关于链接器：使用Android Studio中的NDK将不带标题的共享对象库链接

Linking shared object library without headers with NDK in Android Studio

我有一个为arm-linux-androideabi编译的共享库文件faceblaster-engine.so，放在Android Studio的jniLibs文件夹中。我在jni文件夹中还有一个简单的cpp文件。

我的库是用Rust编写的，所以没有头文件，我想通过cpp文件在其中调用函数，但似乎无法正确链接库。为了测试，我做了一个简单的函数：

锈

1
2
3
4

#[no_mangle]
pub extern fn rust_test() -> c_int {
82 as c_int
}

C ++

1
2
3
4
5
6
7
8
9
10
11
12

extern"C" {

// Test for calling rust function
int rust_test();

jint
Java_com_fureality_faceblaster_MainActivity_testRustLaunch(JNIEnv* env, jobject thiz)
{
return rust_test();
}

} // End extern

Android.mk

1
2
3
4
5
6
7
8
9
10
11
12

LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_MODULE := faceblaster-engine
LOCAL_SRC_FILES := ../jniLibs/$(TARGET_ARCH_ABI)/libfaceblaster-engine.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_MODULE := faceblaster
LOCAL_SRC_FILES := gl-tests.cpp
LOCAL_SHARED_LIBRARIES := faceblaster-engine
include $(BUILD_SHARED_LIBRARY)

错误

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15

/home/nathan/Development/projects/faceblaster-android/app/src/main/jni/gl-tests.cpp

Error:(23) undefined reference to `rust_test'
Error:error: ld returned 1 exit status
make: *** [/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/obj/local/arm64-v8a/libfaceblaster.so] Error 1
Error:Execution failed for task ':app:compileDebugNdk'.
> com.android.ide.common.internal.LoggedErrorException: Failed to run command:
/home/nathan/Development/bin/android-ndk-r10d/ndk-build NDK_PROJECT_PATH=null APP_BUILD_SCRIPT=/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/Android.mk APP_PLATFORM=android-21 NDK_OUT=/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/obj NDK_LIBS_OUT=/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/lib APP_ABI=all
Error Code:
2
Output:
/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/obj/local/arm64-v8a/objs/faceblaster//home/nathan/Development/projects/faceblaster-android/app/src/main/jni/gl-tests.o: In function `Java_com_fureality_faceblaster_MainActivity_testRustLaunch':
/home/nathan/Development/projects/faceblaster-android/app/src/main/jni/gl-tests.cpp:23: undefined reference to `rust_test'
collect2: error: ld returned 1 exit status
make: *** [/home/nathan/Development/projects/faceblaster-android/app/build/intermediates/ndk/debug/obj/local/arm64-v8a/libfaceblaster.so] Error 1

我不知道我的makefile没有被提取还是正确？有人对如何正确链接此.so文件和注册我要使用的功能有想法吗？

在此先感谢您的帮助！

编辑-添加了Java源代码和rust代码编译方法

爪哇

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19

public class MainActivity extends Activity {

// External libraries to load
static {
System.loadLibrary("faceblaster-engine");
System.loadLibrary("faceblaster");
}

// External functions to register
public native int testRustLaunch();

@Override
protected void onCreate(Bundle savedInstanceState) {
// Other stuff omitted for brevity
Log.d(TAG,"Testing call...");
int test = testRustLaunch();
Log.d(TAG,"Received:" + test);
}
}

锈编译

1
2
3
4
5
6
7
8
9
10

cargo build --target=arm-linux-androideabi

# /project/.cargo/config file
[target.arm-linux-androideabi]
linker ="/opt/ndk_standalone/bin/arm-linux-androideabi-gcc"

# Cargo.toml
[lib]
name ="faceblaster-engine"
crate_type = ["dylib"]

编辑2

我已经通过build.gradle脚本进行了编辑，我知道现在正在读取和使用我的Android.mk，但是仍然遇到相同的编译错误:(

编辑3

事实证明，以下两个答案都有助于解决问题。这主要是因为Android Studio的一部分没有提取我的makefile，生锈代码未正确声明为#[no_mangle] pub extern，而我的makefile却全部被劫持了。