[CMake] suspicious behaviour of FindPkgConfig
Nizar Khalifa Sallem
nksallem at laas.fr
Fri Jan 7 05:57:13 EST 2011
At Fri, 07 Jan 2011 08:35:22 +0100,
Michael Wild wrote:
>
> 1. Flann uses CMake, so it should install a FlannConfig.cmake (possibly
> in addition to the currently installed flann.pc). This would obsolete
> all issues below.
>
>
> 2. Since Flann only comes with a pkg-config module and there's no
> FindFlann.cmake module in CMake, the OP could either write his own
> (refer to the docs on the find_package command and read the
> ${CMAKE_ROOT}/Modules/readme.txt file).
>
>
> 3. The OP could use the FindPkgConfig.cmake module, but then he should
> do so correctly:
>
> # find FLANN with pkg-config
> find_package(PkgConfig REQUIRED)
> pkg_check_modules(FLANN REQUIRED flann)
>
> # find Doxygen
> find_package(Doxygen)
>
> # later on, when FLANN is needed for compiling
> link_directories(${FLANN_LIBRARY_DIRS})
> include_directories(${FLANN_INCLUDE_DIRS})
> if(FLANN_CFLAGS)
> add_definitions(${FLANN_CFLAGS})
> endif(FLANN_CFLAGS)
>
> # and even later, when FLANN is needed for linking
> target_link_libraries(SomeTarget ${FLANN_LIBRARIES})
>
>
> 4. The OP should note that pkg-config is fundamentally flawed and he
> really should consider item 2 of this list.
>
>
> 5. The code shown by the OP is broken on so many levels, it should be
> purged from the archives of this mailing list. I'm sure some beginner
> will find it with google and then it will start spreading like a virus,
> resulting in gazillions of users flooding this mailing list venting
> their frustration with CMake ;-)
>
> Seriously, though: **NEVER**, **EVER**, define macros/functions with
> names of existing built-in commands (unless you actually know exactly
> what you are doing, that is. The OP clearly didn't). FIND_PACKAGE is a
> _very_ important built-in CMake command and by defining a macro with
> that name, the OP effectively broke CMake for his purposes, which is why
> the find_package(Doxygen) call failed.
>
> For completeness: If you redefine a built-in command with a
> macro/function, the original command is renamed by appending an
> underscore (_) to its name. So find_package_(Doxygen) should work in the
> posted code.
>
>
> I hope this helps a bit
>
>
> Michael
>
> On 01/07/2011 12:27 AM, Ryan Pavlik wrote:
> > FindPkgConfig and find_package are not really related: some scripts for
> > find_package do use pkg-config to help them, but you shouldn't need to check
> > for it yourself.
> >
> > Also, find scripts shouldn't be used with "include".
> >
> > It looks a bit like build system overkill: this should do roughly the same
> > thing, but simpler and more reliably. Though I'm sure you probably have
> > more libraries (otherwise I'm really confused by your use of a foreach
> > loop), something like this is clearer, and at least in my eyes, the tradeoff
> > of small code duplication (which isn't always wrong because some find
> > modules work differently) for the clarity (versus all those nested variable
> > evaluations) is definitely worth it.
> >
> > cmake_minimum_required(VERSION 2.6.4 FATAL_ERROR)
> >
> > project(test CXX C)
> >
> > find_package(flann)
> > if(FLANN_FOUND)
> > set(HAVE_FLANN YES)
> > include_directories(${FLANN_INCLUDE_DIRS})
> > list(APPEND LIBS ${FLANN_LIBRARIES})
> > endif()
> >
> > find_package(Doxygen)
> >
> >
> > On Thu, Jan 6, 2011 at 11:39 AM, Nizar Khalifa Sallem <nksallem at laas.fr>wrote:
> >
> >> Hi all,
> >>
> >> I am getting in trouble with the FindPkgConfig module. Here is a piece
> >> of rather bigger CMakeLists.txt file that doesn't success to find
> >> Doxygen although installed on the machine(ubuntu 10.4, cmake 2.8.3)
> >>
> >>
> >> # $Id$ #
> >> #
> >> ----------------------------------------------------------------------------
> >> # A CMakeLists.txt file to test FindPkgConfig
> >> #
> >> ----------------------------------------------------------------------------
> >>
> >> set(CMAKE_ALLOW_LOOSE_LOOP_CONSTRUCTS true)
> >>
> >> # it MUST go before PROJECT(Jafar) in order to work
> >> if (NOT CMAKE_INSTALL_PREFIX)
> >> set(CMAKE_INSTALL_PREFIX ${CMAKE_BINARY_DIR} CACHE INTERNAL "" FORCE)
> >> endif()
> >>
> >> cmake_minimum_required(VERSION 2.6.4 FATAL_ERROR)
> >>
> >> project(test CXX C)
> >>
> >> include(CheckIncludeFile)
> >>
> >> macro(FIND_PACKAGE package_name)
> >> string(TOUPPER "${package_name}" PACKAGE_NAME)
> >> # string(TOUPPER "${package_name}_FOUND" PACKAGE_NAME_FOUND)
> >> pkg_check_modules(${PACKAGE_NAME} ${package_name})
> >> # message(STATUS "finding ${package_name}
> >> ${${PACKAGE_NAME_FOUND}}")
> >> endmacro(FIND_PACKAGE package_name)
> >>
> >> include(FindPkgConfig)
> >> if(PKG_CONFIG_FOUND)
> >> foreach(package
> >> flann)
> >> string(TOUPPER "${package}" PACKAGE)
> >> string(TOUPPER "HAVE_${package}" HAVE_PACKAGE)
> >> string(TOUPPER "${package}_FOUND" PACKAGE_FOUND)
> >> find_package(${package})
> >> set(${HAVE_PACKAGE} ${${PACKAGE_FOUND}})
> >> if(${PACKAGE_FOUND})
> >> string(TOUPPER "LIBS_MAP_${package}"
> >> LIBS_MAP_PACKAGE)
> >> set(${LIBS_MAP_PACKAGE} "${PACKAGE}")
> >> set(LIBS ${LIBS} ${${PACKAGE}_LIBRARIES})
> >> include_directories(${${PACKAGE}_INCLUDE_DIRS})
> >> endif(${PACKAGE_FOUND})
> >> endforeach(package)
> >> else(PKG_CONFIG_FOUND)
> >> message(ERROR " pkgconfig not found you won't be able to build some
> >> modules")
> >> endif(PKG_CONFIG_FOUND)
> >>
> >> find_package(Doxygen)
> >>
> >> ==================================================================
> >> It says :
> >> Running CMake to regenerate build system...
> >> -- checking for module 'Doxygen'
> >> -- package 'Doxygen' not found
> >>
> >> I get it work by putting find_package(Doxygen) before
> >> include(FindPkgConfig) statement. Can someone explain me this strange
> >> behaviour please ?
> >>
> >> Cheers,
> >> --
> >> Nizar
>
>
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Well,
I am really sorry for the stupid bug but I didn't pay a lot attention
and as suggested named my macro find_package two.
PS: cmae is great :)
Cheers,
--
Nizar
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