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Re: Parallel Make

From: Ken Smith
Subject: Re: Parallel Make
Date: Thu, 01 Apr 2004 10:52:53 -0500
User-agent: Mozilla Thunderbird 0.5 (Windows/20040212)

I'm not convinced that build systems would break if -j without arguments suddenly meant nothing instead of infinitely parallel. The build would run serially but it would proceed correctly. In my environment -j without arguments is invariably not what we want so if this doesn't get changed in gmake itself, I will end up patching it locally anyway. I just hoped that others saw this as a flaw with -j and that it would be easy enough to fix.

However, that part of the discussion was an aside and my real concern is that I was actually giving an argument to -j which was ignored. It is not always ignored but in 10 builds it was ignored 5 times. When "-j 4" is the first argument on the command line it never happens. When it appears after a variable assignment it happens occasionally. Any ideas?


Tristan Van Berkom wrote:

Noel Yap wrote:

I agree that a lone -j shouldn't default to infinity for practical reasons. OTOH, a default of 1 would make the flag meaningless and a default of 2 seems unclean to me. IMHO, -j shouldn't have a default at all. Further, for those that like the infinite behaviour, I think allowing --jobs=infinity would help curb such an appetite a little.

    Hmmm, the same could be said about the unix open system call; why
should i have to open a named pipe in read/write if I dont want to block ?
why not throw non-blocking behavior on as default and add a O_BLOCK flag
instead ?

Ok, so its a bad example; but what I'm getting at is that you cant just
modify the expected behavior of the open() system call because everyone's
code will instantly break, much in the same way as IMO, many build
systems will break when you change the expected behavior of GNU make.

If everyone is bent on changing that behavior, why not add something new
like `-J' which behaves exactly like `-j' but with a different default
behavior ?

My casual too sence ;-)


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