C语言中find_package()的搜索路径的实现

set(CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake_module)

set(OpenCV_ROOT "/usr/lib/opencv_249/build") #可在子目录查找
#为了在这里查找.cmake文件
set(OpenCV_DIR "/usr/lib/opencv_300/build")  #弱智，不能在子目录查找

find_package(OpenCV REQUIRED
          NO_MODULE        # tells CMake to use config mode
          NO_DEFAULT_PATH) # and don't look other anywhere
 #此时用的在${OpenCV}查找的.cmake文件

#find_package就是这么实现的
#头文件目录(是个目录的绝对路径)
find_path(<NAME_INCLUDE_DIRS> NAMES XX.h PATHS /usr/include /usr\local/include/ ...)
#库文件(是个文件的绝对路径)
find_library(<NAME_LIBRARIES> NAMES lib-name PATHS /usr/lib /usr/local/lib ...)

set(CMAKE_INCLUDE_PATH /usr/local/include/opencv
                    /usr/include)
 
find_path(CV_INCLUDE_DIRS NAMES cv.h PATHS CMAKE_INCLUDE_PATH)

#find opencv lib
find_package(OpenCV REQUIRED
              NO_MODULE # should be optional, tells CMake to use config mode
              PATHS /usr/local # look here
              NO_DEFAULT_PATH) # and don't look anywhere else