
区分PROJECT_SOURCE_DIR, CMAKE_SOURCE_DIR,CMAKE_CURRENT_SOURCE_DIR
2.2 如果子目录的CMakeLists.txt没有使用project命令,则PROJECT_SOURCE_DIR等于上一层CMakeLists.txt的PROJECT_SOURCE_DIR。不论CMakeLists在根目录还是子目录,也不论CMakeLists.txt里面有没有调用project函数,CMAKE_SOURCE_DIR都等于根目录路径。1 根目录下的CMakeLists.txt的PROJECT_SOURCE_DIR等于根目录路径;sub2目录下的CMakeLists.txt。
