Re: CVS gettext: many test failures

[Bruno Haible]

Ralf Wildenhues wrote:
> > it creates the new files in the build
> > directory. I know the reason why: if a source distribution is installed in a
> > read-only location, the build in a VPATH should not touch any file in the
> > source directory.
> 
> That's not what I'd say.  You can only expect compiling from a read-only
> location to work right if that read-only location happens to contain up
> to date files.  If a bison input file is updated there, then one can
> rightly expect other files to need updated there as well.

Good! So please, can you fix automake to behave like this?

> > The result are inconsistent compiles, as you see.
> 
> I'm not trying to say that there isn't an Automake bug, but it uses an
> inference rule for .y.c, and the VPATH target lookup rules of GNU make
> (and other make implementations) are simply not simple:
> <http://www.gnu.org/software/autoconf/manual/html_node/Make-Target-Lookup.html>

The lookup rules are irrelevant here. The point is that automake generates
a rule that creates the po-gram-gen.c and po-gram-gen.h from po-gram-gen.y,
like this:

   .y.c:
          $(am__skipyacc) $(SHELL) $(YLWRAP) $< y.tab.c $@ y.tab.h $*.h 
y.output $*.output -- $(YACCCOMPILE)

and in the circumstances that
  - $(srcdir) != "."
  - po-gram-gen.y exists in $(srcdir) but not in "."
  - po-gram-gen.y has changed
  - po-gram-gen.c and po-gram-gen.h also exist in $(srcdir) but not in "."
    and are older than po-gram-gen.y
this rule will create _new_ files po-gram-gen.c and po-gram-gen.h in the
current directory. Some compiles will then use the po-gram-gen.h in the
current directory and some will use the po-gram-gen.h in $(srcdir).

The fix should be that in the cited circumstances po-gram-gen.c and
po-gram-gen.h should be updated in $(srcdir).

> How about this patch to force updates in srcdir?
> (Some BSD make cannot infer that file and $(srcdir)/file are
> the same target with VPATH = $(srcdir).)

This misses the point, because
  - we are not discussing BSD make here, but GNU make on a glibc system, and
  - a patch to gettext's Makefile.am will not affect the instantiations of
    automake's .y.c rule in other packages than gettext.

Bruno