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  1. 20 Jan, 2011 2 commits
    • Brad King's avatar
      Modules: Include builtin FindPackageHandleStandardArgs directly · c4275592
      Brad King authored
      The FindPackageHandleStandardArgs module was originally created outside
      of CMake.  It was added for CMake 2.6.0 by commit e118a627 (add a macro
      FIND_PACKAGE_HANDLE_STANDARD_ARGS..., 2007-07-18).  However, it also
      proliferated into a number of other projects that at the time required
      only CMake 2.4 and thus could not depend on CMake to provide the module.
      CMake's own find modules started using the module in commit b5f656e0
      (use the new FIND_PACKAGE_HANDLE_STANDARD_ARGS in some of the FindXXX
      modules..., 2007-07-18).
      
      Then commit d358cf5c (add 2nd, more powerful mode to
      find_package_handle_standard_args, 2010-07-29) added a new feature to
      the interface of the module that was fully optional and backward
      compatible with all existing users of the module.  Later commit 5f183caa
      (FindZLIB: use the FPHSA version mode, 2010-08-04) and others shortly
      thereafter started using the new interface in CMake's own find modules.
      This change was also backward compatible because it was only an
      implementation detail within each module.
      
      Unforutnately these changes introduced a problem for projects that still
      have an old copy of FindPackageHandleStandardArgs in CMAKE_MODULE_PATH.
      When any such project uses one of CMake's builtin find modules the line
      
        include(FindPackageHandleStandardArgs)
      
      loads the copy from the project which does not have the new interface!
      Then the including find module tries to use the new interface with the
      old module and fails.
      
      Whether this breakage can be considered a backward incompatible change
      in CMake is debatable.  The situation is analagous to copying a standard
      library header from one version of a compiler into a project and then
      observing problems when the next version of the compiler reports errors
      in its other headers that depend on its new version of the original
      header.  Nevertheless it is a change to CMake that causes problems for
      projects that worked with previous versions.
      
      This problem was discovered during the 2.8.3 release candidate cycle.
      It is an instance of a more general problem with projects that provide
      their own versions of CMake modules when other CMake modules depend on
      them.  At the time we resolved this instance of the problem with commit
      b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake
      everywhere, 2010-09-28) for the 2.8.3 release.
      
      In order to address the more general problem we introduced policy
      CMP0017 in commit db44848f (Prefer files from CMAKE_ROOT when including
      from CMAKE_ROOT, 2010-11-17).  That change was followed by commit
      ce28737c (Remove usage of CMAKE_CURRENT_LIST_DIR now that we have
      CMP0017, 2010-12-20) which reverted the original workaround in favor of
      using the policy.  However, existing project releases do not set the
      policy behavior to NEW and therefore still exhibit the problem.
      
      We introduced in commit a364daf1 (Allow users to specify defaults for
      unset policies, 2011-01-03) an option for users to build existing
      projects by adding -DCMAKE_POLICY_DEFAULT_CMP0017=NEW to the command
      line.  Unfortunately this solution still does not allow such projects to
      build out of the box, and there is no good way to suggest the use of the
      new option.
      
      The only remaining solution to keep existing projects that exhibit this
      problem building is to restore the change originally made in commit
      b0118402 (Use absolute path to FindPackageHandleStandardArgs.cmake
      everywhere, 2010-09-28).  This also avoids policy CMP0017 warnings for
      this particular instance of the problem the policy addresses.
      c4275592
    • Kitware Robot's avatar
      KWSys Nightly Date Stamp · 1c8787f3
      Kitware Robot authored
      1c8787f3
  2. 19 Jan, 2011 26 commits
  3. 18 Jan, 2011 1 commit
  4. 17 Jan, 2011 11 commits