Why is passing java long as pointer to struct in c++ library crashing app?

I am trying to hold a reference in a c++ libary through java follwing along the steps outlined in this thread: https://stackoverflow.com/questions/1632367/passing-pointers-between-c-and-java-through-jni

However, when I run the application it instantly crashes. Can someone please take a look and see what I may be doing wrong? Been pulling my hair too long...

EDIT:
Added full code and stack trace at request of super user michael. The code runs fine if the testingHandle bool is set to false. Crashes if it is set to true

Edit 2: And, it was a typo... fixed below

application code:

package com.AndroidCPP;
import android.app.Activity;
import android.widget.TextView;
import android.os.Bundle;
import android.util.Log;
public class AndroidCPP extends Activity
{
//Set Activity tag for logging (adb command: adb logcat *:s AndroidCPP:V)
private static final String TAG = "AndroidCPP";
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
boolean testingHandle = true;
if(testingHandle)
{
DynamicLib newLib = new DynamicLib();
newLib.Init();
newLib.CleanUp();
}	
//pull device info from lib
int libNum = DynamicLib.GetNumber(3);
String ipAddress = DynamicLib.GetLocalIPv4();
String serialNumber = DynamicLib.GetSerialNumber();
//Textview will only work on regular android device, you'll be in the black void if run on a quest
TextView  tv = new TextView(this);
String textViewString = String.format("Here is a number that was the cause of addition in a C++ library : %d \n", libNum);
textViewString += String.format("Here is the IP Adrress Pulled from the DL:  %s", ipAddress);
textViewString += "\n";
textViewString += "Here is the IP Address Pulled from Java Utils: " + Utils.getIPAddress(true);
textViewString += "\n";
textViewString += String.format("Here is the serial Number pulled from DL: %s", serialNumber);
tv.setText(textViewString);
//Logcat Log
Log.v(TAG, "");
Log.v(TAG, "***************");
Log.v(TAG, "JAVA ip: " + Utils.getIPAddress(true));
Log.v(TAG, "C++ ip :" + ipAddress);
Log.v(TAG, "JAVA MAC : " + Utils.getMACAddress("wlan0"));
Log.v(TAG, "Serial Number : " + serialNumber);
setContentView(tv);
}
}

java side:

package com.AndroidCPP;
class DynamicLib
{
static{
System.loadLibrary("DynamicLib");
}
long testHandle = 0;
public void Init()
{
testHandle = CreateMemory();
}
public void CleanUp()
{
FreeMemory(testHandle);
}
public native long CreateMemory();
public native void FreeMemory(long ptr);
public static native int GetNumber(int testParameter);
public static native String GetLocalIPv4();
public static native String GetSerialNumber();
}

CPP side:

#include <jni.h>
#include <android/log.h>
#include "TestClass.h"
#include "IPFetch.h"
#define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, "DynamicLib", __VA_ARGS__))
#define LOGW(...) ((void)__android_log_print(ANDROID_LOG_WARN, "DynamicLib", __VA_ARGS__))
extern "C" {
JNIEXPORT jlong JNICALL Java_com_AndroidCPP_DynamicLib_CreateMemory(JNIEnv* env, jobject obj)
{
DynamicLib::testStruct* newPtr = new DynamicLib::testStruct();
return (jlong)newPtr;
}
JNIEXPORT void JNICALL Java_com_AndroidCPP_DynamicLib_FreeMemory(JNIEnv* env, jobject obj, jlong ptr)
{
DynamicLib::testStruct* tempStructPtr = (DynamicLib::testStruct*)ptr;
delete tempStructPtr;
}
JNIEXPORT int JNICALL Java_com_AndroidCPP_DynamicLib_GetNumber(JNIEnv* env, jobject obj, int testParameter)
{
LOGI("Calling Get Number From Dynamic Lib With Test Parameter %d", testParameter);
DynamicLib::TestClass testClass;
return testClass.AddTwoNumbers(testParameter, 2);
}
JNIEXPORT jstring JNICALL Java_com_AndroidCPP_DynamicLib_GetLocalIPv4(JNIEnv* env, jobject obj)
{
DynamicLib::IPFetch ipFetch;
jstring returnString = env->NewStringUTF(ipFetch.FetchLocalIPv4().c_str());
return returnString;
}
JNIEXPORT jstring JNICALL Java_com_AndroidCPP_DynamicLib_GetSerialNumber(JNIEnv* env, jobject obj)
{
DynamicLib::IPFetch ipFetch;
return env->NewStringUTF(ipFetch.FetchSerialNumber().c_str());
}
}

separate headers/cpp (not part of handle, but functioning like they should

namespace DynamicLib {
struct testStruct {
int x = 10;
int y = 10;
};
class TestClass
{
public:
TestClass() = default;
~TestClass();
int AddTwoNumbers(int a, int b);
};
}
#include <string.h>
#include <iostream>
namespace DynamicLib
{
class IPFetch
{
public:
IPFetch() = default;
~IPFetch();
std::string FetchLocalIPv4();
std::string FetchSerialNumber();
};
}
#include "IPFetch.h"
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <stdio.h>
#include <dlfcn.h>
#include <android/log.h>
#include <string>
#include <sstream>
using namespace DynamicLib;
IPFetch::~IPFetch()
{
}
std::string IPFetch::FetchLocalIPv4()
{
int s;
struct ifreq ifr;
char stringBuffer[16];
const char *ipCast = "%d.%d.%d.%d";
s = socket(AF_INET, SOCK_DGRAM, 0);
strcpy(ifr.ifr_name, "wlan0");
ioctl(s, SIOCGIFADDR, &ifr);
unsigned char *ip = (unsigned char*)(&ifr.ifr_addr.sa_data[2]);
close(s);
snprintf(stringBuffer, sizeof(stringBuffer), ipCast, ip[0], ip[1], ip[2], ip[3]);
return std::string(stringBuffer);
}
std::string IPFetch::FetchSerialNumber()
{
typedef int(*PFN_SYSTEM_PROP_GET)(const char *, char *);
#if (__ANDROID_API__ >= 21)
static PFN_SYSTEM_PROP_GET __real_system_property_get = NULL;
if (!__real_system_property_get) {
// libc.so should already be open, get a handle to it.
void *handle = dlopen("libc.so", RTLD_NOLOAD);
if (!handle) {
__android_log_print(ANDROID_LOG_ERROR, "foobar", "Cannot dlopen libc.so: %s.\n", dlerror());
}
else {
__real_system_property_get = (PFN_SYSTEM_PROP_GET)dlsym(handle, "__system_property_get");
}
if (!__real_system_property_get) {
__android_log_print(ANDROID_LOG_ERROR, "foobar", "Cannot resolve __system_property_get(): %s.\n", dlerror());
}
}
char buff[64];
std::ostringstream stm;
stm << ((*__real_system_property_get)("ro.boot.serialno", buff));
std::string returnVal = stm.str();
return std::string(buff);
#endif // __ANDROID_API__ >= 21
return "-1";
}

Error output/stack trace, you can see it is failing to execute the CreateMemory() function

05-05 00:49:39.831 11430 11430 I chatty  : uid=10297(com.AndroidCPP) identical 2 lines
05-05 00:49:40.031 11430 11430 I System.out: waiting for debugger to settle...
05-05 00:49:40.231 11430 11430 I System.out: debugger has settled (1306)
05-05 00:49:40.244  1503  2852 E InputDispatcher: Window handle Window{b5ce578 u0 Waiting For Debugger: com.AndroidCPP} has no registered input channel
05-05 00:49:40.523 11430 11430 I com.AndroidCPP: The ClassLoaderContext is a special shared library.
05-05 00:49:41.116 11430 11430 E com.AndroidCPP: No implementation found for long com.AndroidCPP.DynamicLib.CreateMemory() (tried Java_com_AndroidCPP_DynamicLib_CreateMemory and Java_com_AndroidCPP_DynamicLib_CreateMemory__)
05-05 00:49:41.117 11430 11430 D AndroidRuntime: Shutting down VM
05-05 00:49:41.141 11430 11430 E AndroidRuntime: FATAL EXCEPTION: main
05-05 00:49:41.141 11430 11430 E AndroidRuntime: Process: com.AndroidCPP, PID: 11430
05-05 00:49:41.141 11430 11430 E AndroidRuntime: java.lang.UnsatisfiedLinkError: No implementation found for long com.AndroidCPP.DynamicLib.CreateMemory() (tried Java_com_AndroidCPP_DynamicLib_CreateMemory and Java_com_AndroidCPP_DynamicLib_CreateMemory__)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at com.AndroidCPP.DynamicLib.CreateMemory(Native Method)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at com.AndroidCPP.DynamicLib.Init(DynamicLib.java:14)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at com.AndroidCPP.AndroidCPP.onCreate(AndroidCPP.java:26)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:7825)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.Activity.performCreate(Activity.java:7814)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1306)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:3245)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:3409)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.servertransaction.LaunchActivityItem.execute(LaunchActivityItem.java:83)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.executeCallbacks(TransactionExecutor.java:135)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.servertransaction.TransactionExecutor.execute(TransactionExecutor.java:95)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.ActivityThread$H.handleMessage(ActivityThread.java:2016)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.os.Handler.dispatchMessage(Handler.java:107)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.os.Looper.loop(Looper.java:214)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at android.app.ActivityThread.main(ActivityThread.java:7356)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at java.lang.reflect.Method.invoke(Native Method)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
05-05 00:49:41.141 11430 11430 E AndroidRuntime: 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:930)
05-05 00:49:41.157  1503 11483 I DropBoxManagerService: add tag=data_app_crash isTagEnabled=true flags=0x2
05-05 00:49:41.157  1503  2991 W ActivityTaskManager:   Force finishing activity com.AndroidCPP/.AndroidCPP
05-05 00:49:41.182 11430 11430 I Process : Sending signal. PID: 11430 SIG: 9
05-05 00:49:41.184  1503  1579 E libprocessgroup: set_timerslack_ns write failed: No such process
05-05 00:49:41.218  1503  3340 I ActivityManager: Process com.AndroidCPP (pid 11430) has died: vis+99 TOP 
05-05 00:49:41.220   937   937 I Zygote  : Process 11430 exited due to signal 9 (Killed)

"No implementation found for long com.AndroidCPP.DynamicLib.CreateMemory"

You've got a typo in your code: Java_com_AndroidCPP_DynamciLib_CreateMemory

That should be: Java_com_AndroidCPP_DynamicLib_CreateMemory

Same thing for FreeMemory.

How long is your C++ long?

The size in C++ is implementation-specific, and the only requirement is that it be at least 32 bits. Some compilers have long and int be 32 bits, with pointers being 64 bits.

Best to use something like uint64_t in the C++ code.

This line is problematic:

return (long)newPtr;

long and jlong are not the same datatype, the latter might be wider. Cast to jlong instead.

return (jlong)newPtr;