Re: LIBTOOL_DEPS wrong when AC_CANONICAL_BUILD not called before initializing libtool

[Ralf Wildenhues]

Hello Jakub,

* Jakub Bogusz wrote on Fri, Mar 14, 2008 at 08:18:55PM CET:
> On Fri, Mar 14, 2008 at 07:53:13PM +0100, Jakub Bogusz wrote:
> > Reduced test:
> > 
> > #v+
> > AC_INIT([libtool-test], [0])
> > 
> > if test "$with_canonical" != ""; then
> >         AC_CANONICAL_HOST
> > fi
> > 
> > AC_LIBTOOL_WIN32_DLL
> > AC_PROG_LIBTOOL
> > 
> > echo "NM: $NM"
> > echo "OBJDUMP: $OBJDUMP"
> > #v-

Thanks, but the above is a problem that cannot be solved with current
Autoconf.  The issue is that an AC_REQUIRE'ment is met by any previously
expanded macro, autoconf cannot see the fact that AC_CANONICAL_HOST was
expanded inside a shell conditional.

The way to avoid this is to simply not put AC_CANONICAL_HOST inside a
shell conditional in the first place.  If the original problematic code
you had used some other macro there instead, which itself AC_REQUIRE'd
AC_CANONICAL_HOST, then the way to solve that setup is to use

  AS_IF([test $some_conditional],
        [MACRO_THAT_REQUIRES_AC_CANONICAL_HOST])

because in that case (with Autoconf 2.61+), AC_CANONICAL_HOST will be
expanded outside (before) the if statement.  For more information, you
can e.g. read this thread
<http://thread.gmane.org/gmane.comp.sysutils.autoconf.general/10187/focus=10188>
and the one referenced in that message, and the doc pointers given
there.

> And I've just found another problem related to AC_CANONICAL_BUILD placed
> to late (or ltmain= substitution too early). For this one cross compiler
> is not needed. Just add one more line at the end of the above configure.ac:
> 
> echo "LIBTOOL_DEPS: $LIBTOOL_DEPS"
> 
> then regenerate configure.
> 
> `./configure` output ends with:
> LIBTOOL_DEPS: /ltmain.sh
> 
> `./configure --with-canonical` output ends with:
> LIBTOOL_DEPS: ./ltmain.sh
> 
> Note the missing "." in the first case. It's because of empty ac_aux_dir
> (used for ltmain substitution in configure) which is set by one of
> AC_CONFIG_AUX_DIR* macros, with default one called from
> AC_CANONICAL_BUILD.

That's really still the same issue, with the undocumented Autoconf macro
AC_CONFIG_AUX_DIR_DEFAULT.

Cheers,
Ralf