[CMake] How do you handle recursive dependencies in CMake

[Raymond Wan]

Hi,


On Tue, Jun 28, 2016 at 8:41 PM, Cfyz <cfyzium at gmail.com> wrote:
> dependencies' locations. Personally I do not agree with that as I see
> neither any way around specifying paths to dependencies not any substantial
> harm in that. Maybe I am missing something but as far as I've found there
> was not discussion about this matter before.


Actually, there has been discussions about transitive dependencies
before.  In fact, such discussions crop up once a month or two.

See for example,
http://public.kitware.com/pipermail/cmake/2016-January/062590.html
(which I did reply, also with a link to my GitHub repository with a
minimal example).  Perhaps many others before me have also done the
same.  [Again, just because I reply doesn't mean I think I'm
right...I'm learning through discussions, as well!]

In my humble opinion, Sven's problem is two-fold.  They are
inter-related, but they could be separated.  The first is the
transitive dependency and for this, if it's all within the same source
code tree then something like what I did could work.  The second is
that the dependencies are not installed in system-level directories,
even though multiple users on a super-computer need to share them.

Because of this second factor, I don't have an idea what Sven should
do.  Indeed, what you suggest could work -- as I don't have a need, I
haven't given that much thought.

I think if I were presented with the same problem as Sven, I'd ask the
system administrator to install it.  Or, if that wasn't possible, use
ExternalProject.  Yes, if there are 100 users, then there would be 100
copies of the dependency.  But, running CMake will grab the most
recent copy from the source repository.  It's inefficient in terms of
disk space, but at least A (assuming A depends on B) will be built
correctly.  I don't know if CMake's aim is to build software correctly
*and* save disk space...  :-)

Ray