在 Windows 上使用 cmake 构建 x86（32 位）项目时使用 64 位 python3 解释器

Question

Background

I have mutiplatform C++ project. Python is used only to download some dependencies from strange places and generate some C++ code. Python is NOT linked to any target, so I do not care what kind of platform it uses.

Problem

When configuring project for Windows 64 bit platform, python is found( find_package ) without any problems. On my machine only Python 3.10.0 for Win64 is installed.

Now when I'm trying build same project for x86 (win32) it fails to configure since can't find 32 bit python.

Here is MCVE:

CMakeLists.txt

cmake_minimum_required(VERSION 3.16)

project(findPythonToGenerate CXX)
find_package(Python3 REQUIRED)

configure_file(test.h.in test.h)

add_executable(foo main.cpp ${CMAKE_CURRENT_BINARY_DIR}/test.h)
target_include_directories(foo PRIVATE ${CMAKE_CURRENT_BINARY_DIR})

main.cpp

#include <iostream>
#include "test.h"

int main()
{
    std::cout << PYTHON_EXE << '\n';
    return 0;
}

test.h.in

#pragma once

#define PYTHON_EXE "@Python3_EXECUTABLE@"

Now when building this for Windows 64 is just fine:

f:\mcve>cmake --version
cmake version 3.20.21032501-MSVC_2

CMake suite maintained and supported by Kitware (kitware.com/cmake).

f:\mcve>rmdir /Q /S build32 build64
The system cannot find the file specified.

f:\mcve>cmake -S . -B build64 -A x64 -Thost=x64 -G "Visual Studio 16 2019"
-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.19044.
-- The CXX compiler identification is MSVC 19.29.30145.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.29.30133/bin/Hostx64/x64/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found Python3: C:/Python310/python.exe (found version "3.10.0") found components: Interpreter
-- Configuring done
-- Generating done
-- Build files have been written to: F:/mcve/build64

f:\mcve>cmake -S . -B build32 -A Win32 -Thost=x86 -G "Visual Studio 16 2019"
-- Selecting Windows SDK version 10.0.18362.0 to target Windows 10.0.19044.
-- The CXX compiler identification is MSVC 19.29.30145.0
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/VC/Tools/MSVC/14.29.30133/bin/Hostx86/x86/cl.exe - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
CMake Error at C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.20/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find Python3 (missing: Python3_EXECUTABLE Interpreter)
Call Stack (most recent call first):
  C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.20/Modules/FindPackageHandleStandardArgs.cmake:594 (_FPHSA_FAILURE_MESSAGE)
  C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.20/Modules/FindPython/Support.cmake:3165 (find_package_handle_standard_args)
  C:/Program Files (x86)/Microsoft Visual Studio/2019/Professional/Common7/IDE/CommonExtensions/Microsoft/CMake/CMake/share/cmake-3.20/Modules/FindPython3.cmake:485 (include)
  CMakeLists.txt:4 (find_package)


-- Configuring incomplete, errors occurred!
See also "F:/mcve/build32/CMakeFiles/CMakeOutput.log".

Question

Can I configure cmake in some way that it give me access to python interpreter ignoring what is the current platform I'm building for? I do not want to install extra python - I do not need it.

I'm building 32 bit platform only to resolve build issues specific for that platform.

Here is similar question , but it is a different flavor, since I do not link anything with python.

Side Note

I think it was OK with older version of cmake . Recently I've updated my Visual Studio 2019 and as a result cmake too. Sadly I can't tell it for sure.

I just checked logs on build machine (which builds all platforms everyday) and on both platforms cmake 3.19 is used and same version of python and I'm sure it is 64 bit version. So looks like regression in cmake 3.20 , so I raised issue .

Answer 1

Ok turns out that problem was type of python installation.

Some time ago I installed python 3.10 for "current user" instead for "local machine". Apparently i didn't had to build for Win32 since that time and when I had to it happen just after MSVC upgrade.

So make sure you install python for "LOCAL MACHINE".