[CMake] Portable preprocessor defines?

[Bill Hoffman]

Robert Dailey wrote:
> Hi,
> 
> I want to define a preprocessor directive through CMakeLists.txt, 
> however the only documented method of doing this that I see is 
> *add_definitions()*. Is there a better way of doing this? According to 
> the documentation this isn't 100% portable, which in my opinion defeats 
> the entire purpose of using CMake to begin with (Or at the very least 
> that function itself). I don't think it is right to have to specify -D. 
> I should be able to do:
> 
> add_definitions( BOOST_ALL_NO_LIB )
> 
> However, I have to do:
> 
> add_definitions( -DBOOST_ALL_NO_LIB )
> 
> Any help would be greatly appreciated.
> 
> 
We have yet to find a compiler that does not support -D.  However, it 
seems unportable.  In cmake 2.6 we added properties on directories and 
targets that do not have the -D:

http://www.cmake.org/cmake/help/cmake2.6docs.html#prop_dir:COMPILE_DEFINITIONS
http://www.cmake.org/cmake/help/cmake2.6docs.html#prop_tgt:COMPILE_DEFINITIONS

That said, in doing that cmake parses add_definitions for -D and turns 
it into one of those properties anyway.  So, both are equally compiler 
portable at this point should we ever see a compiler that does not use -D...

-Bill