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The FindPackageHandleStandardArgs module was originally created outside of CMake. It was added for CMake 2.6.0 by commite118a627(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 commitb5f656e0(use the new FIND_PACKAGE_HANDLE_STANDARD_ARGS in some of the FindXXX modules..., 2007-07-18). Then commitd358cf5c(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 commit5f183caa(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 commitb0118402(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 commitdb44848f(Prefer files from CMAKE_ROOT when including from CMAKE_ROOT, 2010-11-17). That change was followed by commitce28737c(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 commita364daf1(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 commitb0118402(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.
54 lines
2.0 KiB
CMake
54 lines
2.0 KiB
CMake
# - Try to find the LibXml2 xml processing library
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# Once done this will define
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#
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# LIBXML2_FOUND - System has LibXml2
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# LIBXML2_INCLUDE_DIR - The LibXml2 include directory
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# LIBXML2_LIBRARIES - The libraries needed to use LibXml2
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# LIBXML2_DEFINITIONS - Compiler switches required for using LibXml2
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# LIBXML2_XMLLINT_EXECUTABLE - The XML checking tool xmllint coming with LibXml2
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#=============================================================================
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# Copyright 2006-2009 Kitware, Inc.
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# Copyright 2006 Alexander Neundorf <neundorf@kde.org>
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#
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# Distributed under the OSI-approved BSD License (the "License");
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# see accompanying file Copyright.txt for details.
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#
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# This software is distributed WITHOUT ANY WARRANTY; without even the
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# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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# See the License for more information.
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#=============================================================================
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# (To distribute this file outside of CMake, substitute the full
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# License text for the above reference.)
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# use pkg-config to get the directories and then use these values
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# in the FIND_PATH() and FIND_LIBRARY() calls
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FIND_PACKAGE(PkgConfig)
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PKG_CHECK_MODULES(PC_LIBXML libxml-2.0 QUIET)
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SET(LIBXML2_DEFINITIONS ${PC_LIBXML_CFLAGS_OTHER})
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FIND_PATH(LIBXML2_INCLUDE_DIR NAMES libxml/xpath.h
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HINTS
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${PC_LIBXML_INCLUDEDIR}
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${PC_LIBXML_INCLUDE_DIRS}
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PATH_SUFFIXES libxml2
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)
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FIND_LIBRARY(LIBXML2_LIBRARIES NAMES xml2 libxml2
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HINTS
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${PC_LIBXML_LIBDIR}
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${PC_LIBXML_LIBRARY_DIRS}
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)
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FIND_PROGRAM(LIBXML2_XMLLINT_EXECUTABLE xmllint)
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# for backwards compat. with KDE 4.0.x:
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SET(XMLLINT_EXECUTABLE "${LIBXML2_XMLLINT_EXECUTABLE}")
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# handle the QUIETLY and REQUIRED arguments and set LIBXML2_FOUND to TRUE if
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# all listed variables are TRUE
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INCLUDE(${CMAKE_CURRENT_LIST_DIR}/FindPackageHandleStandardArgs.cmake)
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FIND_PACKAGE_HANDLE_STANDARD_ARGS(LibXml2 DEFAULT_MSG LIBXML2_LIBRARIES LIBXML2_INCLUDE_DIR)
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MARK_AS_ADVANCED(LIBXML2_INCLUDE_DIR LIBXML2_LIBRARIES LIBXML2_XMLLINT_EXECUTABLE)
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