pipe-posix: Make it work in C++ mode. * lib/unistd.in.h: Don't include <io.h>, <fcntl.h> for pipe. (pipe): Use common idiom, not a macro definition. * lib/pipe.c: New file. * m4/pipe.m4: New file. * modules/pipe-posix (Description): Enhance. (Files): Add lib/pipe.c, m4/pipe.m4. (configure.ac): Invoke gl_FUNC_PIPE. * m4/unistd_h.m4 (gl_UNISTD_H_DEFAULTS): Initialize HAVE_PIPE. * modules/unistd (Makefile.am): Substitute HAVE_PIPE. * tests/test-unistd-c++.cc: Check the signature of pipe.

# pipe.m4 serial 1
dnl Copyright (C) 2010 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_PIPE],
[
  AC_REQUIRE([gl_UNISTD_H_DEFAULTS])

  AC_CHECK_FUNCS_ONCE([pipe])
  if test $ac_cv_func_pipe != yes; then
    HAVE_PIPE=0
    AC_LIBOBJ([pipe])
  fi
])