cmake链接MySQL分析

爱被打了一巴掌 2022-07-25 23:27 360阅读 0赞

下面这份代码，是我从网上找到的添加MySQL头文件和链接文件的CMake代码。

# - Find mysqlclient
    # Find the native MySQL includes and library
    #
    #  MYSQL_INCLUDE_DIR - where to find mysql.h, etc.
    #  MYSQL_LIBRARIES   - List of libraries when using MySQL.
    #  MYSQL_FOUND       - True if MySQL found.
    
    IF (MYSQL_INCLUDE_DIR)
      # Already in cache, be silent
      SET(MYSQL_FIND_QUIETLY TRUE)
    ENDIF (MYSQL_INCLUDE_DIR)
    #从下面那两个路径找mysql.h，将找到的路径放到MYSQL_INCLUDE_DIR这个变量中。
    FIND_PATH(MYSQL_INCLUDE_DIR mysql.h
      /usr/local/include/mysql
      /usr/include/mysql
    )
    #设置要寻找的链接库的名字，这里应该是找libmysqlclient.so
    SET(MYSQL_NAMES mysqlclient mysqlclient_r)
    #将libmysqlclient.so的路径放到MYSQL_LIBRARY
    FIND_LIBRARY(MYSQL_LIBRARY
      NAMES ${MYSQL_NAMES}
      PATHS /usr/lib /usr/local/lib
      PATH_SUFFIXES mysql
    )
    
    #如果上面找到mysql的头文件和mysql的库文件，就将MYSQL_FOUND设为真
    IF (MYSQL_INCLUDE_DIR AND MYSQL_LIBRARY)
      SET(MYSQL_FOUND TRUE)
      SET( MYSQL_LIBRARIES ${MYSQL_LIBRARY} )
    ELSE (MYSQL_INCLUDE_DIR AND MYSQL_LIBRARY)
      SET(MYSQL_FOUND FALSE)
      SET( MYSQL_LIBRARIES )
    ENDIF (MYSQL_INCLUDE_DIR AND MYSQL_LIBRARY)
    
    #如果找到并且没有设置QUIET，则输出搜到动态库路径
    #如果找不到就输出错误信息
    IF (MYSQL_FOUND)
      IF (NOT MYSQL_FIND_QUIETLY)
        MESSAGE(STATUS "Found MySQL: ${MYSQL_LIBRARY}")
      ENDIF (NOT MYSQL_FIND_QUIETLY)
    ELSE (MYSQL_FOUND)
      IF (MYSQL_FIND_REQUIRED)
        MESSAGE(STATUS "Looked for MySQL libraries named ${MYSQL_NAMES}.")
        MESSAGE(FATAL_ERROR "Could NOT find MySQL library")
      ENDIF (MYSQL_FIND_REQUIRED)
    ENDIF (MYSQL_FOUND)
    
    #将他标记为高级变量，具体什么作用没查到
    MARK_AS_ADVANCED(
      MYSQL_LIBRARY
      MYSQL_INCLUDE_DIR
      )

我们可以将这份代码写成一个cmake模块，然后通过FIND\_PACKAGE(< name>)去得到这个模块的头文件路径和链接库路径，得到的路径一般会存放在< name>\_LIBRARIES,< name>\_INCLUDE\_DIR这两个变量中。  
我可以将上面那份代码放到一个新的文件中FindMySQL.cmake,通过在主CMakeLists.txt中SET(CMAKE\_MODULE\_PATH dir)将其放入工程的某个目录中供工程使用，然后就可以调用FIND\_PACKAGE(MySQL)就可以得到mysql的头文件路径和动态链接库路径：MySQL\_INCLUDE\_DIR, MySQL\_LIBRARIES。