如何在 windows/visual studio 上使用 waf 构建 python 扩展模块？

Question

我正在尝试弄清楚如何使用 waf 构建 python 扩展模块，但我被卡住了。考虑一个简单的树，例如：

foo.h

#pragma once

class Foo {
public:
  Foo();
  const int &a() const;
  int &a();

private:
  int m_a;
};

inline const int &Foo::a() const { return m_a; }

inline int &Foo::a() { return m_a; }

foo.cpp

#include "foo.h"

Foo::Foo() : m_a(0) {}

foo.i

%module foo

%{
#include "foo.h"
%}

%include "foo.h"

main.cpp

#include <iostream>

#include "foo.h"

using namespace std;
int main() {
  Foo foo;
  cout << foo.a() << endl;
  foo.a() = 10;
  cout << foo.a() << endl;
}

main.py

import sys
sys.path.append('build')

from foo import Foo

foo = Foo()
print foo.a
foo.a = 1
print foo.a

wscript

import subprocess
from pathlib import Path


def configure(conf):
    conf.env.MSVC_VERSIONS = ["msvc 15.0"]
    conf.env.MSVC_TARGETS = ["x86"]
    conf.load("msvc python swig")
    conf.check_python_version((3, 6, 8))

    # This method is not working properly on windows/virtualenv
    # conf.check_python_headers()

    # Maybe something like this could help?
    # from distutils import sysconfig
    # print(sysconfig.get_python_inc())

    conf.check_swig_version()


def build(bld):
    bld.program(source=["main.cpp", "foo.cpp"], cxxflags=["/EHsc"], target="test")

    bld.shlib(
        features="cxx",
        source="foo.cpp",
        target="foo",
        includes=".",
        export_includes=".",
        name="FOO",
    )

    # bld.program(
    #     source = 'main.cpp',
    #     target = 'main',
    #     use = ['FOO'],
    #     rpath = ['$ORIGIN'],
    # )

    # bld(
    #     features = 'cxx cxxshlib pyext',
    #     source = 'foo.i',
    #     target = '_foo',
    #     swig_flags = '-c++ -python -Wall',
    #     includes = '.',
    #     use  = 'FOO',
    #     rpath = ['$ORIGIN', ],
    #  )


def run(bld):
    root_path = Path(bld.path.abspath())
    subprocess.run(str(root_path / "build/test.exe"))

我在这里已经面临的第一个问题是当我waf distclean configure build时，我会得到这个错误：

(py382_64) D:\swigtest>waf distclean configure build
'distclean' finished successfully (0.006s)
Setting top to                           : D:\swigtest
Setting out to                           : D:\swigtest\build
Checking for program 'CL'                : C:\Program Files (x86)\Microsoft Visual Studio19\Community\VC\Tools\MSVC.26.28801\bin\HostX86\x86\CL.exe
Checking for program 'CL'                : C:\Program Files (x86)\Microsoft Visual Studio19\Community\VC\Tools\MSVC.26.28801\bin\HostX86\x86\CL.exe
Checking for program 'LINK'              : C:\Program Files (x86)\Microsoft Visual Studio19\Community\VC\Tools\MSVC.26.28801\bin\HostX86\x86\LINK.exe
Checking for program 'LIB'               : C:\Program Files (x86)\Microsoft Visual Studio19\Community\VC\Tools\MSVC.26.28801\bin\HostX86\x86\LIB.exe
Checking for program 'MT'                : C:\Program Files (x86)\Windows Kits\bin.0.18362.0\x86\MT.exe
Checking for program 'RC'                : C:\Program Files (x86)\Windows Kits\bin.0.18362.0\x86\RC.exe
Checking for program 'python'            : d:\virtual_envs\py368_32\scripts\python.exe
Checking for program 'swig'              : D:\software\swig\swig.exe
Checking for python version >= 3.6.8     : 3.6.8
Checking for swig version                : 4.0.0
'configure' finished successfully (1.538s)
Waf: Entering directory `D:\swigtest\build'
[1/5] Compiling foo.cpp
[2/5] Compiling main.cpp
[3/5] Compiling foo.cpp
foo.cpp

foo.cpp

[4/5] Linking build\foo.dll
main.cpp

[5/5] Linking build\test.exe
Waf: Leaving directory `D:\swigtest\build'
Build failed
-> missing file: 'D:\swigtest\build\foo.lib'

问题：我该如何解决这个小问题？无论如何，我的主要问题是在 windows 上使用 swig 和 waf 生成 python 扩展模块的正确方法是什么？

Answer 1

您可以通过将库类型从共享 (shlib) 更改为静态 (stlib) 来修复当前构建，即

def build(bld):
    bld.program(source=["main.cpp", "foo.cpp"], cxxflags=["/EHsc"], target="test")

    bld.stlib(
        features="cxx",
        source="foo.cpp",
        target="foo",
        includes=".",
        export_includes=".",
        name="FOO",
    )

要构建 python 扩展模块，您可以使用：

def build(bld):
    bld.program(source=["main.cpp", "foo.cpp"], cxxflags=["/EHsc"], target="test")

    bld.stlib(
        features="cxx",
        source="foo.cpp",
        target="foo",
        includes=".",
        export_includes=".",
        name="FOO",
    )

    bld(
        features = 'cxx cxxshlib pyext',
        source = 'foo.i',
        target = '_foo.pyd',
        swig_flags = '-c++ -python -Wall',
        includes = '.',
        use = 'FOO',
    )

这会将一个 dll 库输出到一个名为 _foo.pyd 的文件和一个 python 脚本 foo.py.
我并不是说这是正确的方法，但它对我有用。

此外，在使用扩展名（例如 from foo import Foo）时，请确保这些文件位于 python 的搜索路径中（使用 PYTHONPATH 或 sys.path.append），否则你可能会得到如下错误：

ModuleNotFoundError: 没有名为“_foo”的模块
ImportError：导入 _foo 时 DLL 加载失败：参数不正确。

当我直接从主目录尝试运行你的 main.py 并通过在 [=20= 中使用绝对（而不是相对）路径解决它时，我遇到了第二个错误] 调用 main.py.

编辑
我使用的是 python 3.8.5 和 Visual Studio 2017
以下是完整的 wscript。
您需要将路径更改为 Python headers 和 CXXFLAGS、LDFLAGS 中引用的库（尽管我想有更好的配置方法）

import subprocess
from pathlib import Path

def configure(conf):
    conf.env.MSVC_VERSIONS = ["msvc 15.9"]
    conf.env.MSVC_TARGETS = ["x64"]
    conf.env.append_value('CXXFLAGS', ["/Id:\tools\Python38\include"])
    conf.env.append_value('LDFLAGS', ["/LIBPATH:d:\tools\Python38\libs"])
    conf.load("msvc python swig")
    conf.check_python_version((3, 6, 8))

    # This method is not working properly on windows/virtualenv
    #conf.check_python_headers()

    # Maybe something like this could help?
    # from distutils import sysconfig
    # print(sysconfig.get_python_inc())

    conf.check_swig_version()


def build(bld):
    bld.program(source=["main.cpp", "foo.cpp"], cxxflags=["/EHsc"], target="test")

    bld.stlib(
        features="cxx",
        source="foo.cpp",
        target="foo",
        includes=".",
        export_includes=".",
        name="FOO",
    )

    bld(
        features = 'cxx cxxshlib pyext',
        source = 'foo.i',
        target = '_foo.pyd',
        swig_flags = '-c++ -python -Wall',
        includes = '.',
        use = 'FOO',
    )



def run(bld):
    root_path = Path(bld.path.abspath())
    subprocess.run(str(root_path / "build/test.exe"))

编辑 2 最初我收到评论中提到的错误，但现在我发现我通过将 foo.i 中的模块声明从文件顶部移动到文件底部而无意中解决了 bug that you've reported。

%{
#include "foo.h"
%}

%include "foo.h"

%module foo

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