# fcntl-o.m4 serial 5

dnl Copyright (C) 2006, 2009-2018 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.

dnl Written by Paul Eggert.

# Test whether the flags O_NOATIME and O_NOFOLLOW actually work.

# Define HAVE_WORKING_O_NOATIME to 1 if O_NOATIME works, or to 0 otherwise.

# Define HAVE_WORKING_O_NOFOLLOW to 1 if O_NOFOLLOW works, or to 0 otherwise.

AC_DEFUN([gl_FCNTL_O_FLAGS],

[

  dnl Persuade glibc <fcntl.h> to define O_NOATIME and O_NOFOLLOW.

  dnl AC_USE_SYSTEM_EXTENSIONS was introduced in autoconf 2.60 and obsoletes

  dnl AC_GNU_SOURCE.

  m4_ifdef([AC_USE_SYSTEM_EXTENSIONS],

    [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])],

    [AC_REQUIRE([AC_GNU_SOURCE])])

  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles

  AC_CHECK_HEADERS_ONCE([unistd.h])

  AC_CHECK_FUNCS_ONCE([symlink])

  AC_CACHE_CHECK([for working fcntl.h], [gl_cv_header_working_fcntl_h],

    [AC_RUN_IFELSE(

       [AC_LANG_PROGRAM(

          [[#include <sys/types.h>

           #include <sys/stat.h>

           #if HAVE_UNISTD_H

           # include <unistd.h>

           #else /* on Windows with MSVC */

           # include <io.h>

           # include <stdlib.h>

           # defined sleep(n) _sleep ((n) * 1000)

           #endif

           #include <fcntl.h>

           #ifndef O_NOATIME

            #define O_NOATIME 0

           #endif

           #ifndef O_NOFOLLOW

            #define O_NOFOLLOW 0

           #endif

           static int const constants[] =

            {

              O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC, O_APPEND,

              O_NONBLOCK, O_SYNC, O_ACCMODE, O_RDONLY, O_RDWR, O_WRONLY

            };

          ]],

          [[

            int result = !constants;

            #if HAVE_SYMLINK

            {

              static char const sym[] = "conftest.sym";

              if (symlink ("/dev/null", sym) != 0)

                result |= 2;

              else

                {

                  int fd = open (sym, O_WRONLY | O_NOFOLLOW | O_CREAT, 0);

                  if (fd >= 0)

                    {

                      close (fd);

                      result |= 4;

                    }

                }

              if (unlink (sym) != 0 || symlink (".", sym) != 0)

                result |= 2;

              else

                {

                  int fd = open (sym, O_RDONLY | O_NOFOLLOW);

                  if (fd >= 0)

                    {

                      close (fd);

                      result |= 4;

                    }

                }

              unlink (sym);

            }

            #endif

            {

              static char const file[] = "confdefs.h";

              int fd = open (file, O_RDONLY | O_NOATIME);

              if (fd < 0)

                result |= 8;

              else

                {

                  struct stat st0;

                  if (fstat (fd, &st0) != 0)

                    result |= 16;

                  else

                    {

                      char c;

                      sleep (1);

                      if (read (fd, &c, 1) != 1)

                        result |= 24;

                      else

                        {

                          if (close (fd) != 0)

                            result |= 32;

                          else

                            {

                              struct stat st1;

                              if (stat (file, &st1) != 0)

                                result |= 40;

                              else

                                if (st0.st_atime != st1.st_atime)

                                  result |= 64;

                            }

                        }

                    }

                }

            }

            return result;]])],

       [gl_cv_header_working_fcntl_h=yes],

       [case $? in #(

        4) gl_cv_header_working_fcntl_h='no (bad O_NOFOLLOW)';; #(

        64) gl_cv_header_working_fcntl_h='no (bad O_NOATIME)';; #(

        68) gl_cv_header_working_fcntl_h='no (bad O_NOATIME, O_NOFOLLOW)';; #(

         *) gl_cv_header_working_fcntl_h='no';;

        esac],

       [case "$host_os" in

                  # Guess 'no' on native Windows.

          mingw*) gl_cv_header_working_fcntl_h='no' ;;

          *)      gl_cv_header_working_fcntl_h=cross-compiling ;;

        esac

       ])

    ])

  case $gl_cv_header_working_fcntl_h in #(

  *O_NOATIME* | no | cross-compiling) ac_val=0;; #(

  *) ac_val=1;;

  esac

  AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOATIME], [$ac_val],

    [Define to 1 if O_NOATIME works.])

  case $gl_cv_header_working_fcntl_h in #(

  *O_NOFOLLOW* | no | cross-compiling) ac_val=0;; #(

  *) ac_val=1;;

  esac

  AC_DEFINE_UNQUOTED([HAVE_WORKING_O_NOFOLLOW], [$ac_val],

    [Define to 1 if O_NOFOLLOW works.])

])