🚀 go-pugleaf

I have a long list of filenames generated by the Make automatic variable $?
(all dependency files newer than the target) that I'd like to feed to a
depend file generator script. Unfortunately, on many (most? all?) System V
machines the space for environment variables and command line args is too
small.

We have three ways of generating this depend target, either link to a
production version (the fastest), perform an update of the local version
(medium fast), or create one from scratch (excruciatingly slow on machines
whose compiler doesn't understand "-M"). The actions for the depend target
look roughly like this (we use GNU make):

%.depend : GNUmakefile and lots of other files
	if [ we can link to the production version ] ; then \
	    ln -s $(production)/$@ $@ ; \
	elif [ $? is made up of just .c files ] ; then \
	    depend -u -f $@ $? ; \
	else \
	    depend -f $@ $(filter %.c,$^) ; \
	fi

Our System V machines sometimes give us "Arg list too long" errors on the
above command. The test arg in the elif branch and the two depend commands
can each have lots of files, thus combining to making the whole if statement
too long to execute (I think). Both of the individual depend commands are
short enough to run.

I'd like to use xargs to generate a series of depend update commands ("xargs
depend -u -f $@"), but I can't think of any way to generate stdin for xargs
that doesn't involve putting most or all of the $? contents on the command
line (using a series of echo commands or a for loop, for instance),
consequently generating an if statement that is too long.

Short of breaking up some of the libraries we build into smaller chunks
(which isn't really a viable option), can anybody see a way to get around
the small env/arglist space on System V machines for this problem?

Thanks,

--
Skip (montanaro@crd.ge.com)