Create relocatable package with proper autogenerated config cmake

Question

I have created cmake target, say A, and want to install it and create a Config file, so that the installed package could be relocatable. My code is:

install(EXPORT ${PROJECT_NAME}Targets
    FILE ${PROJECT_NAME}Targets.cmake
    NAMESPACE ${PROJECT_NAME}::
    DESTINATION ??? )

Here, I am having a problem with the proper destination. I want the Config file to be installed where ${CMAKE_INSTALL_PREFIX} points to. But when I put ${CMAKE_INSTALL_PREFIX} at ???, my resulting ATargets.cmake file contains the line:

set(_IMPORT_PREFIX "C:/Libraries/...")

which is the actual value of ${CMAKE_INSTALL_PREFIX}. This _IMPORT_PREFIX is later prepended to the parameters of set_target_properties() command inside the auto-generated ATargets.cmake, resulting in hard coded paths, valid only on the installation system.

I tried to use some generator expressions like <$IMPORT_PREFIX> in place of ???, but this gave me an error at cmake generation. I also tried to omit DESTINATION which in my opinion should place the file in the location relative to ${CMAKE_INSTALL_PREFIX}, but cmake complained about it too.

Can you please help me with this issue?

Package files generated by CMake are not intended to be relocatable. You may create relocatable package by writing "config" file by yourself. — Tsyvarev, Aug 17 '17 at 09:27
@Tsyvarev: well, according to the cmake docs: ```Packages created by install(EXPORT) are designed to be relocatable``` (source: https://cmake.org/cmake/help/v3.8/manual/cmake-packages.7.html) — Piotr G, Aug 17 '17 at 09:30
Hmm, not sure what they mean by "relocatable". However, you may try `.` (dot) or `./` as DESTINATION option for install files precisely under installation prefix. Such paths should be treated as relative by CMake, so "relocation" wouldn't suffer. — Tsyvarev, Aug 17 '17 at 09:42
Ok. That helped a litte. I don't have absolute paths any longer. Unfortunately, there is still problem in the generated Target.cmake: to produce the _IMPORT_PREFIX it strips the filename component twice instead of once: ```get_filename_component(_IMPORT_PREFIX "${CMAKE_CURRENT_LIST_FILE}" PATH) get_filename_component(_IMPORT_PREFIX "${_IMPORT_PREFIX}" PATH)```. The paths produced in this way are still invalid. — Piotr G, Aug 17 '17 at 11:34

Bruce Adams · Answer 1 · 2019-05-17T16:07:19.583

This is an old question so you have probably solved it already (or given up).

I think the critical thing is that the export DESTINATION matches the one given to INSTALL_DESTINATION to configure_package_config_file().

what we are using is:

  install(TARGETS
    foobar
    EXPORT foobarLibTargets
    LIBRARY DESTINATION lib)
  set(ConfigFileInstallDir lib/cmake/foobar)
  set(INCLUDE_INSTALL_DIR include)
  set(LIBRARY_INSTALL_DIR lib)
  configure_package_config_file(src/main/cmake/foobarConfig.cmake.in
    "${CMAKE_CURRENT_BINARY_DIR}/foobarConfig.cmake"
    INSTALL_DESTINATION "${ConfigFileInstallDir}"
    PATH_VARS INCLUDE_INSTALL_DIR LIBRARY_INSTALL_DIR)
  write_basic_package_version_file(
    "${CMAKE_CURRENT_BINARY_DIR}/foobarConfigVersion.cmake"
    VERSION "${VERSION}"
    COMPATIBILITY ExactVersion)
  export(EXPORT foobarLibTargets
    FILE "${CMAKE_CURRENT_BINARY_DIR}/foobarLibTargets.cmake")
  install(EXPORT foobarLibTargets
    FILE foobarLibTargets.cmake
    DESTINATION "${ConfigFileInstallDir}")
  install(FILES
    "${CMAKE_CURRENT_BINARY_DIR}/foobarConfig.cmake"
    "${CMAKE_CURRENT_BINARY_DIR}/foobarConfigVersion.cmake"
    "${CMAKE_CURRENT_BINARY_DIR}/foobarLibTargets.cmake"
    DESTINATION "${ConfigFileInstallDir}")

${ConfigFileInstallDir} is replaced automagically by _IMPORT_PREFIX so that the generated foobarLibTargets.cmake contains something like:

set_property(TARGET foobar APPEND PROPERTY IMPORTED_CONFIGURATIONS RELEASE)
set_target_properties(foobar PROPERTIES
  IMPORTED_LOCATION_RELEASE "${_IMPORT_PREFIX}/lib/foobar.so.2.0.0"
  IMPORTED_SONAME_RELEASE "libfoobar.so.2"
)

There can be troubles getting this to work. See my questions:

See you in the ward for those suffering from cmake related nervous disorders in the near future...

Create relocatable package with proper autogenerated config cmake

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