Develop Reference

C++ Firebase linking error in android project

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.

Android: How to use an existing C++ static library from your JNI code?

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.

Link shared library under Android NDK

I with success compile library LibXtract to shared object libxtract.so and want to use is in second project.
In mention project I try to compile it on simple function:
#include <com_androidnative1_NativeClass.h>
#include <android/log.h>
#include "libxtract.h"
JNIEXPORT void JNICALL Java_com_androidnative1_NativeClass_showText
(JNIEnv *env, jclass clazz)
{
float mean = 0, vector[] = {.1, .2, .3, .4, -.5, -.4, -.3, -.2, -.1}, spectrum[10];
int n, N = 9;
float argf[4];
argf[0] = 8000.f;
argf[1] = XTRACT_MAGNITUDE_SPECTRUM;
argf[2] = 0.f;
argf[3] = 0.f;
xtract[XTRACT_MEAN]((void *)&vector, N, 0, (void *)&mean);
__android_log_print(ANDROID_LOG_DEBUG, "LIbXtract", "Button pushe2");
}
I have flat structure:
jni/com_androidnative1_NativeClass.c
jni/com_androidnative1_NativeClass.hjni/libxtract.h
jni/other *.h files from libxtract interface
jni/Android.mk
jni/Applicatoin.mk
library libxtract.so I put in mainproject/lib folder
my Android.mk file looks like:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := com_androidnative1_NativeClass.c
LOCAL_MODULE := com_androidnative1_NativeClass
LOCAL_EXPORT_C_INCLUDES := $(LOCAL_PATH)/
LOCAL_LDLIBS += -llog
LOCAL_SHARE_LIBRARIES := libxtract
NDK_MODULE_PATH += $(LOCAL_PATH)/../lib/
include $(BUILD_SHARED_LIBRARY)
and I still got error:
Compile thumb : com_androidnative1_NativeClass <= com_androidnative1_NativeClass.c
SharedLibrary : libcom_androidnative1_NativeClass.so./obj/local/armeabi/objs/com_androidnative1_NativeClass/com_androidnative1_Nativ eClass.o: In function `Java_com_androidnative1_NativeClass_showText':
/home/jack/Projects/AndroidNative1/jni/com_androidnative1_NativeClass.c:20: undefined reference to `xtract'
collect2: ld returned 1 exit status
make: *** [obj/local/armeabi/libcom_androidnative1_NativeClass.so] Error 1
Code came form example of LibXtract and under C++ compile without problems, any ideas?

Your Android make file should be ...
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LIB_PATH := $(LOCAL_PATH)/../lib
LOCAL_SRC_FILES := com_androidnative1_NativeClass.c
LOCAL_MODULE := com_androidnative1_NativeClass
LOCAL_LDLIBS += -llog
LOCAL_LDLIBS += $(LIB_PATH) -lxtract
LOCAL_SHARE_LIBRARIES := libxtract
include $(BUILD_SHARED_LIBRARY)
Try this make file in your second project, and you can successfully build your code without having any error.

In the above answer all is right but exept one.
When we want to link lib we must add -L before LOCAL_LDLIBS dir as below.
LIB_PATH := $(LOCAL_PATH)/../lib
LOCAL_LDLIBS += **-L**$(LIB_PATH) -lxtract
Else it will give error as below
cannot open XXX/../lib: Permission denied

You need to tell Android NDK build scripts about your shared library. Check ${NDK}/doc/PREBUILTS.html for instructions how this can be done. They advise to add Android.mk in the same directory where you have your libXtract.so:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := libXtract
LOCAL_SRC_FILES := libXtract.so
include $(PREBUILT_SHARED_LIBRARY)
Debugging tip: I guess you are using ndk-build to build your "second project". Try running ndk-build with V=99 (try V=99 ndk-build or ndk-build V=99 - my memory failing). This will show you the the exact failing linking command. You should likely have options -lXtract and -L/path/to/libXtract/library. (Sometimes it is convenient to just copy and paste the linking command to run it manually to find the right options for successful linking, before actually fixing the build settings.)
Update: I now see #codetiger's comment seems to point to a same sort of answer (without mentioning the NDK document which is good reading - so I am not deleting this answer).

android external/stlport include in Android.mk build not successfull

I m trying to build an app with android-froyo source in which I am using skia and stl templates,
I have included
MY_INCLUDES=external/zlib external/jpeg external/freetype/include \
frameworks/base/core/jni/android/graphics external/skia/include/core \
external/libpng external/expat/lib <b>external/stlport/stlport</b>
libstlport_cflags := -D_GNU_SOURCE
libstlport_cppflags := -fuse-cxa-atexit
LOCAL_CPPFLAGS := $(libstlport_cppflags)
include $(BUILD_STATIC_LIBRARY)
I get the following error when i try to build the android source with this app, which i kept at packages/apps:
external/stlport/stlport/stl/_new.h:47:50: error: libstdc++/include/new: No such file or directory
Please guide me to rectify this issue.
Thanks
Mohit

As I understand the file which cannot be found by preprocessor is located in bionic folder.
I had the same issue and I solved it by adding the following line:
LOCAL_C_INCLUDES += bionic

I haven't tried this with Android 2.2 but I'm using Android Kitkat (4.4).
To get the stlport library working with our project we included it in our project's Android.mk as so:
include external/stlport/libstlport.mk
This is assuming that on Froyo, there is a libstlport.mk file to include in your build process. In 4.4, there is also a Android.mk file but that builds other code as well and builds stlport as a static library (which is not what we wanted).
You may need to also add the include directory as well, something like: external/stlport/stlport.

cpp
#include <stdio.h>
// The code
// The set of definitions and includes for STLPort
// They used defined() instead of #ifdef.
#define _STLP_HAS_INCLUDE_NEXT 1
#define _STLP_USE_MALLOC 1
#define _STLP_USE_NO_IOSTREAMS 1
#include <stl/config/_android.h>
#include <map>
#include <string>
int main(void)
{
std::string a = "abc";
printf("%s",a.c_str());
return 0;
}
Android.mk
# A simple test for the minimal standard C++ library
#
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_SRC_FILES := test-libstl.cpp
LOCAL_C_INCLUDES += sources/cxx-stl/stlport/stlport
LOCAL_SHARED_LIBRARIES += libstlport
LOCAL_MODULE := test-libstl
include $(BUILD_EXECUTABLE)

android-ndk gnustl_static exe not working

I can't seem to get the following trivial code to compile/link and the problem seems specific to std::wstring and the gnustl_static C++ library. Any help would be appreciated.
main.cpp file:
#include <string>
int main(void)
{
std::wstring wtest(L"Test");
return 0;
}
Application.mk file:
APP_CFLAGS += -fexceptions
APP_STL := gnustl_static
Android.mk file:
LOCAL_PATH := $(call my-dir)
include $(CLEAR_VARS)
LOCAL_MODULE := TestWCharApp
LOCAL_CFLAGS := -D_GLIBCXX_USE_WCHAR_T
LOCAL_SRC_FILES := main.cpp
include $(BUILD_EXECUTABLE)
When attempting to link the above application using gnustl_static I get the following error message:
undefined reference to `std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> >::basic_string(wchar_t const*, std::allocator<wchar_t> const&)'
If I change APP_STL to stlport_static and define _STLP_HAS_WCHAR_T everything seems to compile/link/run fine. I verify it works by uploading the exe to the emulator and running it via the shell.
I'm going to need to use the gnustl implementation for c++ exception support otherwise I'd go with stlport_shared. Any clues as to why the above sample works for stlport_static but not gnustl_static?

It's a problem with the file $NDK/sources/cxx-stl/gnu-libstdc++/Android.mk
Add the following line to that file:
LOCAL_MODULE_FILENAME := libstdc++

What's your target OS? According to this thread, gnustl_static doesn't support wchar_t prior to 2.3.

From the platforms\android-*\arch-arm\usr\include\wchar.h header file:
/* IMPORTANT: Any code that relies on wide character support is essentially
* non-portable and/or broken. the only reason this header exist
* is because I'm really a nice guy. However, I'm not nice enough
* to provide you with a real implementation. instead wchar_t == char
* and all wc functions are stubs to their "normal" equivalent...
*/
Funny though that running the following simple program in an android emulator show that wchar_t is 4 bytes.
#include <stdio.h>
int main(void)
{
printf("Size of wchar is %d\n", sizeof(wchar_t));
return 0;
}
Another thing to consider. The JNI bridge provides two useful ways to marshal string data. GetStringUTFChars (returns const char ) and GetStringChars (returns jchar). How many bytes do you think a jchar is defined as ... 2.

Make sure you run "ndk-build clean" and manually delete your libs/ and obj/
directories.
(Reference)