Re: Moving creation of libtool/ltmain.sh to config.status

[Tim Van Holder]

> I am still unconvinced though.  It is config.status job to
> generate files,
> and automake (and make) would work better if config.status performed the
> generation.

Yes, but the main problem is that tags are appended to libtool, so
you can't have some stock libtool.in that is transformed.  The patch
I posted used two new build files, that are combined with ltmain.sh to
form libtool using an AC_CONFIG_COMMAND; the other option is to build
a libtool.in and let an AC_CONFIG_FILE transform it into libtool, but
that requires AC_SUBST'ing a lot of variables (and as I've found out,
the tag system isn't currently set up to properly cache each tag's version
of the config vars, making this tricky.

> This too would be improved by performing libtool generation in
> config.status, the way it works now is pretty much a horrible hack.

Agreed, but the fact that you append to libtool itself makes this hard.
I suppose we could distribute a 'libtool.in' instead of ltmain.sh; that
would basically be the default config vars (using @var@) followed by
ltmain.sh as it exists now.  libtool.m4 could then strip any tag configs
from this file during setup, and run as it does now, appending tag configs
as appropriate (also using @var_TAG@).  Then autoconf could simply use
its AC_SUBST machinery to create libtool.
The libtool distribution would have a libtool.bootstrap or something,
which corresponds to the current ltmain.in, that would have the package
and timestamp substituted in at bootstrap time (and in the Makefile) to
get libtool.in.

Note: I am notorious for missing elegant solutions to problems, so there
are quite likely some better solutions.

> Autoconf-2.50 has lots of nice new machinery to make generation of project
> specific files in config.status easy to achieve.

True, but libtool is pretty special.  Of course, we could just wrap
libtool.m4 in a giant AC_CONFIG_COMMANDS and have config.status (try to)
do all of the libtool configuring.  But since autoconf isn't set up for
such (ab)use, I expect this will be non-trivial as well.

> Does autoconf-2.50 or higher have a way to schedule macroised
> code to run in config.status, so that we could write a libtool.m4 macro
> to save configure time libtool script based link tests until after
> libtool has been built?

You can use AC_CONFIG_COMMANDS to run any kind of commands in config.status,
but most of the support variables aren't present in config.status (unless
you explicitly emit them), and you can't AC_SUBST or AC_DEFINE inside
config.status (as those affect how config.status is generated), making it
pretty much useless for link tests.