make -b does what?

[Michael Meissner]

In article <23 at ctbilbo.UUCP> ray at ctbilbo.UUCP (Ray Ward) writes:

| In article <1990Feb22.042021.4936 at phri.nyu.edu> roy at phri.nyu.edu (Roy Smith) writes:
| >lois at hpfcdc.HP.COM (Lois Gerber) writes:
| >> This question is directed at OLD (and I mean OLD) Unix gurus :
| >> Can anyone explain to me clearly what the -b option is for in make?
| >	Beats the hell out of me.  I can't even find make in my (6th
| >edition) Unix manual at all.  Did I get a defective manual?
| 
| I would suspect the -b came in somewhere around System III.  Steve Talbott's
| _Managing Projects with Make_ ( O'Reilly and Assoc. 1-800-338-NUTS )
| describes the option:
| 
|    The -b option is, in most implementations, on by default.  It
|    assures backward compatibility with earlier versions of _make_,
|    so that old description files continue to work.
| 
| I have no idea what the old description file format differences were.

In practice, -b serves another use.  If you have recursive makefiles,
you usually use (on System V) something like:

	dir/foo: dir/foo.c
		cd dir; $(MAKE) -$(MAKEFLAGS) foo

If no arguments were passed to the toplevel make, then the recursive
make would get a plain "-", which means that the Makefile is passed
via standard input.  Since -b is implicitly set, it is passed on to
the recursive make.
--
Michael Meissner	email: meissner at osf.org		phone: 617-621-8861
Open Software Foundation, 11 Cambridge Center, Cambridge, MA

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