[CMake] Proper way to export a library

[David Cole]

> Microsoft believed in hidden by default for shared libraries.

Don't say things like this: people will never hide anything ever 
again... ;-)

But seriously, making only those things public that are explicitly 
exported has some major benefits: for one, it minimizes the probability 
of clashes when combining multiple independent components.

It really should be a software developer's rule of thumb / best 
practice to have the minimal set of symbols necessary be exported. 
Anything exported that does not need to be is a maintenance burden, a 
learning curve hurdle for newbies, and increases the likelihood of name 
clashes with other libraries: all bad things.

So minimize your public APIs and your exports.


2 cents worth,
D