SCCS and make (was Help with SCCS)

[Robert Hartman]

In article <570003 at hpsemc.HP.COM> bd at hpsemc.HP.COM (bob desinger) writes:
>Rit Chiang (chiang at m2c.ORG) writes:
>> 1) Since SCCS would not let you do hierarchy, is there anything out
>> there that can traverse the tree structure of SCCS directories.  I have
>> implemented a recursive csh script that would take any SCCS commands
>> and traverse down the tree.  However, I have noticed the performance
>> is awful.
>
>The csh may be dragging you down ...

Another approach is to use make in a recursive fashion, in conjunction
with SCCS.  A very simplistic example would be a program that depends
on a library which is maintained in a separate subdirectory.  Perhaps
that library, in turn, also depends on objects from a lower-level library.

The topmost makefile, ./Makefile, would invoke a make command to
(re)build the library, say `liba.a', but in the `liba' directory.
That nested make command would be run in liba, and use the makefile
there to build the library.  The liba makefile would also contain a
nested make command, to build the lower-level library, say
`libb.a', in liba/libb.  Finally, the makefile in liba/libb would
contain instructions for building libb.a.

Each makefile would also contain a rule for building .c files from the 
corresponding s.file.  Since .o files can be built using suffix rules, there
is no need to specify rules for them.  -bob.

========== ./Makefile ============

prog: prog.o liba.a
	cc -o prog  x.o liba.a

prog.o: prog.c  # show that prog.o depends on prog.c, so prog.c gets built 

prog.c: SCCS/s.prog.c
	-sccs get -s prog.c

liba.a: liba/liba.a
	-ln liba/liba.a liba.a

liba/liba.a: FORCE
	-cd liba ; make liba.a

FORCE:	# hack to force the nested make to run, even though liba/liba.a exists
	# if it's up to date wrt its sources in liba, the nested make will 
	# simply return.

========== liba/Makefile ============

liba.a: x.o y.o z.o libb.a
	-mkdir tmp
	-cd tmp ; ar xv ..libb.a # extract objects from libb.a in tmp
	-cp x.o y.o z.o tmp      # copy local objects to tmp
	-cd tmp ; ar rv liba.a ; mv liba.a .. # collate all objects into liba.a
	-rm -rf tmp

x.o y.o z.o: $$(@:.o=.c) # fancy footwork to show that ?.o depends on ?.c

x.c y.c z.c: SCCS/s.$$@  # fancy footwork to show ?.c depends on SCCS/s.?.c
	-sccs get -s $@

libb.a: libb/libb.a
	-ln liba/liba.a liba.a

libb/libb.a: FORCE
	-cd libb ; make libb.a
FORCE:
======================================