How to tell cmake to generate different default targets for out-of-source-builds?

Question

How can I write a CMakeLists.txt file that accepts different out-of-source builds? I'm not talking about Debug and Release, but more about something like one build for remote testing one for local testing, etc.

For example: If I go into the build_local build directory and run make I want to have the sources compiled for local configration. If I run make in the build_production build directory I want to compile the sources using a different configuration. I understand that out of source builds are what I need. I just don't quite understand how to:

1. tell cmake what kind of configuration to generate (e.g., cd build_local; cmake -D local?)
2. how to write a CMakeLists.txt file in a way that it generates different default target (i.e. make all or make) depending on the configuration

Has someone an example or a link to appropriate documentation?

Thanks!

Answer 1

Using if command you can fill default target(and others) with different meanings, dependent of configuration.

CMakeLists.txt:

...
option(LOCAL "Build local-testing project" OFF)
if(LOCAL)
    add_executable(program_local local.c)
else()
    add_executable(program_remote remote.c)
endif()

local build:

cd build_local
cmake -DLOCAL=ON ..
make
...

remote build:

cd build_remote
cmake ..
make

In if branches you can use even different add_subdirectory() commands, so your configured project may completely differ for different configurations.