Re: Fix makedepend depmode to cope with VPATH builds

[Ralf Wildenhues]

Hi Stefano,

* Stefano Lattarini wrote on Sat, Apr 09, 2011 at 11:38:47AM CEST:
> On Friday 08 April 2011, Ralf Wildenhues wrote:
> > * Stefano Lattarini wrote on Fri, Apr 08, 2011 at 01:05:53PM CEST:
> > > On Wednesday 06 April 2011, Ralf Wildenhues wrote:

> > > > +  # makedepend may prepend the VPATH from the source file name to the 
> > > > object.
> > > > +  sed_object_re=`echo $object | sed 's/[].[^$\\*|]/\\\\&/g'`
> > > >
> > > A couple of questions/observations about the sed command:
> > >  1. I wasn't sure whether `.', `$', `^' and `*' are to be escaped when 
> > > used in
> > >     a bracket expression; however, the POSIX standard at:
> > >       <http://pubs.opengroup.org/onlinepubs/007908799/xbd/re.html>
> > >     says they shouldn't be.  Also, I couldn't find any reference in the
> > >     Autoconf manual pointing to a sed implementation that doesn't respect
> > >     this part of the standard.
> > 
> > Ah, cool.  Then I recon we don't need this escaping step at all.
> >
> Why not?  The sed command below:
>   sed "s|^.*\($sed_object_re *:\)|\1|" "$tmpdepfile" > "$depfile"
> doesn't use any bracket, does it?

I'm not sure I understand the question.  Can you rephrase it?

> > The only character I was worried about was $, as it can occur in
> > object names now and then (ok, mostly java, and that doesn't use
> > depcomp).  Any others in the list are pretty much excluded anyway,
> > because they will evoke shell expansion errors when used in a
> > makefile unquoted.  Except for '.', but I'm not afraid of matching
> > a bit too broadly here, the final 'o' will take care that we don't
> > match any header files.
> >
> OK, this makes sense (even if I'd err on the safe side w.r.t. the `.'
> character),

OK, can you come up with a practical example (i.e., a valid object file
name) where we would match something wrongly here?  Remember the input
file only contains lines of the form
  $object: header header...
  $object: header \
   header header...

While somebody might arguably name their header foo.o, I do think they
deserve what they get.

> but I don't see how it's related to my observation above.
> What am I missing?

I guess then I don't understand your observation then.  Your observation
tells me that object file names of the form foo^bar.o and foo$baz.o are
not problematic.  I observe that no one in their right mind names their
object foo[bar.o or foo]bar.o or foo\bar.o (see the various instspc*
tests for why they would not work in practice anyway).  So I conclude
that it is not needed to do regex-escaping for the object file name.

> > @@ -503,7 +503,8 @@ makedepend)
> >    touch "$tmpdepfile"
> >    ${MAKEDEPEND-makedepend} -o"$obj_suffix" -f"$tmpdepfile" "$@"
> >    rm -f "$depfile"
> > -  cat < "$tmpdepfile" > "$depfile"
> > +  # makedepend may prepend the VPATH from the source file name to the 
> > object.
> >
> I'd add a comment here telling why there's no need to escape $object for the
> sed commmand just below.

I will, after I've understood your remaining comments.

Thanks,
Ralf