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Re: Improvement on parallel make

From: Christophe Lyon
Subject: Re: Improvement on parallel make
Date: Tue, 12 Dec 2006 14:00:13 +0100

> Maintaining the various levels of Makefiles of large projects can quickly
> become impracticable.

That's a general defect of recursive make setups.  How does .WAIT fix that?

> I try to advocate good Makefile writing, but I also try to avoid recursive
> Makefiles, and having a feature such as this .WAIT implementation would be
> quite handy.

To quote a coworker of mine: what problem are you trying to solve?

I have yet to see a problem here where .WAIT is obviously the right
solution.  It seems like a poor solution to the "no concurrency"
problem and unnecessary for the recursive make problems.
Well, the problem has already been detailed in the threads already mentionned.
If you consider a Makefile like:

all: all-subdir all-local
        # visit the subdirectories and run "make all" there

all-local: $(whatever local targets are)

The main thing I assume here may be that you "inherit" this Makefile from an external project, on which you may have little influence. You want to improve the build time but can't afford to re-write the whole set of Makefiles.
Let me rephrase it: your company wants you to work on a local variation of a large open source project. Most Makefiles are written as in the example above, where the assumption is that all-local will be built after all-subdir. If you can insert a .WAIT between the two, your problem is solved.
If you have to rewrite the whole stuff, you are likely to give up, depending on the complexity of the whole build system.


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