Re: source dependencies cleanup?

Matthias Urlichs (smurf@noris.de)
5 Dec 1996 00:22:36 +0100

In linux.dev.kernel, article <199612040008.AAA00373@oboe.it.uc3m.es>,
"Peter T. Breuer" <ptb@oboe.it.uc3m.es> writes:
>
> > Not a major pain as the kernel takes a while to compile on this machine
> > anyway but I believe (after a quick perusal of the .depend files) that
> > mkdep is fast mainly because it skips stuff.
>
> Absolutely wrong (i.e. "that turns out not to be the case" :). It is

Sorry, but Linus' mkdep _does_ skip stuff.

Assume that a1.c and a2.c both include b.h which in turn includes c.h.

GCC -M output would be
a1.o: a1.c b.h c.h
a2.o: a1.c b.h c.h

Linus' mkdep instead depends on being executed on the heders too:
a1.o: a1.c b.h
a2.o: a1.c b.h
b.h: c.h
touch b.h

This all works out perfectly well. Well... almost. The big advantage of the
latter is that you scan b.h only once; gcc scans it twice. The big
disadvantage is that you can't keep your kernel sources on a readonly
partition.

-- 
It were not best that we should all think alike; it is the difference
of opinion that makes horse races.

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