (read (fd, &c, 1) != 1)
  71                         result |= 24;
  72                       else
  73                         {
  74                           if (close (fd) != 0)
  75                             result |= 32;
  76                           else
  77                             {
  78                               struct stat st1;
  79                               if (stat (file, &st1) != 0)
  80                                 result |= 40;
  81                               else
  82                                 if (st0.st_atime != st1.st_atime)
  83                                   result |= 64;
  84                             }
  85                         }
  86                     }
  87                 }
  88             }
  89             return result;]])],
  90        [gl_cv_header_working_fcntl_h=yes],
  91        [case $? in #(
  92         4) gl_cv_header_working_fcntl_h='no (bad O_NOFOLLOW)';; #(
  93         64) gl_cv_header_working_fcntl_h='no (bad O_NOATIME)';; #(
  94         68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #(
  95          *) gl_cv_header_working_fcntl_h='no';;
  96         esac],
  97        [gl_cv_header_working_fcntl_h=cross-compiling])])
  98
  99   case $gl_cv_header_working_fcntl_h in #(
 100   *O_NOATIME* | no | cross-compiling) ac_val=0;; #(
 101   *) ac_val=1;;
 102   esac
 103   AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOATIME], [$ac_val],
 104     [Define to 1 if O_NOATIME works.])
 105
 106   case $gl_cv_header_working_fcntl_h in #(
 107   *O_NOFOLLOW* | no | cross-compiling) ac_val=0;; #(
 108   *) ac_val=1;;
 109   esac
 110   AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOFOLLOW], [$ac_val],
 111     [Define to 1 if O_NOFOLLOW works.])
 112 ])