visual studio - How to detect if 64 bit MSVC with cmake?

Question

I have a project which uses cmake, one target is set to only build with MSVC:

 if (MSVC)
     add_library(test SHARED source.cpp) 
 endif()

Now the other issue is that this target is only designed for MSVC 32bit. So how can I detect that the generator is MSVC64 and skip this target?

Answer 1

The usual way to check if you're generating for a 64 bits architecture is to test CMAKE_SIZEOF_VOID_P:

project( ... )
...

# won't work before project()!    
if(CMAKE_SIZEOF_VOID_P EQUAL 8)
    # 64 bits
elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
    # 32 bits
endif()

This variable is only set after the project command!