Re: Multidirectory libraries make

[Paul Smith]

Hi; please don't send your message multiple times to the list.

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On Wed, 2012-06-20 at 10:45 -0700, icegood wrote:
> Paul Smith-20 wrote:
> > 
> > I don't understand why you have $(sublibraries) as targets.  Just make
> > the rule to build the actual library invoke the sub-make:
> > 
> > all: $(currlib) 
> > $(real_sublibraries) :
> >         $(MAKE) "--directory=$(dir $@)" -f makefile.mak
> > $(currlib) : $(obj) $(real_sublibraries)
> >         ar -cqs $@ $(obj) 2>/dev/null
> > 
> > Untested obviously.
> > 
> > 
> It tested and tested for a couple of years :) With targeting of
> real_sublibraries you'll obtain make that will build not all time namely
> when bar depends on obj in F(bar) directory - foo doesn't know about such
> change. It's just compares date of libbar.a with own one and decides do
> nothing! While dependance on  $(sublibraries) works well.
> The key is $(sublibraries) is .PHONY depended.
> On other hand if i simply would do $(real_sublibraries)  to be  .PHONY
> depended then foo will rebuild always.

OK, then you're trying to cheat at declaring dependencies.  If
$(currlib) depends on some object in a different directory bar, then it
should depend on THAT (that is, the "obj" variable should contain the
path to that object file) and not depend on the library in bar.

Then make the directories order-only prerequisites:

        .PHONY: $(sublibraries)
        $(sublibraries) : 
               $(MAKE) "--directory=$@" -f makefile.mak
        
        $(currlib) : $(obj) | $(sublibraries)
                ar -cqs $@ $(obj) 2>/dev/null

Now all the sublibraries rules will be done before $(currlib) is built,
but it won't cause $(currlib) to be rebuilt.