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

[Marc CHEVRIER]

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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