[CMake] A few newbie "how to" questions

[Simon Perreault]

Hello,

I'm using CMake for building the source code of a research project where a few 
people of diverse level of technicality will contribute. It will have to be 
buildable in Visual Studio as well as under Linux.

I have a few simple questions on how to do stuff with CMake. Hopefully someone 
can donate a few minutes and answer at least one of them. ;) Thanks in 
advance. (I've done my homework: I read the documentation many times, as well 
as the FAQ and the wiki.)

1. A few files require the Matlab libraries and include. This package is 
installed in varied and unpredictable places, and therefore I chose to force 
the user to specify the MATLABROOT variable manually. I used the following 
code:

IF (NOT DEFINED MATLABROOT)
    MESSAGE(FATAL_ERROR "Please define the MATLABROOT variable.")
ENDIF (NOT DEFINED MATLABROOT)

Then I run cmake with "cmake -DMATLABROOT=/path/to/matlab ." and it works. 
However, if I do "touch CMakeLists.txt; make" it fails, requiring me to 
specify MATLABROOT once again instead of fetching it from the cache. What is 
the correct way to do this?

2. Is it possible to have per-sourcefile definitions? i.e. In one directory I 
have a few .c files which require the MATLAB_MEX_FILE definition while others 
are stand-alone programs that don't need it. ADD_DEFINITIONS seems to have a 
global effect.

3. Same question as 2 but concerning INCLUDE_DIRECTORIES.

4 and 5. Same questions as 2 and 3, but this time I want per-library or 
per-executable instead of per-sourcefile.

That's it for now. I'll probably have more as I continue writing this new 
build system.