CMake教程9：cocos2d-x的CMake逻辑分析

1. CMake起点：cocos2d-x/CMakeLists.txt

# 设置module的查找目录
set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${PROJECT_SOURCE_DIR}/cmake/Modules/")
include(BuildModules)
# 调用过程
BuildModules()

2. 设置lib：cmake/Modules/BuildModules.cmake

# 设置lib变量... 
# xxhash
if(USE_PREBUILT_LIBS OR USE_SOURCES_EXTERNAL)
  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/external/xxhash)
  # 设置_INCLUDE_DIRS、_LIBRARIES等变量
  set(XXHASH_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/external/xxhash)
  set(XXHASH_LIBRARIES xxhash)
else()
  cocos_find_package(xxhash xxhash REQUIRED)
endif()
# 开始真正的项目lib添加
add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/cocos)

3. 将lib引入到项目中：cocos2d-x/cocos/CMakeLists.txt

# 引入lib
foreach(pkg XXHASH ... )
  cocos_use_pkg(cocos2dInternal ${pkg})
endforeach()

4. cocos_use_pkg的实现在cmake/Modules/CocosBuildHelper.cmake

function(cocos_use_pkg target pkg)
    set(prefix ${pkg})
    
    set(_include_dirs  ${${prefix}_INCLUDE_DIRS})
    # 将头文件目录加入到项目中
    include_directories( ${_include_dirs} )

    set(_library_dirs ${${prefix}_LIBRARY_DIRS})   
    # 将库文件目录加入到项目中
    link_directories(${_library_dirs})

    set(_libs ${${prefix}_LIBRARIES})
    # 链接lib
    target_link_libraries(${target} ${_libs})
 
    # 宏定义
    set(_defs ${${prefix}_DEFINITIONS})
    add_definitions(${_defs})
endfunction()

与第2步设置_INCLUDE_DIRS、_LIBRARIES等变量前后呼应。