Re: kbuild 2.5 is ready for inclusion in the 2.5 kernel

Gerd Knorr
2002-05-03T12:10:12Z

Keith Owens wrote:
> On 3 May 2002 10:06:04 GMT,
> Gerd Knorr <kraxel@bytesex.org> wrote:
> >> Do it with NO_MAKEFILE_GEN=1 for much, much! faster builds.
> >
> >What exactly is the reason for this hack, i.e. why kbuild wants to
> >rebuild the Makefiles every time? Isn't it enougth to do that only
> >if .config has been touched?
>
> Or any of the Makefile.in files have changed.

.config + all Makefile.in's is still a small number of files where
make has to check the timestamp to see whenever a rebuild of the global
makefile is needed.

> Or any of the command line options have changed.

Which command line options?

> Or various environment variables have changed.
> Or the compiler has changed.

Which environment variables? CC / CFLAGS? Well, with other CFLAGS
and/or compiler you have to do a full rebuild anyway, thus using "make
clean" would work equally well ...

> Or a target file has been altered outside kbuild control.

Which is the users fault IMO. I don't see the point in trying to catch
this and make kbuild idiot proof. I doubt it is possible to make kbuild
clever enougth to handle all evil things a user could do. AI isn't that
good.

> Coding a special case to work out if the existing global makefile can
> be reused is horribly error prone.

Special case? I'd say it is the common case when doing kernel
development. At least I don't use another compiler for every second
make. I usually hack some piece of code and recompile the module then.

Gerd

--
You can't please everybody. And usually if you _try_ to please
everybody, the end result is one big mess.
-- Linus Torvalds, 2002-04-20