dup2, dup3: work around another cygwin crasher Cygwin 1.7.25 can crash due to an off-by-one bug on an attempt to duplicate a file into the current RLIMIT_NOFILE soft limit, when that limit is smaller than the hard limit. The intent in the cygwin code was to allow the dup and auto-increase the soft limit, which is itself questionable (and which we work around in the gnulib getdtablesize module); but avoiding the crash is worth doing even if the soft limit semantics are wrong. http://cygwin.com/ml/cygwin/2013-09/msg00397.html http://cygwin.com/ml/cygwin-developers/2013-q3/msg00010.html * m4/dup2.m4 (gl_FUNC_DUP2): Expose the bug. * m4/dup3.m4 (gl_FUNC_DUP3): Likewise. * tests/test-dup2.c (main): Likewise. * lib/dup2.c (rpl_dup2): Use setdtablesize to avoid it. * lib/dup3.c (dup3): Likewise. * doc/posix-functions/dup2.texi (dup2): Document it. * doc/glibc-functions/dup3.texi (dup3): Likewise. Signed-off-by: Eric Blake <eblake@redhat.com>

# dup3.m4 serial 5
dnl Copyright (C) 2009-2013 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_DUP3],
[
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])

  dnl Persuade glibc <unistd.h> to declare dup3().
  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])

  AC_CHECK_FUNCS_ONCE([dup3 setdtablesize])
  if test $ac_cv_func_dup3 != yes; then
    HAVE_DUP3=0
  fi

dnl Not needed yet, because dup3 is unconditionally replaced.
dnl  dnl Replace dup3() for supporting the gnulib-defined fchdir() function,
dnl  dnl to keep fchdir's bookkeeping up-to-date.
dnl  m4_ifdef([gl_FUNC_FCHDIR], [
dnl    gl_TEST_FCHDIR
dnl    if test $HAVE_FCHDIR = 0; then
dnl      if test $HAVE_DUP3 = 1; then
dnl        REPLACE_DUP3=1
dnl      fi
dnl    fi
dnl  ])
])