background

In many cases, compiling a project requires linking to a third-party library. In this case, you need to know the following information about the third-party library:

• .h header file address
• Dynamic library .so or static library .a file address
• The name of the linked library

Common library

Some commonly used libraries will provide oneFindXXXX.cmakeFile, at this point we only need to use the following command (log4cppFor example)

# Add REQUIRED parameter to indicate that this is a required dependency library
find_package(LOG4CPP REQUIRED)
include_directories(${LOG4CPP_INCLUDE_DIR})

Directory Structure

In order to be able to wrap multiple Finder, you need to organize the following directory structure to add related modules later.

├── CMakeLists.txt
│   ├── cmake
│ │ ├── modules # to store FindXXXX.cmake
│   │   │   └── FindLOG4CPP.cmake
│   │   └── toolschain
 │ │ └── Tiny4412.cmake # for storing toolschain.cmake

Add the modules path to the top level CMakeLists.txt

set(CMAKE_MODULE_PATH 
    APPEND "${CMAKE_SOURCE_DIR}/cmake/modules/"
    )

Unusual library

Sometimes, some libraries do not provide CMake module files, or usemakefileTo compile, you need to write the Finder, build./cmake/modules/A directory to hold the Finder used by this project. Top layerCMakeLists.txtAdd the following command

set(CMAKE_MODULE_PATH 
    APPEND "${CMAKE_SOURCE_DIR}/cmake/modules/"
    )

(still using log4cpp as an example) to create a nameFindLOG4CPP.cmakeThe contents of the file are as follows

# - Find Log4cpp
# Find the native LOG4CPP includes and library
#
#  LOG4CPP_INCLUDE_DIRS - where to find LOG4CPP.h, etc.
#  LOG4CPP_LIBRARIES   - List of libraries when using LOG4CPP.
#  LOG4CPP_FOUND       - True if LOG4CPP found.

 # Determine if log4cpp is already included
if (LOG4CPP_INCLUDE_DIR)
  set(LOG4CPP_FIND_QUIETLY TRUE)
endif ()

 # Find header file location
 # PATH_SUFFIXES Path suffix, normal installation of log4cpp is located in the system path /log4cpp/ folder
find_path(LOG4CPP_INCLUDE_DIR
  NAMES Category.hh
     # You can manually create a search path by using the following command:
  # PATHS /usr/local/include
  PATH_SUFFIXES log4cpp
  DOC "Log4cpp include directories"
)

 # Find library file location
find_library(LOG4CPP_LIBRARY
  NAMES log4cpp
  DOC "Log4cpp library"
)

 # Assign a value to the relevant variable when both the header file location and the library file location are found
if (LOG4CPP_INCLUDE_DIR AND LOG4CPP_LIBRARY)
  set(LOG4CPP_FOUND TRUE)
  set(LOG4CPP_LIBRARIES ${LOG4CPP_LIBRARY})
  set(LOG4CPP_INCLUDE_DIRS ${LOG4CPP_INCLUDE_DIR})
else ()
  set(LOG4CPP_FOUND FALSE)
  message(WARNING "LOG4CPP not found")
endif ()

 # Print some error messages
if (LOG4CPP_FOUND)
  if (NOT LOG4CPP_FIND_QUIETLY)
    message(STATUS "Found LOG4CPP: ${LOG4CPP_LIBRARIES}")
  endif ()
else ()
  if (LOG4CPP_FIND_REQUIRED)
    message(STATUS "Looked for LOG4CPP libraries named ${LOG4CPPS_NAMES}.")
    message(FATAL_ERROR "Could NOT find LOG4CPP library")
  endif ()
endif ()

 # This option is not very understandable, it seems to be used for cmake gui
mark_as_advanced(
  LOG4CPP_LIBRARIES
  LOG4CPP_INCLUDE_DIRS
)

link

At this point, you only need to write the relevant variables in the way of the common library.include_directoriesYes, link when generating the executable

add_executable(test test.cc)
target_link_libraries(test ${LOG4CPP_LIBRARIES})