Bug/Weak Implementation? popen* routines can't handle simultaneous read/write?

[Nick Craig-Wood]

dmoore <damienlmoore at gmail.com> wrote:
>  On Jun 8, 12:30 pm, Nick Craig-Wood <n... at craig-wood.com> wrote:
> > Windows has a really strange idea of non-blocking IO - it uses
> > something called overlapped io.  You or in the FILE_FLAG_OVERLAPPED
> > flag when you create the file/pipe.  You then pass in overlap buffers
> > for reading writing.
> >
> 
>  the wx guys appear to do it differently (unless FILE_FLAG_OVERLAPPED
>  is implicit in the calls they make)
> 
>  take a look at:
>  http://cvs.wxwidgets.org/viewcvs.cgi/wxWidgets/src/msw/utilsexc.cpp?rev=1.88&content-type=text/vnd.viewcvs-markup
> 
>  a reasonably well-documented wxExecute function handles all the messy
>  win32 api calls and wraps the process in a wxProcess object and the
>  streams in wxInputStream / wxOutputStream (also see the wxExecuteDDE
>  function)

You are right, named pipes seem to have a non blocking mode.

Here is the lowdown from
http://msdn2.microsoft.com/en-US/library/aa365605.aspx

  Both pipe clients and pipe servers can change a pipe handle's wait
  mode by specifying either PIPE_WAIT or PIPE_NOWAIT in a call to the
  SetNamedPipeHandleState function.

  Note The nonblocking-wait mode is supported for compatibility with
  Microsoft® LAN Manager version 2.0. This mode should not be used to
  achieve overlapped input and output (I/O) with named
  pipes. Overlapped I/O should be used instead, because it enables
  time-consuming operations to run in the background after the
  function returns. For more information about overlapped I/O, see
  Synchronous and Overlapped Input and Output.

So it has a nonblocking mode but you shouldn't use it!

-- 
Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick