code.delx.au - gnu-emacs/blob - m4/dup2.m4

   1 #serial 22
   2 dnl Copyright (C) 2002, 2005, 2007, 2009-2015 Free Software Foundation, Inc.
   3 dnl This file is free software; the Free Software Foundation
   4 dnl gives unlimited permission to copy and/or distribute it,
   5 dnl with or without modifications, as long as this notice is preserved.
   6
   7 AC_DEFUN([gl_FUNC_DUP2],
   8 [
   9   AC_REQUIRE([gl_UNISTD_H_DEFAULTS])
  10   AC_REQUIRE([AC_CANONICAL_HOST])
  11   m4_ifdef([gl_FUNC_DUP2_OBSOLETE], [
  12     AC_CHECK_FUNCS_ONCE([dup2])
  13     if test $ac_cv_func_dup2 = no; then
  14       HAVE_DUP2=0
  15     fi
  16   ], [
  17     AC_DEFINE([HAVE_DUP2], [1], [Define to 1 if you have the 'dup2' function.])
  18   ])
  19   if test $HAVE_DUP2 = 1; then
  20     AC_CACHE_CHECK([whether dup2 works], [gl_cv_func_dup2_works],
  21       [AC_RUN_IFELSE([
  22          AC_LANG_PROGRAM(
  23            [[#include <errno.h>
  24              #include <fcntl.h>
  25              #include <limits.h>
  26              #include <sys/resource.h>
  27              #include <unistd.h>
  28            ]],
  29            [[int result = 0;
  30              int bad_fd = INT_MAX;
  31              struct rlimit rlim;
  32              if (getrlimit (RLIMIT_NOFILE, &rlim) == 0
  33                  && 0 <= rlim.rlim_cur && rlim.rlim_cur <= INT_MAX
  34                  && rlim.rlim_cur != RLIM_INFINITY
  35                  && rlim.rlim_cur != RLIM_SAVED_MAX
  36                  && rlim.rlim_cur != RLIM_SAVED_CUR)
  37                bad_fd = rlim.rlim_cur;
  38              #ifdef FD_CLOEXEC
  39                if (fcntl (1, F_SETFD, FD_CLOEXEC) == -1)
  40                  result |= 1;
  41              #endif
  42              if (dup2 (1, 1) == 0)
  43                result |= 2;
  44              #ifdef FD_CLOEXEC
  45                if (fcntl (1, F_GETFD) != FD_CLOEXEC)
  46                  result |= 4;
  47              #endif
  48              close (0);
  49              if (dup2 (0, 0) != -1)
  50                result |= 8;
  51              /* Many gnulib modules require POSIX conformance of EBADF.  */
  52              if (dup2 (2, bad_fd) == -1 && errno != EBADF)
  53                result |= 16;
  54              /* Flush out some cygwin core dumps.  */
  55              if (dup2 (2, -1) != -1 || errno != EBADF)
  56                result |= 32;
  57              dup2 (2, 255);
  58              dup2 (2, 256);
  59              return result;]])
  60         ],
  61         [gl_cv_func_dup2_works=yes], [gl_cv_func_dup2_works=no],
  62         [case "$host_os" in
  63            mingw*) # on this platform, dup2 always returns 0 for success
  64              gl_cv_func_dup2_works="guessing no" ;;
  65            cygwin*) # on cygwin 1.5.x, dup2(1,1) returns 0
  66              gl_cv_func_dup2_works="guessing no" ;;
  67            aix* | freebsd*)
  68                    # on AIX 7.1 and FreeBSD 6.1, dup2 (1,toobig) gives EMFILE,
  69                    # not EBADF.
  70              gl_cv_func_dup2_works="guessing no" ;;
  71            haiku*) # on Haiku alpha 2, dup2(1, 1) resets FD_CLOEXEC.
  72              gl_cv_func_dup2_works="guessing no" ;;
  73            *) gl_cv_func_dup2_works="guessing yes" ;;
  74          esac])
  75       ])
  76     case "$gl_cv_func_dup2_works" in
  77       *yes) ;;
  78       *)
  79         REPLACE_DUP2=1
  80         AC_CHECK_FUNCS([setdtablesize])
  81         ;;
  82     esac
  83   fi
  84   dnl Replace dup2() for supporting the gnulib-defined fchdir() function,
  85   dnl to keep fchdir's bookkeeping up-to-date.
  86   m4_ifdef([gl_FUNC_FCHDIR], [
  87     gl_TEST_FCHDIR
  88     if test $HAVE_FCHDIR = 0; then
  89       if test $HAVE_DUP2 = 1; then
  90         REPLACE_DUP2=1
  91       fi
  92     fi
  93   ])
  94 ])
  95
  96 # Prerequisites of lib/dup2.c.
  97 AC_DEFUN([gl_PREREQ_DUP2], [])