[cmake-developers] [Review Request] Topic CMakePackageConfigHelpers_build_tree

[Daniele E. Domenichelli]

On 21/07/14 14:23, Stephen Kelly wrote:
> Can you give a more-concrete example of what the problem is?


I have a project that is similar to this small example:


--- CMakeLists.txt

  cmake_minimum_required(VERSION 2.8.12)
  project(FOO NONE)
  set(FOO_VERSION 0.0.1)

  include(${CMAKE_CURRENT_LIST_DIR}/CMakePackageConfigHelpers.cmake)

  set(FOO_INSTALL_CMAKE_DIR "share/FOO/cmake")

  set(FOO_BUILD_ABSOLUTE_DIR "${CMAKE_BINARY_DIR}/share/FOO/absolute")
  set(FOO_INSTALL_ABSOLUTE_DIR "${CMAKE_INSTALL_PREFIX}/share/FOO/absolute")

  set(FOO_BUILD_RELATIVE_DIR "share/FOO/relative")
  set(FOO_INSTALL_RELATIVE_DIR "share/FOO/relative")

  #--------- BUILD TREE

  set(FOO_ABSOLUTE_DIR ${FOO_BUILD_ABSOLUTE_DIR})
  set(FOO_RELATIVE_DIR ${FOO_BUILD_RELATIVE_DIR})

  # FOOConfig.cmake (build tree)
  configure_package_config_file(FOOConfig.cmake.in "FOOConfig.cmake"
                                INSTALL_DESTINATION "${CMAKE_BINARY_DIR}"
                                PATH_VARS FOO_ABSOLUTE_DIR
                                          FOO_RELATIVE_DIR
                                NO_CHECK_REQUIRED_COMPONENTS_MACRO
                                BUILD_TREE)

  #--------- INSTALLED

  set(FOO_ABSOLUTE_DIR ${FOO_INSTALL_ABSOLUTE_DIR})
  set(FOO_RELATIVE_DIR ${FOO_INSTALL_RELATIVE_DIR})

  # FOOConfig.cmake (installed)
  configure_package_config_file(FOOConfig.cmake.in "FOOConfigInstall.cmake"
                                INSTALL_DESTINATION "${FOO_INSTALL_CMAKE_DIR}"
                                PATH_VARS FOO_ABSOLUTE_DIR
                                          FOO_RELATIVE_DIR
                                NO_CHECK_REQUIRED_COMPONENTS_MACRO)

  install(FILES ${CMAKE_BINARY_DIR}/${CMAKE_FILES_DIRECTORY}/FOOConfigInstall.cmake
          DESTINATION ${FOO_INSTALL_CMAKE_DIR}
          RENAME FOOConfig.cmake)

--- FOOConfig.cmake.in

  set(FOO_VERSION @FOO_VERSION@)

  @PACKAGE_INIT@

  set_and_check(FOO_ABSOLUTE_DIR "@PACKAGE_FOO_ABSOLUTE_DIR@")
  set_and_check(FOO_RELATIVE_DIR "@PACKAGE_FOO_RELATIVE_DIR@")



The project is supposed to work both from build tree (using
export(TARGETS)) and from the install tree (using install(EXPORT)).

The file FOOConfigInstall.cmake is perfect and can be relocated as
expected.

The file FOOConfig.cmake for the build tree contains

---
  [...]
  get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/../../../usr/local" ABSOLUTE)
  [...]
  set_and_check(FOO_ABSOLUTE_DIR "<absolute path to build directory>/share/FOO/absolute")
  set_and_check(FOO_RELATIVE_DIR "${PACKAGE_PREFIX_DIR}/share/FOO/relative")
---


in PACKAGE_PREFIX_DIR, obviously, the length list of "/.." depends on
the folder where the package is built. "/usr/local" is the prefix and it
makes no sense in the file for the build directory.

The path passed using a variable containing an _absolute path_ is
_correct_, but it uses the absolute path to the build directory.

The path passed using a variable containing a _relative path_ is _wrong_
and it contains a path relative to the install directory. If the package
was not installed this path is invalid.


This means that all the paths should be passed as absolute paths or the
generated file will be invalid.

With my patch applied and passing "BUILD_TREE" to the
configure_package_config_file call, the generated file becomes:

---
  [...]
  get_filename_component(PACKAGE_PREFIX_DIR "${CMAKE_CURRENT_LIST_DIR}/" ABSOLUTE)
  [...]
  set_and_check(FOO_ABSOLUTE_DIR "${PACKAGE_PREFIX_DIR}/share/FOO/absolute")
  set_and_check(FOO_RELATIVE_DIR "${PACKAGE_PREFIX_DIR}/share/FOO/relative")
---

This removes all the absolute paths from the file (This is not
necessary for using the package in the build tree, since I believe
that it's not going to be relocated, but I still think it is a good
thing), and very important, it allows you to pass relative paths
as PATH_VARS and get the same behaviour in both cases.



Cheers,
 Daniele