multi-arch builds and recursive makes

[Robert P. J. Day]

  (sorry, i managed to lose paul's response to my original query, so i 
just grabbed the salient bits out of the list archives.)

Regarding Paul's essay on multi-arch builds, Paul wrote:

> The model is this: you run the make in the source directory.  That is
> sort of the "master" make.  It will invoke a sub-make in the target
> directory in order to build all the local targets.

> _BUT_, that sub-make doesn't try to build any subdirectories.  Instead,
> once the sub-make is done building the local targets it exits.  Then
> it's up to the parent make (in the source directory) to run any
> sub-makes.

> In short, you want to put any recursion into the section of the makefile
> that's invoked in the source directory, not the section invoked in the
> target directory.

ok, that makes a lot more sense -- i was trying to determine what tricky 
part of the solution made the recursive part work.

what this pretty clearly suggests is that, if you have a sizable project 
with numerous levels of subdirectories, you have to modify the makefile at 
every level in every subdirectory, and extend it to have the general 
structure:

 ifeq (,$(filter _%,$(notdir $(CURDIR))))
 include target.mk
 else
 #----- End Boilerplate

 VPATH = $(SRCDIR)

   Normal makefile rules here

 #----- Begin Boilerplate
 endif

right?  it just means that it will take time to convert an existing 
project from the regular build format to the multi-arch format, since you 
have to make that change throughout the software tree, correct?

rday