I'm trying to modify this tutorial to include a prebuilt C library in my Android Studio project (ie. not using the experimental Gradle plugin) http://kvurd.com/blog/compiling-a-cpp-library-for-android-with-android-studio/
The library itself is coming from a client who won't reveal the source code, therefore I have no control over that part of the build process, however they are already following the same tutorial.
The project builds, load-library works and the NDK link (/jni/my-wrapper.c) works fine, until I try to call the actual library function defined in my prebuild header. The error I'm receiving is:
$ 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
Here's my 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)
And MyLib.h (note that foobar() works fine as it's in the header but as long as I'm calling MyFunction from within my-wrapper.c the ndk-build fails):
#include <math.h>
#include <setjmp.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int MyFunction(some stuff);
int foobar(){return 1;};
Finally, 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
}
That's a C++ mangled name. You can only use it from C++, not from C.
If you really need to call it from C, you might be able to do it like so:
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);
}
That depends on the code you're calling being compatible as such (if that's the case, you should ask the client to build their APIs as extern "C").
I'd really recommend just moving your code to C++ though.
Related
I'm trying to add firebase c++ sdk to my cocos2d-x 3.14 game. So far I've create Android.mk in firebase_cpp_sdk directory:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := firebase-prebuilt
LOCAL_SRC_FILES := libs/android/$(TARGET_ARCH_ABI)/c++/libapp.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
include $(PREBUILT_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE := firebase-analytics
LOCAL_SRC_FILES := libs/android/$(TARGET_ARCH_ABI)/c++/libanalytics.a
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/include
include $(PREBUILT_STATIC_LIBRARY)
Then in my project in Android.mk I've added:
LOCAL_C_INCLUDES += /Users/piotr/Documents/pierdoly/firebase_cpp_sdk/include
LOCAL_STATIC_LIBRARIES += firebase-prebuilt firebase-analytics
$(call import-add-path, /Users/piotr/Documents/pierdoly/firebase_cpp_sdk)
I can sync gradle and build project.
I also can
#include <firebase/app.h>
in AppDelegate.cpp (or h) and it works fine. Even Android studio can see all firebase headers and I can inspect them.
Now, in applicationDidFinishLaunching I've added this:
#if (CC_TARGET_PLATFORM != CC_PLATFORM_ANDROID)
::firebase::App* app = ::firebase::App::Create(::firebase::AppOptions());
#else
::firebase::App* firebaseApp = ::firebase::App::Create(::firebase::AppOptions(), cocos2d::JniHelper::getEnv(), cocos2d::JniHelper::getActivity());
#endif
There's also alternative version via JNICALL from AppActivity.java (to pass correct activity as some say solution above doesn't work):
#if (CC_TARGET_PLATFORM == CC_PLATFORM_ANDROID)
JNIEXPORT void JNICALL Java_org_cocos2dx_cpp_AppActivity_initFirebase(JNIEnv* env, jobject thiz)
{
::firebase::App* app = ::firebase::App::Create(::firebase::AppOptions(), env, thiz);
}
#endif
Yet my problem is: it won't even compile. There's linker error:
Error:(141) undefined reference to 'firebase::App::Create(firebase::AppOptions const&, _JNIEnv*, _jobject*)'
I can clearly "go" into this function in Android Studio and I've rechecked twice parameters I'm giving. They're fine. Yet linker yells at me.
How can I fix linker? What am I missing here?
I had the same problem but found the answer:
It's about the order of the libraries being linked.
You just have to rearrange it like this:
LOCAL_STATIC_LIBRARIES += firebase-analytics firebase-prebuilt
And it should work.
Say thanks to the guys in this github issue
Cocos uses different utils for native libraries build, it can be cmake or ndk util, so check in your frameworks/runtime-src/proj.android/gradle.properties option PROP_BUILD_TYPE and change if it needs from cmake to ndk-build
then look on build.gradle at frameworks/runtime-src/proj.android/app/build.gradle it must use ndk-build correctly.
If you link with c++_shared (LLVM's libc++) and your app uses pthread_create at least once, any calls to sscanf (after pthread_create) will hang in pthread_mutex_lock.
The reason is frivolous use of 'struct FILE' internals in Google's "android_support" auxiliary library. It's likely this structure was changed in Android 5.0 Bionic.
Since NDK r10d eliminates android_support's buggy sscanf implementation (in commit 47e68e84ee043436387a053c1cd47b97cabbb8ca), it is no longer affected. If you must use an older NDK, apply commit 47e68e84ee043436387a053c1cd47b97cabbb8ca to it as an interim fix.
Simple reproduction follows.
Application.mk:
APP_ABI := armeabi
APP_STL := c++_shared
APP_PIE := true
Android.mk:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := test
LOCAL_SRC_FILES := test.cpp
include $(BUILD_EXECUTABLE)
test.cpp:
#include <stdio.h>
#include <pthread.h>
void* threadproc(void *) {
return NULL;
}
int main(int argc, char **argv) {
pthread_t thread;
pthread_create(&thread, NULL, threadproc, NULL); // causes __isthreaded to be set
unsigned int foo;
sscanf("12345", "%u", &foo); // locks up by calling Bionic's flockfile on its own fake FLE
}
I have a android program that has main logic written in NDK. But now I want to evaluate some python codes as part of main logic. So I tried to use this embed python in c http://docs.python.org/2/extending/embedding.html
I created a simple android project, with native.c like this (all I did was just adding python header)
#include <Python.h>
#include <jni.h>
#include <string.h>
#include <android/log.h>
#include <pthread.h>
#define DEBUG_TAG "NDK_AndroidNDK1SampleActivity"
void Java_com_example_com_test_mytest_MainActivity_helloLog(JNIEnv * env, jobject this, jstring logThis)
{
jboolean isCopy;
const char * szLogThis = (*env)->GetStringUTFChars(env, logThis, &isCopy);
__android_log_print(ANDROID_LOG_DEBUG, DEBUG_TAG, "NDK:LC: [%s]", szLogThis);
(*env)->ReleaseStringUTFChars(env, logThis, szLogThis);
}
Here is my Android.mk
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_LDLIBS := -llog `python2.7-config --ldflags`
LOCAL_MODULE := ndk1
LOCAL_SRC_FILES := native.c
LOCAL_CFLAGS := `python2.7-config --cflags`
#LOCAL_SHARED_LIBRARIES := -lpthread
include $(BUILD_SHARED_LIBRARY)
I got following error when compiling (using Mac)
Compile thumb : ndk1 <= native.c
arm-linux-androideabi-gcc: error: i386: No such file or directory
arm-linux-androideabi-gcc: error: x86_64: No such file or directory
arm-linux-androideabi-gcc: error: unrecognized option '-arch'
arm-linux-androideabi-gcc: error: unrecognized option '-arch'
make: *** [obj/local/armeabi/objs/ndk1/native.o] Error 1
Anyone could help please? :D
Python2.7-config was built for a 64 bit i386 system not for Android. It's passing bad arguments to the compiler in the LOCAL_CFLAGS field. Either run one that you built to cross compile on Android or specify the values yourself. Check google for 'Python-For-Android' (Py4A) on how to embed python in an NDK app.
So I'm attempting to use libopus on my native code for an Android application.
My Android.mk file looks like this:
PLATFORM_PREFIX := /opt/android-ext/
LOCAL_PATH := $(PLATFORM_PREFIX)/lib
include $(CLEAR_VARS)
LOCAL_MODULE := libopus
LOCAL_SRC_FILES := libopus.a
include $(PREBUILT_STATIC_LIBRARY)
# I have to redeclare LOCAL_PATH because the library is in /opt/android-ext/
# and my project is somewhere else. Not very elegant.
LOCAL_PATH := /home/sergio/workspace/Project/jni
include $(CLEAR_VARS)
LOCAL_MODULE := opusUtilsNative
LOCAL_SRC_FILES := opusUtilsNative.c
LOCAL_C_INCLUDES += $(PLATFORM_PREFIX)/include
LOCAL_STATIC_LIBRARIES := android_native_app_glue libopus
include $(BUILD_SHARED_LIBRARY)
And my code in opusUtilsNative.c looks like this:
#include "opusUtilsNative.h"
#include <opus/opus.h>
#include <opus/opus_types.h>
JNIEXPORT jbyteArray JNICALL Java_Project_OpusUtils_encode
(JNIEnv * je, jclass jc, jbyteArray data){
int rc;
opus_int16 * testOutBuffer;
unsigned char* opusBuffer;
OpusDecoder *dec;
dec = opus_decoder_create(48000, 2, &rc);
return data;
}
And when I try to build it, it works fine only if I remove the line that uses the "opus_decoder_create" function. Else I will get this:
error: undefined reference to 'opus_decoder_create'
I can see that opus_decoder_create is clearly defined on opus.h, which is clearly being included since if I exclude that line, I'll get an error regarding the opus_int16 and OpusDecoder declarations. How come some definitions are being included and some aren't?
Any help will be greatly appreciated.
This was tricky. After digging around for a bit, I realized I hadn't cross-compiled the opus library correctly, and I didn't have an ARM binary after all.
A good way to verify if your library was cross-compiled correctly:
cd /opt/android-ext/lib #Or wherever the .a file is
ar x libopus.a
file tables_LTP.o #Or any of the .o files generated by ar x
The output should look like this:
tables_LTP.o: ELF 32-bit LSB relocatable, ARM, version 1 (SYSV), not stripped
Otherwise, you might want to double-check your cross-compilation process.
It's error from linker, not from compiler. You forgot to add reference to correspondent libraries to your Android.mk file, do smth like this:
LOCAL_LDLIBS += -lopus
I forgot to integrate one key library
LOCAL_LDLIBS := -lGLESv2
This fixed my problem.
I've seen questions similar to this one, but the scenarios are not exactly the same, nor can I get an answer that works on my problem.
I have the source code for a C++ library. We need to use this library as part of an android application but it also needs to be available for third party to use as a C++ library.
I have a makefile that generates the .a file out of the library's source code, using ndk's compiler. That's the pure C++ part.
On the Java part, I have a simple demo project with a simple activity containing a button. When the button is pressed a call to native code is made.
Everything works fine as long as I don't try to call a function from the library from the JNI function.
Here are the sources for the library:
SimpleMath.h
int Add(int aNumber1, int aNumberB);
SimpleMath.cpp
#include "SimpleMath.h"
int Add(int aNumberA, int aNumberB)
{
return aNumberA + aNumberB;
}
The makefile
APP = simple_app
LIBRARY = simple_library.a
OBJECTS = SimpleMath.o
CFLAGS = -Wall -pedantic
NDK_PATH = /home/jug/perforce/jug_navui_personal_main/Env/Linux/Android/ndk/r7c
CXX = $(NDK_PATH)/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-g++
AR = $(NDK_PATH)/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-ar
SYSTEM_LIBS = -lstdc++ -lm
INCLUDE_PATH += ${NDK_PATH}/platforms/android-9/arch-arm/usr/include
all: $(LIBRARY)
$(LIBRARY):
$(CXX) -c SimpleMath.c
$(AR) rcs simple_library.a SimpleMath.o
clean:
rm *.o *.a
On the java side, these are the files:
hello-jni.c
#include <string.h>
#include <jni.h>
#include "../../../native/simple_library/SimpleMath.h"
jstring Java_com_amstapps_samples_draft08jni_MainActivity_helloJni(JNIEnv* env, jobject obj)
{
// Uncommenting the line below results in undefined-symbol compile error
//int d = Add(1, 2);
return (*env)->NewStringUTF(env, "Hello from JNI!");
}
Android.mk
LOCAL_PATH:= $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := my_simple_library
LOCAL_ARM_MODE := arm
LOCAL_SRC_FILES := ../../../native/simple_library/simple_library.a
include $(PREBUILT_STATIC_LIBRARY)
#include $(BUILD_STATIC_LIBRARY)
include $(CLEAR_VARS)
LOCAL_MODULE_TAGS := eng
LOCAL_ARM_MODE := arm
#LOCAL_PRELINK_MODULE := false
LOCAL_MODULE := hello-jni
LOCAL_SRC_FILES := hello-jni.c
LOCAL_C_INCLUDES := ../../../android/native/simple_library
LOCAL_STATIC_LIBRARIES := my_simple_library
#LOCAL_WHOLE_STATIC_LIBRARIES := my_simple_library
include $(BUILD_SHARED_LIBRARY)
Application.mk
APP_MODULES := my_simple_library hello-jni
As I said, the problem comes when I to actually make use of the functionality in the library from the jni native code in java application.
Now, I'm not longer sure whether my problem is in the static-library's makefile or on the Android.mk. I first thought it must have to do with the generation of the library itself, but at this point, after seeing there are so many options I didn't know about in Android.mk, I have to admit I have no clue.
What else..?
Oh, yes, I also noticed my pure C++ library is using cpp extension whereas the jni code in java project is using c extension. I tried to have the latter using cpp as well, but compiler complains. Could this be part of the problem?
The error code that I get when trying to compile the Android.mk file is "undefined symbol", so, is the list of functions in simple_library.a (there's actually 1 function) not visible to hello-jni.c because of it being C++ and not plain C?
Another thing you might notice is I'm trying to build the static library on its own makefile as opposed to generating it with Android.mk; there's a reason for that, but at this point I would also be happy if I had to have it in generated by Android.mk if that's what it takes.
I don't see any way to add an attachment in here so that to share a zip with the project.
Let me know if there's something I'm missing.. Otherwise the code is in a depot in bitbucket, so I can easily share it with anyone having an account there too.
Thanks for you answers.
You write a lot of correct things, but you're missing just one.
The function's name gets mangled in C++. And in the .so file you do not get "Add" symbol, but something like "Add#8i". To avoid mangling just use the
extern "C" int Add(int x, int y)
declaration in the .cpp file and in the .h.
Usually one also adds the
/// Some .h file
#ifdef __cplusplus
extern "C" {
#endif
/// Your usual C-like declarations go here
#ifdef __cplusplus
} // extern "C"
#endif
And the
extern "C"
for each of the exported functions in the .cpp file.