[英]Android ndk-build linker fails to find prebuilt library function
我正在尝试修改本教程,以在我的Android Studio项目中包含一个预建的C库(即,不使用实验性Gradle插件) http://kvurd.com/blog/compiling-a-cpp-library-for-android -with-android-studio /
该库本身来自不会透露源代码的客户端,因此我无法控制构建过程的那部分,但是它们已经遵循了同一教程。
项目构建,加载库工作以及NDK链接(/jni/my-wrapper.c)都可以正常工作,直到我尝试调用在prebuild标头中定义的实际库函数为止。 我收到的错误是:
$ ndk-build
[arm64-v8a] Compile : my-wrapper <= my-wrapper.c
[arm64-v8a] SharedLibrary : libmy-wrapper.so
/Users/me/AndroidStudioProjects/MyProject/app/obj/local/arm64-v8a/objs/my-wrapper/my-wrapper.o: In function `Java_com_my_project_SignInActivity_CallFunction':
/Users/me/AndroidStudioProjects/MyProject/app/jni/my-wrapper.c:44: undefined reference to `MyFunction'
collect2: error: ld returned 1 exit status
make: *** [/Users/me/AndroidStudioProjects/MyProject/app/obj/local/arm64-v8a/libmy-wrapper.so] Error 1
这是我的Android.mk:
LOCAL_PATH := $(call my-dir)
# static library info
include $(CLEAR_VARS)
LOCAL_MODULE := libMyLib
LOCAL_MODULE_FILENAME := libMyLib
LOCAL_SRC_FILES := ../prebuild/libMyLib.a
LOCAL_EXPORT_C_INCLUDES := ../prebuild/include
include $(PREBUILT_STATIC_LIBRARY)
# wrapper info
include $(CLEAR_VARS)
LOCAL_C_INCLUDES += ../prebuild/include
LOCAL_MODULE := my-wrapper
LOCAL_SRC_FILES := my-wrapper.c
LOCAL_STATIC_LIBRARIES := libMyLib
include $(BUILD_SHARED_LIBRARY)
和MyLib.h(注意foobar()可以在标头中正常工作,但是只要我从my-wrapper.c内部调用MyFunction,ndk生成就会失败):
#include <math.h>
#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int MyFunction(some stuff);
int foobar(){return 1;};
最后,my-wrapper.c:
#include <MyLib.h>
jbyte Java_com_my_project_SignInActivity_MyFunction(JNIEnv *env, jobject thiz, some other stuff){
// return MyFunction(some other stuff which I cast to C types); //linker fails if uncommented
return foobar(); //works fine
}
那是C ++杂乱的名字。 您只能从C ++使用它,而不能从C使用它。
如果确实需要从C调用它,则可以这样进行:
extern int _Z12MyFunctionP9my_structPhS1_S1_(/* whatever the function args are */);
jbyte Java_com_my_project_SignInActivity_MyFunction(
JNIEnv *env, jobject thiz, some other stuff) {
return _Z12MyFunctionP9my_structPhS1_S1_(args);
}
这取决于您要调用的代码本身是否兼容(如果是这种情况,则应要求客户端将其API构建为extern "C"
)。
我真的建议您不过将代码移至C ++。
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