使用rust-cpython开发Android库，交叉编译后遇PyModule_Type等符号缺失错误

问题描述 #

我正在开发一款Android应用，基于Python的Kivy框架开发并使用Buildozer构建，同时开发了基于Rust的扩展库，通过cpython crate实现。从Linux x86_64平台交叉编译到aarch64-linux-android目标时，执行cargo build --target aarch64-linux-android可完成编译，但在手机上运行应用时出现以下错误：

• 未添加--release标签编译时：

Traceback (most recent call last):
File "/home/feluk6174/python/lib_test/.buildozer/android/app/main.py", line 26, in <module>
ImportError: dlopen failed: cannot locate symbol "PyModule_Type" referenced by "/data/data/org.test.doxa_test/files/app/doxa_api.so"

• 添加--release标签编译时：

Traceback (most recent call last):
File "/home/feluk6174/python/lib_test/.buildozer/android/app/main.py", line 26, in <module>
ImportError: dlopen failed: cannot locate symbol "PyExc_OverflowError" referenced by "/data/data/org.test.doxa_test/files/app/doxa_api.so"

环境说明 #

参考Mozilla的Rust on Android教程配置了Rust和NDK，之前曾遇到ld: error: unable to find library -lgcc错误，采用GitHub上的修复方案解决后可完成编译，但出现上述符号缺失问题。

相关代码 #

Rust库代码（lib.rs） #

#[macro_use]
extern crate cpython;

use cpython::{Python, PyResult};


py_module_initializer!(doxa_api, doxa_api, PyInit_doxa_api, |py, m | {
    m.add(py, "__doc__", "This module is implemented in Rust")?;
    m.add(py, "test", py_fn!(py, 
        test(a: u8, b:u8) -> PyResult<u8>{
            Ok(a as u8+b as u8)

        }
    ))?;
    Ok(())
});

Cargo.toml配置 #

[package]
name = "doxa_api"
version = "0.1.0"
edition = "2021"


[lib]
name = "doxa_api"
crate-type = ["cdylib"]

[dependencies]
cpython = {version = "*",  features = ["extension-module"]}

.cargo/config.toml配置 #

[target.aarch64-linux-android]
ar = "/home/feluk6174/rust/doxa_api/NDK/arm64/bin/aarch64-linux-android-ar"
linker = "/home/feluk6174/rust/doxa_api/NDK/arm64/bin/aarch64-linux-android-clang"

[target.armv7-linux-androideabi]
ar = "/home/feluk6174/rust/doxa_api/NDK/arm/bin/arm-linux-androideabi-ar"
linker = "/home/feluk6174/rust/doxa_api/NDK/arm/bin/arm-linux-androideabi-clang"

[target.i686-linux-android]
ar = "/home/feluk6174/rust/doxa_api/NDK/x86/bin/i686-linux-android-ar"
linker = "/home/feluk6174/rust/doxa_api/NDK/x86/bin/i686-linux-android-clang"

Python应用代码（main.py） #

from kivy.app import App
from kivy.uix.screenmanager import ScreenManager
import kivy.uix.screenmanager
from kivy.uix.button import Button
from kivy.uix.boxlayout import BoxLayout

import random

import doxa_api

class TestApp(App):

    def build(self):
        sm = ScreenManager()

        sm.add_widget(Screen(name = "screen"))
        
        return sm

class Screen(kivy.uix.screenmanager.Screen):
    def __init__(self, **kwargs):
        super(Screen, self).__init__(**kwargs)
        self.main_box = BoxLayout(orientation = "vertical")
        self.add_widget(self.main_box)

        self.button = Button(text = "try", on_release = self.test)
        self.main_box.add_widget(self.button)


    def test(self, t):
        print("a")
        
        self.button.text = str(doxa_api.test(1, random.randint(0,254)))
        
        

if __name__ == '__main__':
    TestApp().run()

版本信息 #

Python 3.10.9、Kivy 2.1.0、Buildozer 1.5.0、Rust 1.67.0

解决方案 #

核心原因 #

Rust扩展库编译时未链接到Buildozer打包的Android Python运行时对应的Python库，导致运行时无法找到Python内部符号。

具体修复步骤 #

1. 定位Buildozer的Android Python库路径
   Buildozer构建时会下载对应架构的Python库，路径通常为：.buildozer/android/platform/python-for-android/build/other_builds/python3/<arch>/android_<arch>/usr/lib/，例如aarch64架构的路径是.buildozer/android/platform/python-for-android/build/other_builds/python3/arm64-v8a/android_arm64_v8a/usr/lib/，找到对应版本的libpython3.10.so文件。

2. 修改Rust交叉编译的链接参数
   在.cargo/config.toml中为每个Android目标添加rustflags，指定链接到Python库：

   [target.aarch64-linux-android]
   ar = "/home/feluk6174/rust/doxa_api/NDK/arm64/bin/aarch64-linux-android-ar"
   linker = "/home/feluk6174/rust/doxa_api/NDK/arm64/bin/aarch64-linux-android-clang"
   rustflags = [
       "-C", "link-arg=-L/实际路径/buildozer/python/lib",
       "-C", "link-arg=-lpython3.10",
       "-C", "link-arg=-Wl,-rpath=$ORIGIN"
   ]
   
   [target.armv7-linux-androideabi]
   ar = "/home/feluk6174/rust/doxa_api/NDK/arm/bin/arm-linux-androideabi-ar"
   linker = "/home/feluk6174/rust/doxa_api/NDK/arm/bin/arm-linux-androideabi-clang"
   rustflags = [
       "-C", "link-arg=-L/实际路径/buildozer/python/lib/armeabi-v7a",
       "-C", "link-arg=-lpython3.10",
       "-C", "link-arg=-Wl,-rpath=$ORIGIN"
   ]
   
   [target.i686-linux-android]
   ar = "/home/feluk6174/rust/doxa_api/NDK/x86/bin/i686-linux-android-ar"
   linker = "/home/feluk6174/rust/doxa_api/NDK/x86/bin/i686-linux-android-clang"
   rustflags = [
       "-C", "link-arg=-L/实际路径/buildozer/python/lib/x86",
       "-C", "link-arg=-lpython3.10",
       "-C", "link-arg=-Wl,-rpath=$ORIGIN"
   ]
   

   替换/实际路径为你本地的Buildozer工作目录路径。

3. 对齐cpython crate与Python版本
   在Cargo.toml中明确指定cpython版本和对应Python特性，避免版本不兼容：

   [dependencies]
   cpython = {version = "0.18", features = ["extension-module", "python310"]}
   

4. 重新编译打包
   执行cargo build --target aarch64-linux-android --release重新编译Rust库，将生成的doxa_api.so复制到Kivy应用目录，再用Buildozer重新打包应用。

额外注意事项 #

• 若链接时提示找不到Python库，检查库文件名是否为libpython3.so，调整-l参数对应的库名。
• 确保Rust交叉编译使用的NDK版本与Buildozer使用的NDK版本一致，避免链接兼容性问题。

内容的提问来源于stack exchange，提问作者Feluk6174