[CMake] cmake 3.12 - python libs / 32 / 64 bits

[Marc CHEVRIER]

FYI, I just deliver a MR (
https://gitlab.kitware.com/cmake/cmake/merge_requests/2624) which fix the
problem of the selection of the library with the wrong architecture.


Le jeu. 15 nov. 2018 à 10:00, Eric Noulard <eric.noulard at gmail.com> a
écrit :

> Le jeu. 15 nov. 2018 à 09:47, Stéphane Ancelot <sancelot at numalliance.com>
> a écrit :
>
>> I agree. That was a debug snippet...but is wrong ... I setted up again
>> the toolchain, but does not help.
>>
>
> If you are using a proper toolchain for 32bit compilation.
> It looks like a bug in the find_package for Python in the cross-compiling
> case.
> Do you have a stripped down example which exhibit the issue?
> Which version of CMake are you using?
>
>
>>  So, I know where are include_dirs and libs  for 32 bits cross compiling,
>> I have to hardcode it like this ?
>>
>>  add_library(python SHARED IMPORTED)
>>  set_target_properties( python PROPERTIES IMPORTED_LOCATION /usr/lib32/
>> libpython2.6.so )
>>  target_include_directories(python SYSTEM ...
>>
>
> I think you can do that but it replaces the use of find_package(Python2
> COMPONENTS Development)
> may be fixing this would be a better long-term solution ?
>
>
>
>>
>>
>> Le 14/11/2018 à 17:53, Marc CHEVRIER a écrit :
>>
>> The way you proceed is wrong.
>> The system configuration is determined during the 'project' function
>> call. Setting information after this call is useless. So, in your example,
>> on a 64bit system, the compilation configuration will be 64bit (variable
>> CMAKE_SIZEOF_VOID_P has value 8).
>> This explain why 'FIND_LIBRARY_USE_LIB32_PATHS' has no effect. This
>> property is taken in consideration only on 32bit systems.
>>
>> Moreover, I am not sure that modifying variable 'CMAKE_SYSTEM_PROCESSOR'
>> is a valid action.
>>
>> To configure a 32bit compilation environment, two possibilities:
>> * using environment variables: env CFLAGS=-m32 CXXFLAGS=-m32 cmake ...
>> * using a toolchain file: see
>> https://cmake.org/cmake/help/v3.13/manual/cmake-toolchains.7.html
>>
>>
>> Le mer. 14 nov. 2018 à 14:06, Stéphane Ancelot <sancelot at numalliance.com>
>> a écrit :
>>
>>> Hi,
>>>
>>> My system is 64 bits but I can cross compile python c modules for 32
>>> bits .
>>>
>>> Unfortunately I don't manage to retrieve python 32 libs , always the 64
>>> bits version is found.
>>>
>>>
>>> here is what I tried :
>>>
>>> cmake_minimum_required(VERSION 3.10)
>>> project(py_autom)
>>>
>>>
>>> set(CMAKE_SYSTEM_PROCESSOR "i686")
>>>
>>> set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -m32" CACHE STRING "c++ flags")
>>> set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS} -m32" CACHE STRING "c flags")
>>>
>>> set_property(GLOBAL PROPERTY FIND_LIBRARY_USE_LIB32_PATHS TRUE)
>>> set_property(GLOBAL PROPERTY FIND_LIBRARY_USE_LIB64_PATHS FALSE)
>>>
>>> include_directories(python2.6)
>>> find_package(Python2 COMPONENTS Development)
>>>
>>>
>>>
>>> message(STATUS "python ${PYTHON_INCLUDE_DIRS} ${Python2_LIBRARIES_DIR}
>>> ${Python2_FOUND}")
>>>
>>> Regards
>>>
>>> Steph
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>> Powered by www.kitware.com
>>
>> Please keep messages on-topic and check the CMake FAQ at:
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>>
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>> information on each offering, please visit:
>>
>> CMake Support: http://cmake.org/cmake/help/support.html
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>>
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>
>
> --
> Eric
>
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