Re: [PATCH] {master} aclocal: deprecate ACLOCAL_AMFLAGS, trace AC_CONFIG_MACRO_DIR instead

[Ralf Corsepius]

On 07/03/2012 10:54 PM, Stefano Lattarini wrote:
> On 07/02/2012 02:57 PM, Stefano Lattarini wrote:
> > On 07/02/2012 02:26 PM, Ralf Corsepius wrote:
> > > On 06/30/2012 08:30 PM, Stefano Lattarini wrote:
> > > > Maintaining ACLOCAL_AMFLAGS in the Makefile.am to pass extra flags
> > > > to aclocal is (and have always been) quite of an hack.  For example,
> > > > autoreconf is forced to grep Makefile.am to honour those flags.  But
> > > > this is a bad obsolescent behaviour; in fact, the autotools have moved
> > > > consistently in the past years from custom grepping of Makefile.am and
> > > > configure.ac to tracing of m4 macro calls, which is more consistent,
> > > > more reliable and more flexible.
> > > >
> > > > And when autoreconf is not used, the developer is forced to add *by hand*
> > > > the flags specified by ACLOCAL_AMFLAGS to the aclocal calls not triggered
> > > > by make rebuild rules; here lie again more duplication and more chances
> > > > for errors.
> > > >
> > > > Moreover, ACLOCAL_AMFLAGS has only two typical use cases:
> > > >
> > > >     - to instruct aclocal to look for extra macro definition in a local
> > > >       directory (as with "ACLOCAL_AMFLAGS = -I m4"); and
> > > >
> > > >     - to further instruct aclocal to copy in that local directory the
> > > >       required third-party .m4 files found in the system-wide directory
> > > >       (as with "ACLOCAL_AMFLAGS = -I m4 --install").
> > > >
> > > > The first use case can be better covered if aclocal can instead trace and
> > > > honours call to the AC_CONFIG_MACRO_DIR autoconf macro; and the second
> > > > use case shouldn't be considered really legitimate, as it is quite (and
> > > > subtly) brittle (see automake bug#9037).
> > > ACLOCAL_AMFLAGS is able to take sequences of  "-I's".
> > >
> > > Will your AC_CONFIG_MACRO_DIR be able handle such cases?
> > No; and I think there is no compelling reason to support multiple local
> > m4 macro dirs in a build system setup.
Well, likely you don't have enough experience in using automake to have 
encountered such cases?

Classical use case is deep sourcetrees:

configure.ac
macros/
...
subdir/configure.ac
subdir/macros
subdir/macros/Makefile.am:
ACLOCAL_AMFLAGS = -I macros -I ../macros
...


> > But I recognize I might be proven wrong, so here's a sketch of how I
> > plan to proceed in this case.
> >
> > Once we start warning about ACLOCAL_AMFLAGS (in Automake 1.14), people
> > that were using multiple '-I' option there will see that the new semantics
> > don't support their setup anymore.  So they'll either adjust such setup,
> > or, if that turns out to be impossible, will write to bug-automake to
> > complain.  If their complain turns out to be legitimate, we will add a
> > new autoconf macro 'AM_EXTRA_LOCAL_M4_DIRS' (say), that aclocal will
> > trace and use to adjust its search path accordingly.
> I've now pushed this patch.
Please revert this change. IMO, this is yet annother case of you rushing 
out short-sighted silly changes, because you apparently lack sufficient 
user experience with the autotools to understand what you are doing.


Ralf