1# getdtablesize.m4 serial 7 2dnl Copyright (C) 2008-2020 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([[#include <unistd.h>]], 33 [int size = getdtablesize(); 34 if (dup2 (0, getdtablesize()) != -1) 35 return 1; 36 if (size != getdtablesize()) 37 return 2; 38 ])], 39 [gl_cv_func_getdtablesize_works=yes], 40 [gl_cv_func_getdtablesize_works=no], 41 [case "$host_os" in 42 cygwin*) # on cygwin 1.5.25, getdtablesize() automatically grows 43 gl_cv_func_getdtablesize_works="guessing no" ;; 44 *) gl_cv_func_getdtablesize_works="guessing yes" ;; 45 esac 46 ]) 47 ;; 48 esac 49 ]) 50 case "$gl_cv_func_getdtablesize_works" in 51 *yes | "no (limitation)") ;; 52 *) REPLACE_GETDTABLESIZE=1 ;; 53 esac 54 else 55 HAVE_GETDTABLESIZE=0 56 fi 57]) 58 59# Prerequisites of lib/getdtablesize.c. 60AC_DEFUN([gl_PREREQ_GETDTABLESIZE], [:]) 61