CODEWITHSUNDEEP
cmake
J. Doe
J. Doe

Reputation: 702

Simple find_package config file example

Now I have a lib I made my self that I want to use in another CMake c++ project. It exists in my computer like this.

${MY_LIB_PATH}\include
${MY_LIB_PATH}\lib\x86\debug\lib-files
${MY_LIB_PATH}\lib\x86\release\lib-files
${MY_LIB_PATH}\lib\x64\debug\lib-files
${MY_LIB_PATH}\lib\x64\release\lib-files

What would a basic config file be like which makes CMake find_package know those? I expected it would be very simple because it just doesn't have much information to provide. But this page just make my head hurt.

Sorry, I decided to copy the source code around so I don't really know which answer should be accepted.

Upvotes: 25

Views: 35406

Answers (3)

Marco Pantaleoni
Marco Pantaleoni

Reputation: 2539

Maybe this older doc could be a tad more lightweight. And there is also this tutorial or this other one. The last one is perhaps the simplest.

Hope to not have added more pain :-)

Following the docs should give something roughly like the following (supposing your library is mylib):

MyLib/MyLibConfig.cmake.in

# - Config file for the MyLib package
# It defines the following variables
#  MYLIB_INCLUDE_DIRS - include directories for MyLib
#  MYLIB_LIBRARIES    - libraries to link against
#  MYLIB_EXECUTABLE   - the bar executable

# Compute paths
get_filename_component(MYLIB_CMAKE_DIR "${CMAKE_CURRENT_LIST_FILE}" PATH)
set(MYLIB_INCLUDE_DIRS "@CONF_INCLUDE_DIRS@")

# Our library dependencies (contains definitions for IMPORTED targets)
if(NOT TARGET mylib AND NOT MyLib_BINARY_DIR)
  include("${MYLIB_CMAKE_DIR}/MyLibTargets.cmake")
endif()

# These are IMPORTED targets created by MyLibTargets.cmake
set(MYLIB_LIBRARIES mylib)

MyLib/MyLibConfigVersion.cmake.in

set(PACKAGE_VERSION "@MYLIB_VERSION@")

# Check whether the requested PACKAGE_FIND_VERSION is compatible
if("${PACKAGE_VERSION}" VERSION_LESS "${PACKAGE_FIND_VERSION}")
  set(PACKAGE_VERSION_COMPATIBLE FALSE)
else()
  set(PACKAGE_VERSION_COMPATIBLE TRUE)
  if ("${PACKAGE_VERSION}" VERSION_EQUAL "${PACKAGE_FIND_VERSION}")
    set(PACKAGE_VERSION_EXACT TRUE)
  endif()
endif()

main MyLib/CMakeLists.txt

...

set(MYLIB_MAJOR_VERSION 0)
set(MYLIB_MINOR_VERSION 1)
set(MYLIB_PATCH_VERSION 0)
set(MYLIB_VERSION
  ${MYLIB_MAJOR_VERSION}.${MYLIB_MINOR_VERSION}.${MYLIB_PATCH_VERSION})

...

add_library(mylib SHARED mylib.c ...)

...

install(TARGETS mylib
  # IMPORTANT: Add the mylib library to the "export-set"
  EXPORT MyLibTargets
  RUNTIME DESTINATION "${INSTALL_BIN_DIR}" COMPONENT bin
  LIBRARY DESTINATION "${INSTALL_LIB_DIR}" COMPONENT shlib
  PUBLIC_HEADER DESTINATION "${INSTALL_INCLUDE_DIR}/mylib"
    COMPONENT dev)

...

# The interesting stuff goes here
# ===============================

# Add all targets to the build-tree export set
export(TARGETS mylib
  FILE "${PROJECT_BINARY_DIR}/MyLibTargets.cmake")

# Export the package for use from the build-tree
# (this registers the build-tree with a global CMake-registry)
export(PACKAGE MyLib)

# Create the MyLibConfig.cmake and MyLibConfigVersion files
file(RELATIVE_PATH REL_INCLUDE_DIR "${INSTALL_CMAKE_DIR}"
   "${INSTALL_INCLUDE_DIR}")
# ... for the build tree
set(CONF_INCLUDE_DIRS "${PROJECT_SOURCE_DIR}" "${PROJECT_BINARY_DIR}")
configure_file(MyLibConfig.cmake.in
  "${PROJECT_BINARY_DIR}/MyLibConfig.cmake" @ONLY)
# ... for the install tree
set(CONF_INCLUDE_DIRS "\${MYLIB_CMAKE_DIR}/${REL_INCLUDE_DIR}")
configure_file(MyLibConfig.cmake.in
  "${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/MyLibConfig.cmake" @ONLY)
# ... for both
configure_file(MyLibConfigVersion.cmake.in
  "${PROJECT_BINARY_DIR}/MyLibConfigVersion.cmake" @ONLY)

# Install the MyLibConfig.cmake and MyLibConfigVersion.cmake
install(FILES
  "${PROJECT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/MyLibConfig.cmake"
  "${PROJECT_BINARY_DIR}/MyLibConfigVersion.cmake"
  DESTINATION "${INSTALL_CMAKE_DIR}" COMPONENT dev)

# Install the export set for use with the install-tree
install(EXPORT MyLibTargets DESTINATION
  "${INSTALL_CMAKE_DIR}" COMPONENT dev)

Upvotes: 4

Stephen Newell
Stephen Newell

Reputation: 7828

Don't write a config yourself; use CMake's export command. It's too broad to cover here in its entirety, but here's a modified example from one of my projects:

install(TARGETS
        your_target
    EXPORT YourPackageConfig
    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
    LIBRARY DESTINATION ${CMAKE_INSTALL_LIBDIR}
    RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR}
)
export(TARGETS
        your_target
    NAMESPACE YourPackage::
    FILE "${CMAKE_CURRENT_BINARY_DIR}/YourPackageConfig.cmake"
)
install(EXPORT
        YourPackageConfig
    DESTINATION "${CMAKE_INSTALL_DATADIR}/YourPackage/cmake"
    NAMESPACE YourPackage::
)

This will create the config file for you, so other projects can use it via find_package.

find_package(YourPackage REQUIRED)
target_link_libraries(foo YouprPackage::your_target)

This handles the IMPORTED targets automatically, and also lets you embed compiler flags, include paths, library dependencies, and even which files are part of your interface (basically, anything that falls under the INTERFACE properties).

Upvotes: 35

WinCloud
WinCloud

Reputation: 193

Put a "${libname}-config.cmake" in library's root.

Then add an IMPORTED target in that file.

There is a example for libprotobuf.

add_library(libprotobuf STATIC IMPORTED GLOBAL)

set_target_properties(libprotobuf PROPERTIES 
    IMPORTED_LOCATION "${CMAKE_CURRENT_SOURCE_DIR}/prebuilt/android/${ANDROID_ABI}/libprotobuf.a"
    IMPORTED_LINK_INTERFACE_LIBRARIES "${ZLIB_LIBRARIES};${CMAKE_THREAD_LIBS_INIT}"
    INTERFACE_INCLUDE_DIRECTORIES "${CMAKE_CURRENT_SOURCE_DIR}/src")

Set Env or CMake variable "${libname}_DIR" to "${MY_LIB_PATH}"

Use it.

find_package(${libname})
#.......
target_link_libraries(main ${libname})

Upvotes: 8

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