Re: conditionally disabling libltdl subconfigure

[Bob Friesenhahn]

On Wed, 22 Aug 2012, Brice Goglin wrote:

> Hello,
>
> I am working at embedding libltdl inside our project (hwloc, an Open MPI
> subprojet). Our plugins are not expected to be enabled in the most
> common cases. So I am trying to see if the libltdl sub-configure could
> be skipped entirely unless really needed (when plugins are enabled, and
> libltdl is indeed built). I got the usual failure when I tried to put
> LTDL_INIT inside a conditional block so I am looking for something else now.

While it does not accomplish exactly what you are looking for, the 
GraphicsMagick project (as an example) successfully uses the 
nonrecursive option so that the configure bits needed to configure 
libltdl are included into the primary configure script.  The libltdl 
configuration then vastly less expensive since it just adds a few more 
tests and not a whole configure script and whole new Makefile.in. 
This approach causes the combined configure script to include some 
libltld-specific configuration options.  It is good that these options 
are offered by the top-level configure since they will then appear in 
configure --help and the user is not left to guess about options which 
might be useful for subordinate configures.

This is in configure.ac:

LTDL_INIT([convenience nonrecursive])

and this in Makefile.am

include libltdl/Makefile.inc

where Makefile.inc is a makefile fragment from libltdl.

The project can then choose not to request to build libltdl even 
though it was configured.

Bob
--
Bob Friesenhahn
address@hidden, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/