project(unitybuild_batchsize C) set(srcs "") foreach(s RANGE 1 8) set(src "${CMAKE_CURRENT_BINARY_DIR}/s${s}.c") file(WRITE "${src}" "int s${s}(void) { return 0; }\n") list(APPEND srcs "${src}") endforeach() add_library(tgt SHARED ${srcs}) set_target_properties(tgt PROPERTIES UNITY_BUILD ON UNITY_BUILD_BATCH_SIZE 4 )