cmake: Selecting a generator within CMakeLists.txt

Question

I would like to force CMake to use the "Unix Makefiles" generator from within CMakeLists.txt.

This is the command I use now.

cmake -G "Unix Makefiles" . 

I would like it to be this.

cmake . 

When running on windows with VC installed and a custom tool-chain.

I would expect to be-able to set the generator in the CMakeLists.txt file.

Maybe something like this.

set(CMAKE_GENERATOR "Unix Makefiles") 

Answer 1

Here is what worked for me - create a file called PreLoad.cmake in your project dir containing this:

set (CMAKE_GENERATOR "Unix Makefiles" CACHE INTERNAL "" FORCE)

Answer 2

It seems to me that the variable CMAKE_GENERATOR is set too late if set in the CMakeLists.txt. If you use (even at the beginning of CMakeLists.txt)

set(CMAKE_GENERATOR "Ninja") message("generator is set to ${CMAKE_GENERATOR}") 

you can see in the output something like

% cmake ../source -- The C compiler identification is GNU 4.9.2 ... -- Detecting CXX compile features - done generator is set to Ninja -- Configuring done -- Generating done -- Build files have been written to: /tmp/build 

So the variable is only set at the very end of the generation procedure. If you use something like

set(CMAKE_GENERATOR "Ninja" CACHE INTERNAL "" FORCE) 

in CMakeLists.txt, then in the very first run of cmake ../source (without -G) the default generator is used. The variable CMAKE_GENERATOR is stored in the cache, though. So if you rerun cmake ../source afterwards, it will use the generator as specified in the CMAKE_GENERATOR variable in the cache.

This is surely not the most elegant solution, though ;-) Maybe use a batch file that will actually execute the cmake -G generator for the user...