# fcntl.m4 serial 9

dnl Copyright (C) 2009-2017 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.

# For now, this module ensures that fcntl()

# - supports F_DUPFD correctly

# - supports or emulates F_DUPFD_CLOEXEC

# - supports F_GETFD

# Still to be ported to mingw:

# - F_SETFD

# - F_GETFL, F_SETFL

# - F_GETOWN, F_SETOWN

# - F_GETLK, F_SETLK, F_SETLKW

AC_DEFUN([gl_FUNC_FCNTL],

[

  dnl Persuade glibc to expose F_DUPFD_CLOEXEC.

  AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])

  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])

  AC_REQUIRE([AC_CANONICAL_HOST])

  AC_CHECK_FUNCS_ONCE([fcntl])

  if test $ac_cv_func_fcntl = no; then

    gl_REPLACE_FCNTL

  else

    dnl cygwin 1.5.x F_DUPFD has wrong errno, and allows negative target

    dnl haiku alpha 2 F_DUPFD has wrong errno

    AC_CACHE_CHECK([whether fcntl handles F_DUPFD correctly],

      [gl_cv_func_fcntl_f_dupfd_works],

      [AC_RUN_IFELSE(

         [AC_LANG_PROGRAM(

            [[#include <errno.h>

              #include <fcntl.h>

              #include <limits.h>

              #include <sys/resource.h>

              #include <unistd.h>

              #ifndef RLIM_SAVED_CUR

              # define RLIM_SAVED_CUR RLIM_INFINITY

              #endif

              #ifndef RLIM_SAVED_MAX

              # define RLIM_SAVED_MAX RLIM_INFINITY

              #endif

            ]],

            [[int result = 0;

              int bad_fd = INT_MAX;

              struct rlimit rlim;

              if (getrlimit (RLIMIT_NOFILE, &rlim) == 0

                  && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX

                  && rlim.rlim_cur != RLIM_INFINITY

                  && rlim.rlim_cur != RLIM_SAVED_MAX

                  && rlim.rlim_cur != RLIM_SAVED_CUR)

                bad_fd = rlim.rlim_cur;

              if (fcntl (0, F_DUPFD, -1) != -1) result |= 1;

              if (errno != EINVAL) result |= 2;

              if (fcntl (0, F_DUPFD, bad_fd) != -1) result |= 4;

              if (errno != EINVAL) result |= 8;

              /* On OS/2 kLIBC, F_DUPFD does not work on a directory fd */

              {

                int fd;

                fd = open (".", O_RDONLY);

                if (fd == -1)

                  result |= 16;

                else if (fcntl (fd, F_DUPFD, STDERR_FILENO + 1) == -1)

                  result |= 32;

                close (fd);

              }

              return result;]])],

         [gl_cv_func_fcntl_f_dupfd_works=yes],

         [gl_cv_func_fcntl_f_dupfd_works=no],

         [case $host_os in

            aix* | cygwin* | haiku*)

               gl_cv_func_fcntl_f_dupfd_works="guessing no" ;;

            *) gl_cv_func_fcntl_f_dupfd_works="guessing yes" ;;

          esac])])

    case $gl_cv_func_fcntl_f_dupfd_works in

      *yes) ;;

      *) gl_REPLACE_FCNTL

        AC_DEFINE([FCNTL_DUPFD_BUGGY], [1], [Define this to 1 if F_DUPFD

          behavior does not match POSIX]) ;;

    esac

    dnl Many systems lack F_DUPFD_CLOEXEC

    AC_CACHE_CHECK([whether fcntl understands F_DUPFD_CLOEXEC],

      [gl_cv_func_fcntl_f_dupfd_cloexec],

      [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[

#include <fcntl.h>

#ifndef F_DUPFD_CLOEXEC

choke me

#endif

         ]])],

         [AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[

#ifdef __linux__

/* The Linux kernel only added F_DUPFD_CLOEXEC in 2.6.24, so we always replace

   it to support the semantics on older kernels that failed with EINVAL.  */

choke me

#endif

           ]])],

           [gl_cv_func_fcntl_f_dupfd_cloexec=yes],

           [gl_cv_func_fcntl_f_dupfd_cloexec="needs runtime check"])],

         [gl_cv_func_fcntl_f_dupfd_cloexec=no])])

    if test "$gl_cv_func_fcntl_f_dupfd_cloexec" != yes; then

      gl_REPLACE_FCNTL

      dnl No witness macro needed for this bug.

    fi

  fi

  dnl Replace fcntl() for supporting the gnulib-defined fchdir() function,

  dnl to keep fchdir's bookkeeping up-to-date.

  m4_ifdef([gl_FUNC_FCHDIR], [

    gl_TEST_FCHDIR

    if test $HAVE_FCHDIR = 0; then

      gl_REPLACE_FCNTL

    fi

  ])

])

AC_DEFUN([gl_REPLACE_FCNTL],

[

  AC_REQUIRE([gl_FCNTL_H_DEFAULTS])

  AC_CHECK_FUNCS_ONCE([fcntl])

  if test $ac_cv_func_fcntl = no; then

    HAVE_FCNTL=0

  else

    REPLACE_FCNTL=1

  fi

])