CMake: write executables to multiple subdirectories - cmake

Question

I have a source and build tree that looks something like this:
+-build/
+-bin/
+-modules/
+-src/
+-tests/
+-test1/
+-test2/
I have also configured CMake to write the executables into the build/bindirectory. That all works fine.
What I would like is to have most of my executables written into the build/bin directory, while those built from sources under the test directories be written into a build/bin/tests directory.
Is this possible? Can someone point me in the right direction?
I've tried setting the RUNTIME_OUTPUT_DIRECTORY variable directly and I've tried using set_target_properties, but without success.
Ideally, I like to be able to set something in the CMakeLists.txt file in the tests directory and have it trickle down into the subdirectories.

Answer 1

You may set CMAKE_RUNTIME_OUTPUT_DIRECTORY variable as many times as you want. Each setting will affect only on the executables created since that setting until the next one.
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
# Futher executables will be placed under 'bin/'
add_executable(my_program <sources>...)
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin/tests)
# Futher executables will be placed under 'bin/tests/' instead
add_executable(test1 <sources>...)
add_executable(test2 <sources>...)
If you are creating the tests in the separate CMakeLists.txt, the settings can be made modular:
CMakeLists.txt:
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
# Futher executables will be placed under 'bin/'
add_executable(my_program <sources>...)
add_subdirectory(tests)
tests/CMakeLists.txt:
set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin/tests)
# Executables created below will be placed under 'bin/tests/' instead
add_executable(test1 <sources>...)
add_executable(test2 <sources>...)
Actually, when you call add_executable, it just uses the current value of the CMAKE_RUNTIME_OUTPUT_DIRECTORY variable. This fact can be found in the documentation about RUNTIME_OUTPUT_DIRECTORY target property, which is affected by the variable.