Android NDK linking

Question

I am trying to build an android application that calls into a C++ backend. This backend uses ZeroMQ for messaging. Per the android build page on the ZeroMQ guide, I have built a native toolchain of ndk version 6 and used that to (successfully) build ZeroMQ. However, when I build my own .so with the JNI implementations, I can't seem to make everything load properly. Specifically, if I call System.LoadLibrary("zmq"), this completes successfully, but if I then call *System.LoadLibrary("my_lib")* I always get an UnsatisfiedLinkError complaining that: ``` Cannot load library reloc_library[1244]: 29 cannot locate zmq_msg_init'... ``` The libmy_lib.so has been generated several different ways, each with no success. After generating it, I always copies libmy_lib.so (as well as libzmq.so) to my android project's folder: libs/armeabi/. ``` # Compile all object files - this part was done for all options /opt/android-toolchain/bin/arm-linux-androideabi-g++ -fpic -c Client_Events.cpp \ Client Wrap…

Accepted Answer

I just learnt how to compile a 2nd library and link it to my main library in android ndk. Let me see if I am of any use to you.

The following is how I create my 2nd library (In my case, I build bullet physics library and the irrlicht rendering engine as 2 separate libraries for my game).

```
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)

LOCAL_C_INCLUDES := HEADER FILES 
LOCAL_MODULE := bullet
LOCAL_SRC_FILES := SRC FILES

LOCAL_ARM_MODE := arm
LOCAL_CFLAGS := $(LOCAL_C_INCLUDES:%=-I%) -O3 -DANDROID_NDK -DDISABLE_IMPORTGL
LOCAL_LDLIBS := -ldl -llog

include $(BUILD_SHARED_LIBRARY)
```

Then copy your libxxxx.so (In my case, libbullet.so and libirrlicht.so) to your jni folder. And in your main library .mk file add the following.

```
LOCAL_PATH := $(call my-dir)

include $(CLEAR_VARS)
LOCAL_C_INCLUDES := (includes for bullet)
LOCAL_MODULE := bullet
LOCAL_SRC_FILES := libbullet.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)
LOCAL_C_INCLUDES := (includes for irrlicht)
LOCAL_MODULE := irrlicht
LOCAL_SRC_FILES := libirrlicht.so
include $(PREBUILT_SHARED_LIBRARY)

include $(CLEAR_VARS)

LOCAL_C_INCLUDES := (includes for bullet + includes for irrlicht + includes for main code)
LOCAL_SRC_FILES := main code src files

LOCAL_MODULE := gamescript

LOCAL_ARM_MODE   := arm
LOCAL_CFLAGS := $(LOCAL_C_INCLUDES:%=-I%) -O3 -DANDROID_NDK -DDISABLE_IMPORTGL
LOCAL_LDLIBS := -lOpenSLES -landroid -ldl -llog

LOCAL_SHARED_LIBRARIES := bullet irrlicht

include $(BUILD_SHARED_LIBRARY)
```

And now, add all the libraries to your java code in right order.

```
System.loadLibrary("bullet");
System.loadLibrary("irrlicht");
System.loadLibrary("gamescript");
```

Android NDK linking

Solution

Problem