Re: Patch for autoconf/145

[Ralf Corsepius]

Pavel Roskin wrote:
> 
> Hello, Derek!
> 
> > > Two possible solutions:
> > >
> > > 1) VPATH = ${srcdir}
> > >
> > > 2) VPATH = @srcdir@
> 
> I'm now strongly for the later. Minor implementation problems in Autoconf
> cannot justify a possible behavior change for the users.
> 
> Unfortunately, a trivial AC_SUBST([SET_VPATH], [VPATH = @address@hidden) 
> doesn't
> work - Autoconf actually makes a great effort to protect the second
> argument from expanding.
> 
> > I remember reading in an obscure comment in some code somewhere that 
> > @srcdir@
> > was preferable to $(srcdir) for optimization reasons.  i.e. Make would
> > otherwise try and consult $(srcdir) every time it needed to know the value 
> > of
> > VPATH (possibly several times per target) and _we_ know it's not going to
> > change.
> 
> Ok, that just confirms my previous statement.
> 
FWIW: I vaguely recall that some make's VPATH must not contain any
make- nor shell-variable (It could have been earlier gmakes or
Solaris' make but I am not sure).

> > Unfortunately, ignoring this still leaves us with the original reason for 
> > the
> > magic.  That reason is that the user may want to add paths to VPATH and this
> > doesn't necessarily mean shooting herself in the foot.  As long as she 
> > leaves
> > @srcdir@ in there, everything Automake & Autoconf depended on for building 
> > out
> > of tree should still work, but Autoconf doesn't know in advance whether the
> > user did this or not.  

How about allowing @top_srcdir@ in VPATHs? IMHO, this would be more
handy than @srcdir@ if _really_ exploiting VPATH for building.

Ralf

-- 
Ralf Corsepius 
Forschungsinstitut fuer Anwendungsorientierte Wissensverarbeitung
(FAW)
Helmholtzstr. 16, 89081 Ulm, Germany     Tel: +49/731/501-8690
mailto:address@hidden           FAX: +49/731/501-999  
http://www.faw.uni-ulm.de