[CMake] Handling dependencies between projects

[Raymond Wan]

Dear all,

I know this is a frequent question on this mailing list, but I'm being
a bit overwhelmed with information and not too sure which direction I
should head.

Basically, I have executables X and Y who are each top-level projects.
They make use of library A.  Library A in turn makes use of library B.
Both A and B are libraries which are linked to, but they are also
executables -- I compile with a temporary main () function in order to
do some tests.  That is, their CMakeLists.txt generate both a library
and an executable.

So, the dependencies are like this:

X <-- A <-- B
Y <-- A <-- B

What I'm confused about are:

1)  Should all 4 have their own Project () lines?

2)  Should X and Y have ExternalProject () lines to A?

3)  Should A have ExternalProject () lines to B?

4)  Or maybe instead of ExternalProject (), I should use Add_Subdirectory ()?

5)  Or should X and Y have Target_Include_Directories () to A; should
A have a Target_Include_Directories () to B?

...or maybe something else?

What I think is that they should all have their own Project ().  And
perhaps A and B should have Install () lines that install libraries
into ${CMAKE_INSTALL_PREFIX}/lib/ and header files to
${CMAKE_INSTALL_PREFIX}/include/.  Then, X, Y, and A needs
Target_Include_Directories () to this path and *NOT* the where the
source code of A and B reside.

All this removes ExternalProject () from the picture...  It's true
what I'm including is mine but these libraries could be used
separately by other programs (i.e., Y).

I hope this is clear -- there are just too many options and the
documentation is thorough but the difference between each seems small.
At least too small for me to distinguish...

Thank you!

Ray