Re: More problems with `make -n' in automake-generated rules.

[Ralf Wildenhues]

* Stefano Lattarini wrote on Wed, Nov 03, 2010 at 06:48:16PM CET:
> Hello Ralf.  Again, just a couple of nits w.r.t. the test cases...

Thanks; but I didn't mean to actually commit the second patch
(just in case that wasn't clear).

That said, I'll reply to your comments inline.

> On Monday 01 November 2010, Ralf Wildenhues wrote:
> > --- /dev/null
> > +++ b/tests/remakedry.test
> > @@ -0,0 +1,82 @@

> > +# Make sure GNU `make -n' doesn't trigger file updates when Makefile
> > +# is out of date.
> > +
> > +# The subdir rebuilding rules rely on GNU make automatically updating
> > +# the makefile and its prerequisites (through am--refresh).
> > +required=GNUmake
> Why requiring GNU make here?  After all, if a make implementation does not
> implement automatic Makefile-rebuild rules, it should trivially pass this
> test, and if implements them, it makes sense to run this test on it too.

But that requires me to think about the test again: was this really
meant to test portable code?  The rebuilding rules, esp. the am--refresh
trick, rely on GNU make-specifics, and special-casing some test of it
just because it may or may not happen to trigger the specifics doesn't
seem robust.  I don't want the next small patch to this test cause a
failure for non-GNU make, a failure I'm really not interested in in this
test.

Does that make sense?

> > +cat > Makefile.am <<'END'
> > +SUBDIRS = sub
> > +END
> > +mkdir sub
> > +: > sub/Makefile.am
> > +
> > +$ACLOCAL
> > +$AUTOMAKE
> > +$AUTOCONF
> > +./configure
> > +$MAKE
> > +
> > +# The toplevel rule is not problematic, as it is not recursive.
> > +$sleep
> > +touch Makefile.in
> > +$sleep
> Is this second sleep really needed?  More instances below.

Definitely is.  I want Makefile to be strictly newer so that ls -1t
is guaranteed to work not because of locale ordering but because of
different time stamps.

> > +$MAKE -n Makefile
> > +test `ls -1t Makefile Makefile.in | sed 1q` = Makefile.in
> Waht about using here the `is_newest' function provided by `tests/defs'?

That would be a viable alternative that would also allow to ditch the
second sleep, I guess (untested).

> > +# Go through contortions to avoid GNU make's first, internal "rebuild 
> > Makefile
> > +# even in dry mode" cycle in the recursive (am--refresh) part.
> > +(cd sub && $MAKE -n Makefile AM_MAKEFLAGS="-n Makefile")
> I'd add a "|| Exit 1" here, just to be sure w.r.t. shells with buggy `set -e'.

What bug would you be trying to work around with it?

> One more intance below.
> > +test `ls -1t sub/Makefile config.status | sed 1q` = config.status
> > +(cd sub && $MAKE Makefile)
> > +test `ls -1t sub/Makefile config.status | sed 1q` = sub/Makefile
> > +
> > +: 

Cheers,
Ralf