On Sat, 2 Feb 2008, Felix Fietkau wrote:
> Robert P. J. Day wrote:
> > i'm just following the logic for the simple clean targets, and i'm
> > confused as to how "make clean" and "make dirclean" work. in a
> > fully-cleaned openwrt tree, running either of those dumps one into
> > "make menuconfig", which would seem to be a pointless exercise if the
> > tree is already clean.
> clean and dirclean are dependent on the target selection, thus depend on
> the .config file.
>
> > so i can see that either of those targets requires a rebuild of
> > .config if it isn't already there, which strikes me as weird.
> >
> > i'm also puzzled by that second rule and its command:
> >
> > @$(MAKE) $@
> >
> > i'm sure i'm just missing something, but doesn't that just reinvoke
> > its own target? how *does* that work? thanks for any enlightenment.
> It works like this: When a build system target is called, the OPENWRT_BUILD
> variable is unset and that means, the preparatory work is to be done first.
> Package directories are scanned, prerequisites are checked, the .config is
> checked for if the target requests it, etc.
> At this point, the variable OPENWRT_BUILD is exported and when a real
> target is called, @$(MAKE) $@ will call the Makefile again, but because of
> the different set of variables, the real build system logic is included now
> and thus provides access to the real targets.
> Hope this helps.
sorry, i probably sounded a bit dense when i first asked that
question. i'm actually familiar with two-pass makefiles, i just
didn't understand that exact rule command:
@$(MAKE) $@
since $@ does, of course, simply refer to the target of that very
rule, which seemed pointlessly recursive. but now i'm assuming that
the variable $(MAKE) expands to more than just a simple "make"
invocation -- i'm guessing it has to include a change directory of
some kind, right? *then* it would make perfect sense.
rday
--
========================================================================
Robert P. J. Day
Linux Consulting, Training and Annoying Kernel Pedantry
Waterloo, Ontario, CANADA
Home page: http://crashcourse.ca
Fedora Cookbook: http://crashcourse.ca/wiki/index.php/Fedora_Cookbook
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