How do I iterate over all CMake targets programmatically?

Question

Is there a way to get all targets of a CMake project from within the top level CMakeLists.txt, i.e. iterate over the targets programmatically?

The reason I

Answer 1

Improving Florian answer, BUILDSYSTEM_TARGETS is a not really a global property but a directory scoped one. A request for enhancement is currently open to request a truly global property. Using SUBDIRECTORIES property it's possible retrieve recursively all targets in the scope of the current directory with the following function:

function(get_all_targets var)
    set(targets)
    get_all_targets_recursive(targets ${CMAKE_CURRENT_SOURCE_DIR})
    set(${var} ${targets} PARENT_SCOPE)
endfunction()

macro(get_all_targets_recursive targets dir)
    get_property(subdirectories DIRECTORY ${dir} PROPERTY SUBDIRECTORIES)
    foreach(subdir ${subdirectories})
        get_all_targets_recursive(${targets} ${subdir})
    endforeach()

    get_property(current_targets DIRECTORY ${dir} PROPERTY BUILDSYSTEM_TARGETS)
    list(APPEND ${targets} ${current_targets})
endmacro()

get_all_targets(all_targets)
message("All targets: ${all_targets}")