Re: GNUmakefile covering sources in different directories

[Nicola Pero]

> >> OmniFoundation/GNUMakefile:
> >>   LIBRARY_NAME = OmniFoundation
> >>   LIBRARY_SUBPROJECTS = OpenStepExtensions FooDirectory
> >
> > B*llsh*t ... it should read, eg.
> >
> >   LIBRARY_NAME = OmniFoundation
> >   OmniFoundation_SUBPROJECTS = <subdirectory>
> 
> I thought, that would mean, that the subprojects are independant. I 
> mean, the subprojects need a project type, e. g. library. But they 
> shouldn't have a project type, just linked into the main project.
> And how do I link the object files to the main project afterwards?

To understand the issue, you need to make a clear difference between
'subprojects' and 'aggregate projects'.

subprojects are declared using xxx_SUBPROJECTS = ...

aggregate projects are declared using SUBPROJECTS = ...

(please take a couple of seconds to note the difference).  It is
unfortunate that aggregate projects are declared using SUBPROJECTS = ...,
which is confusingly similar to the variable used for subprojects.  This
is definitely confusing and is probably the cause of your confusion.  I
apologize for the bad naming, but it's historical.

Anyway, in this case Chris is explaining you about subprojects
(OmniFoundation_SUBPROJECTS = <list of subdirectories>), which is not the
same thing as aggregate projects (SUBPROJECTS = <list of subdirectories>).

Please note that subprojects are subprojects "of something".  As a matter
of fact, you declare them as for example in 

  Renaissance_SUBPROJECTS = AutoLayout Markup TagLibrary

So, AutoLayout, Markup and TagLibrary are "subprojects of Renaissance".  
(in the case of aggregate projects, aggregate projects are not bound to 
anything.  Eg,

  SUBPROJECTS = Source Documentation Tools

you see these are independent things, not belonging to anything, in fact,
aggregate projects are just independent projects hold in subdirectories,
while subprojects are parts of the a project hold in subdirectories).

In the case of subprojects, this means just that part of the files to
compile are held in the subdirectories.  Inside each subdirectory, you
should have a GNUmakefile for a project of type 'subproject'.  For 
example, in the AutoLayout directory of Renaissance, you could have 
something like -

include $(GNUSTEP_MAKEFILES)/common.make

SUBPROJECT_NAME = libgnustep-autolayout
libgnustep-autolayout_OBJC_FILES = \
 GSAutoLayoutDefaults.m \
 GSAutoLayoutManager.m \
 GSAutoLayoutStandardManager.m \
 GSAutoLayoutProportionalManager.m \
 GSHBox.m \
 GSVBox.m \
 GSHSpace.m \
 GSVSpace.m \
 NSViewSize.m

include $(GNUSTEP_MAKEFILES)/subproject.make

When you now type 'make' in the top directory (which is be a standard
project, such as a library in Renaissance's case), that will go into every
subproject's directory, compile the files there, and then automatically
link them into the main project's object file (you can do a similar thing
with headers, see eg Renaissance).

So, subprojects are a way to spread the parts of a project in
subdirectories.

An aggregate project (remember, this is defined by set up by using
SUBPROJECTS = ...) is different - in that case, the subdirectories contain
standalone / independent projects, each with its own well-defined type,
which are compiled independentely.  Aggregate projects effectively just
loop on the subdirectories and builds whatever is in there.  In this case,
you need to add SUBPROJECTS = ... to the top-level GNUmakefile, and
include aggregate.make.  The subdirs can hold any project type you wish.

Subprojects, which is what you are interested in in this case, instead
mean that a project has got some (or all) source files spread over a few
subdirectories.  The files are gathered, and linked into the main project
object file.  In this case, you need to add xxx_SUBPROJECTS = ... to the
top-level GNUmakefile.  The subdirs must hold stuff compiled using
subproject.make.