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Re: Non-recursive makefiles


From: Tom Tromey
Subject: Re: Non-recursive makefiles
Date: 28 May 2006 15:49:38 -0600
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.3.50

>>>>> "Ralf" == Ralf Corsepius <address@hidden> writes:

Ralf> An aspect, I don't see how an import feature would help is
Ralf> "scoping": A subdir-Makefile.am controls one subdir, a flat
Ralf> toplevel Makefile controls all subdirs. I.e. when developing on
Ralf> a package, with a non-flat Makefile structure, e.g. a "make
Ralf> clean" inside of a subdir cleans this single subdir. With a flat
Ralf> Makefile the whole source tree will be "cleaned".

FWIW the original 'import' plan included support for scoping of the
automake-generated rules, e.g. 'make subdir/clean'.

Ralf> Yet another aspect is size/speed of files generated from
Ralf> flat-Makefile.am. Processing all-flat Makefile.am of a source tree
Ralf> containing 100s of source-files can be annoyingly slow and easily reach
Ralf> the order of several minutes, even on contemporary HW.
Ralf> I don't see how an "import feature" would help.

The hope was that a single Makefile would improve performance by
eliminating multiple 'make' invocations, and by allowing better
parallelism across the entire project -- right now parallelism is
limited to a single directory.

We didn't really consider make scalability back when thinking about
this.  Oops.  But, perhaps whatever problems there are in make are
solvable there.

In any case the import plan looked pretty complicated to implement.
And, it would have required user support in some cases.  As you noted,
you can't go around rewriting make rules arbitrarily; we were thinking
of adding a new '%subdir' automake-time substitution, or something
like that, to let people write relocatable rules.

Tom




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