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Re: running with -jN on Windows

From: Eli Zaretskii
Subject: Re: running with -jN on Windows
Date: Tue, 03 Jan 2006 20:22:26 +0200

> Date: Tue, 3 Jan 2006 03:11:46 -0500
> Cc: Alessandro Vesely <address@hidden>, address@hidden
> From: "Paul D. Smith" <address@hidden>
>   ez> Yes, but what feature of cmd.exe do we need for -j, and why?  I
>   ez> need to know this in order to understand the problem and the
>   ez> solution, and in order to test the patched Make.
>   ez> KJKHyperion says we need the caret-escaping, but it's not clear to me
>   ez> at all why this would allow -j.
> The critical thing that is needed from the shell to allow -jN to work is
> that it can be invoked with open file descriptors (a pipe in this case)
> and that it can further pass those open file descriptors to programs it
> invokes, unmolested.

That is the default behavior on Windows (and, as a matter of fact,
even on DOS).  It was never any other way, because this part of file
handling was copied from Unix back when MS-DOS v2 first introduced
decent file I/O.

> As far as I know that's all you need from the shell to get -jN working.

Why ``from the shell''? is it because the shell might sometimes be
used for command invocation (the ``slow'' method)? or for some other
reasons, which are valid in the ``fast'' method as well?

Anyway, if file handle inheritance is the only requirement on Posix
systems that allows -jN, then the proposed patch does nothing in this
area on Windows.  I guess it is dealing with some Windows-specific
aspect of Make, perhaps the invocation via batch files.  I will have
to dig into this when I have another slot of free time.

Thanks for the explanations.

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