Re: AC_CONFIG_SUBDIRS

[Bob Rossi]

On Wed, Dec 06, 2006 at 08:06:54PM +0100, Ralf Wildenhues wrote:
> Hello Bob,
> 
> * Bob Rossi wrote on Wed, Dec 06, 2006 at 03:40:00PM CET:
> > 
> > When you run the top-level configure script, it determines what libraries 
> > you 
> > need to build the project, and then downloads the .tar.gz dependency, untars
> > it, and configures it. Currently I ./configure the sub projects manually by
> > calling the sub projects ./configure directly. However, using 
> > AC_CONFIG_SUBDIRS 
> > might be better, because I think it'll pass down the top-level configure 
> > options 
> > to the subproject.
> 
> Right.  It assumes some things though: for example, that you may want to
> share the cache file between the two configure runs.  This is not
> practical, for example, if one but not both packages are to be cross
> compiled (e.g., because you need a compiler for both $host and $build).
> 
> > I'm wondering if there is a way to get AC_CONFIG_SUBDIRS to work, even
> > though the configure script or sub directory isn't available until
> > ./configure is run and it determines what libraries to download. 
> 
> This should already work out of the box.  If the file $sub/configure is
> present at the time it should be run (at the end of configuring), then
> it will be run.

OK, something must be wrong with my setup then. I'll look into it.

> > I'm wondering how options are passed down through AC_CONFIG_SUBDIRS from
> > the top-level Makefile. Can you tweak the options for each sub project?
> 
> No.  This is currently one of the biggest limitations of this macro.
> I'd be happy if we could come up with another macro for sub-configure
> scripts that would allow for more freedom.  Primary issues are:
> - What and how can we allow the user to specify what is passed/mangled/
>   not passed?  This is trickier than it seems: package authors typically
>   cannot know which option an end-user would like to be passed down.
> - When should cache file sharing be turned off?
> 
> Some other technical details come to mind as well.
> 
> This could help eliminate the number of mostly-buggy hand-written bits
> that several package use, in the long term.
> 
> If you embark upon writing a private macro for yourself, please start
> from a recent copy of Autoconf's and modify that.  Older versions have
> had more quoting quirks.

OK, I don't have time to do this now. However I am interested in the
functionality.  Maybe sometime in the future ...

Thanks,
Bob Rossi