#serial 25

dnl Copyright (C) 2002, 2005, 2007, 2009-2020 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.

AC_DEFUN([gl_FUNC_DUP2],

[

  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])

  AC_REQUIRE([AC_CANONICAL_HOST])

  m4_ifdef([gl_FUNC_DUP2_OBSOLETE], [

    AC_CHECK_FUNCS_ONCE([dup2])

    if test $ac_cv_func_dup2 = no; then

      HAVE_DUP2=0

    fi

  ], [

    AC_DEFINE([HAVE_DUP2], [1], [Define to 1 if you have the 'dup2' function.])

  ])

  if test $HAVE_DUP2 = 1; then

    AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_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;

             #ifdef FD_CLOEXEC

               if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)

                 result |= 1;

             #endif

             if (dup2 (1, 1) != 1)

               result |= 2;

             #ifdef FD_CLOEXEC

               if (fcntl (1, F_GETFD) != FD_CLOEXEC)

                 result |= 4;

             #endif

             close (0);

             if (dup2 (0, 0) != -1)

               result |= 8;

             /* Many gnulib modules require POSIX conformance of EBADF.  */

             if (dup2 (2, bad_fd) == -1 && errno != EBADF)

               result |= 16;

             /* Flush out some cygwin core dumps.  */

             if (dup2 (2, -1) != -1 || errno != EBADF)

               result |= 32;

             dup2 (2, 255);

             dup2 (2, 256);

             /* On OS/2 kLIBC, dup2() does not work on a directory fd.  */

             {

               int fd = open (".", O_RDONLY);

               if (fd == -1)

                 result |= 64;

               else if (dup2 (fd, fd + 1) == -1)

                 result |= 128;

               close (fd);

             }

             return result;]])

        ],

        [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],

        [case "$host_os" in

           mingw*) # on this platform, dup2 always returns 0 for success

             gl_cv_func_dup2_works="guessing no" ;;

           cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0

             gl_cv_func_dup2_works="guessing no" ;;

           aix* | freebsd*)

                   # on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,

                   # not EBADF.

             gl_cv_func_dup2_works="guessing no" ;;

           haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.

             gl_cv_func_dup2_works="guessing no" ;;

           *-android*) # implemented using dup3(), which fails if oldfd == newfd

             gl_cv_func_dup2_works="guessing no" ;;

           os2*) # on OS/2 kLIBC, dup2() does not work on a directory fd.

             gl_cv_func_dup2_works="guessing no" ;;

           *) gl_cv_func_dup2_works="guessing yes" ;;

         esac])

      ])

    case "$gl_cv_func_dup2_works" in

      *yes) ;;

      *)

        REPLACE_DUP2=1

        AC_CHECK_FUNCS([setdtablesize])

        ;;

    esac

  fi

  dnl Replace dup2() 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

      if test $HAVE_DUP2 = 1; then

        REPLACE_DUP2=1

      fi

    fi

  ])

])

# Prerequisites of lib/dup2.c.

AC_DEFUN([gl_PREREQ_DUP2], [])