# getdtablesize.m4 serial 7

dnl Copyright (C) 2008-2018 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.

AC_DEFUN([gl_FUNC_GETDTABLESIZE],

[

  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])

  AC_REQUIRE([AC_CANONICAL_HOST])

  AC_CHECK_FUNCS_ONCE([getdtablesize])

  AC_CHECK_DECLS_ONCE([getdtablesize])

  if test $ac_cv_func_getdtablesize = yes &&

     test $ac_cv_have_decl_getdtablesize = yes; then

    AC_CACHE_CHECK([whether getdtablesize works],

      [gl_cv_func_getdtablesize_works],

      [dnl There are two concepts: the "maximum possible file descriptor value + 1"

       dnl and the "maximum number of open file descriptors in a process".

       dnl Per SUSv2 and POSIX, getdtablesize() should return the first one.

       dnl On most platforms, the first and the second concept are the same.

       dnl On OpenVMS, however, they are different and getdtablesize() returns

       dnl the second one; thus the test below fails. But we don't care

       dnl because there's no good way to write a replacement getdtablesize().

       case "$host_os" in

         vms*) gl_cv_func_getdtablesize_works="no (limitation)" ;;

         *)

           dnl Cygwin 1.7.25 automatically increases the RLIMIT_NOFILE soft

           dnl limit up to an unchangeable hard limit; all other platforms

           dnl correctly require setrlimit before getdtablesize() can report

           dnl a larger value.

           AC_RUN_IFELSE([

             AC_LANG_PROGRAM([[#include <unistd.h>]],

               [int size = getdtablesize();

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

                  return 1;

                if (size != getdtablesize())

                  return 2;

               ])],

             [gl_cv_func_getdtablesize_works=yes],

             [gl_cv_func_getdtablesize_works=no],

             [case "$host_os" in

                cygwin*) # on cygwin 1.5.25, getdtablesize() automatically grows

                  gl_cv_func_getdtablesize_works="guessing no" ;;

                *) gl_cv_func_getdtablesize_works="guessing yes" ;;

              esac

             ])

           ;;

       esac

      ])

    case "$gl_cv_func_getdtablesize_works" in

      *yes | "no (limitation)") ;;

      *) REPLACE_GETDTABLESIZE=1 ;;

    esac

  else

    HAVE_GETDTABLESIZE=0

  fi

])

# Prerequisites of lib/getdtablesize.c.

AC_DEFUN([gl_PREREQ_GETDTABLESIZE], [:])