踩坑日志：CMAKE里的ADD_SUBDIRECTORIES要在INCLUDE_DIRECTORIES后面

背景：

我想include一个第三方库。我已经把库放到third_party这个文件夹里了，也在CMakeLists里设置了INCLUDE_DIRECTORIES(${PROJECT_SOURCE_DIR}/third_party)。但是编译器死活找不到这个库。

错误：

project(LabelAndStore)
cmake_minimum_required(VERSION 2.8)
 
SET(CMAKE_CONFIGURATION_TYPES Debug)

SET(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/lib)
SET(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/lib)
SET(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/bin)

ADD_SUBDIRECTORY(src)

INCLUDE_DIRECTORIES(${PROJECT_SOURCE_DIR}/third_party)

正确：

project(LabelAndStore)
cmake_minimum_required(VERSION 2.8)
 
SET(CMAKE_CONFIGURATION_TYPES Debug)

INCLUDE_DIRECTORIES(${PROJECT_SOURCE_DIR}/third_party)

SET(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/lib)
SET(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/lib)
SET(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${PROJECT_SOURCE_DIR}/bin)

ADD_SUBDIRECTORY(src)

总结：

ADD_SUBDIRECTORIES要在INCLUDE_DIRECTORIES后面。或者说，在ADD_EXECUTABLE之前要先INCLUDE_DIRECTORIES。