[CMake] CMake Digest, Vol 74, Issue 62

[Carlos Lopez Gonzalez]

>On Fri, 18 Jun 2010 10:40:46 +0200 Michael Hertling wrote:

>On 06/17/2010 11:29 AM, Carlos Lopez Gonzalez wrote:
>> Hi,
>> I'm new to cmake and want to port a C++ project which is now built using autotools to cmake build system.
>> The project has some libraries (we call them modules) which are used in two applications. The applications uses lt_dladdsearchdir to add the path where to search the modules and >then uses the lt_dlopenext and lt_dlsym to register the modules.
>> When using cmake, do I need to use ltdl as well or will cmake replace the way the libraries are found and registered?
>
>If your project's libraries are actually to be loaded dynamically at
>the behest of the applications, i.e. "dlopened", you further need a
>library to achieve this as it is a runtime affair and, thus, beyond
>CMake's scope, so stay with libltdl or switch to the simpler libdl,
>e.g., if you want to get rid of the libtool stuff. In either case,
>you should build dlopened libraries with ADD_LIBRARY(...MODULE...)
>in order to prevent other binaries to link against them explicitly.
>
>If your libraries don't need to be dlopened - your question somewhat
>seems to be targeted on this - you should build them as ordinary shared
>libraries with ADD_LIBRARY(...SHARED...) and link other binaries against
>them with TARGET_LINK_LIBRARIES(), so the runtime linker automatically
>takes care to load them when the applications are launched. To ensure
>they are found after being installed at a perhaps unusual location,
>look at CMake's RPATH support, e.g.:
>
><http://www.cmake.org/Wiki/CMake_RPATH_handling>
>
>'hope that helps.
>
>Regards,
>
>Michael


Hi Michael, now it makes much more sense. For whom has curiosity the project in particular is Synfig (http://synfig.org)
Synfig is a a2D vector animation program and it has layers, importers and exporters. In Synfig, layers, importers and exporters
instances are created based on a "book" of layers, importers or exporters. The program reads from file or from the user interaction 
what's the layer it needs to create based on the layer's name, what's the exporter it needs to create based on the extension of the file to 
export or what's the importer to instantiate based on the extension of the file which is being imported. So each "module" (layer, importer
or exporter) is never called directly (like any other library) by the class name but by a "factory" (a pointer to the constructor) that is stored
at the start up of the application in a book (std:map) of modules. So in one way or other, the application needs to know the pointer to the 
module before it is needed, so that's the reason for use libltdl. 
Thanks for pointing me to libld which I'll take a look. 
In any case, the ADD_LIBRARY are needed, right?

Thanks 

Carlos López