1# getdtablesize.m4 serial 8
2dnl Copyright (C) 2008-2021 Free Software Foundation, Inc.
3dnl This file is free software; the Free Software Foundation
4dnl gives unlimited permission to copy and/or distribute it,
5dnl with or without modifications, as long as this notice is preserved.
6
7AC_DEFUN([gl_FUNC_GETDTABLESIZE],
8[
9  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
10  AC_REQUIRE([AC_CANONICAL_HOST])
11  AC_CHECK_FUNCS_ONCE([getdtablesize])
12  AC_CHECK_DECLS_ONCE([getdtablesize])
13  if test $ac_cv_func_getdtablesize = yes &&
14     test $ac_cv_have_decl_getdtablesize = yes; then
15    AC_CACHE_CHECK([whether getdtablesize works],
16      [gl_cv_func_getdtablesize_works],
17      [dnl There are two concepts: the "maximum possible file descriptor value + 1"
18       dnl and the "maximum number of open file descriptors in a process".
19       dnl Per SUSv2 and POSIX, getdtablesize() should return the first one.
20       dnl On most platforms, the first and the second concept are the same.
21       dnl On OpenVMS, however, they are different and getdtablesize() returns
22       dnl the second one; thus the test below fails. But we don't care
23       dnl because there's no good way to write a replacement getdtablesize().
24       case "$host_os" in
25         vms*) gl_cv_func_getdtablesize_works="no (limitation)" ;;
26         *)
27           dnl Cygwin 1.7.25 automatically increases the RLIMIT_NOFILE soft
28           dnl limit up to an unchangeable hard limit; all other platforms
29           dnl correctly require setrlimit before getdtablesize() can report
30           dnl a larger value.
31           AC_RUN_IFELSE([
32             AC_LANG_PROGRAM(
33               [[#include <unistd.h>]
34                GL_MDA_DEFINES
35               ],
36               [[int size = getdtablesize();
37                 if (dup2 (0, getdtablesize()) != -1)
38                   return 1;
39                 if (size != getdtablesize())
40                   return 2;
41               ]])],
42             [gl_cv_func_getdtablesize_works=yes],
43             [gl_cv_func_getdtablesize_works=no],
44             [case "$host_os" in
45                cygwin*) # on cygwin 1.5.25, getdtablesize() automatically grows
46                  gl_cv_func_getdtablesize_works="guessing no" ;;
47                *) gl_cv_func_getdtablesize_works="guessing yes" ;;
48              esac
49             ])
50           ;;
51       esac
52      ])
53    case "$gl_cv_func_getdtablesize_works" in
54      *yes | "no (limitation)") ;;
55      *) REPLACE_GETDTABLESIZE=1 ;;
56    esac
57  else
58    HAVE_GETDTABLESIZE=0
59  fi
60])
61
62# Prerequisites of lib/getdtablesize.c.
63AC_DEFUN([gl_PREREQ_GETDTABLESIZE], [:])
64