bug#6674: PATCH: fix assignment of grep-find-use-xargs on Windows

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 01 Aug 2010 22:03:29 -0600
> From: Christoph <cschol2112@googlemail.com>
> CC: bug-gnu-emacs@gnu.org
> 
> On 8/1/2010 9:10 PM, Eli Zaretskii wrote:
> 
> > No.  That's because the DOS port doesn't call command.com at all.  It
> > has its own implementation of a shell as part of the `system' function
> > in the standard library it links against.  That implementation
> > supports pipes, redirection, quoting, long (up to 16KB) command lines,
> > and a few other minor Posix features, like /dev/null.
> 
> I see. Just out of curiosity, why can't this shell implementation be 
> used for Windows?

(Looks like the original bug is fixed already, but I will answer this
anyway, for the record.)

Yes, we could do that.  The source of the DJGPP implementation used by
the DOS port is Free Software.  However, this is a non-trivial job,
because porting that code to Windows will need some reimplementation.
E.g., pipes are implemented with temporary files and commands are run
sequentially, one by one (this is DOS, right?), but on Windows we have
real pipes and we should run both sides of the pipe concurrently.