Android Java Access from JNI

Question

I'm trying to get packageInfo and hence the Signature of the app from Cpp code. Im facing JNI Error and Fatal Signal 6.

My code is:

    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 1");
    jclass android_content_Context =env->GetObjectClass(activity); 
    jmethodID midGetPackageName = env->GetMethodID(android_content_Context, "getPackageName", "()Ljava/lang/String;"); 
    jstring packageName = (jstring)env->CallObjectMethod(activity, midGetPackageName);
    jboolean copy = false;
    const char *nativeString = env->GetStringUTFChars(packageName, &copy);
    __android_log_write(ANDROID_LOG_ERROR, "Tag", nativeString);

    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 2");
    jmethodID midGetPackageManager = env->GetMethodID(android_content_Context, "getPackageManager", "()Landroid/content/pm/PackageManager;"); 
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 3");
    jobject packageManager = env->CallObjectMethod(activity, midGetPackageManager);
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 4");
    jclass android_content_pm_packageManager = env->GetObjectClass(packageManager); 
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 5");
    jmethodID midGetPackageInfo = env->GetMethodID(android_content_pm_packageManager, "getPackageInfo", "(Ljava/lang/String;I)Landroid/content/pm/PackageInfo;");
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 6");
    packageManager = env->CallObjectMethod(activity, midGetPackageManager);
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 6a");   
    jobject packageInfo = env->CallObjectMethod(packageManager, midGetPackageInfo);
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 7");
    jclass android_content_pm_packageInfo = env->GetObjectClass(packageInfo);
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 8");
    jfieldID midSignatureField = env->GetFieldID(android_content_pm_packageInfo, "signatures", "[Landroid/content/pm/Signature");
    __android_log_write(ANDROID_LOG_ERROR, "Tag", "Step 9");

Im getting following error:

05-07 17:01:05.827: E/Tag(2357): Step 1
05-07 17:01:05.827: E/Tag(2357): in.verificationapp
05-07 17:01:05.827: E/Tag(2357): Step 2
05-07 17:01:05.827: E/Tag(2357): Step 3
05-07 17:01:05.827: E/Tag(2357): Step 4
05-07 17:01:05.827: E/Tag(2357): Step 5
05-07 17:01:05.827: E/Tag(2357): Step 6
05-07 17:01:05.827: E/Tag(2357): Step 6a
05-07 17:01:05.827: E/dalvikvm(2357): JNI ERROR (app bug): accessed stale local reference 0x4002d0b1 (index 46124 in a table of size 13)
05-07 17:01:05.827: E/dalvikvm(2357): VM aborting
05-07 17:01:05.827: A/libc(2357): Fatal signal 6 (SIGABRT) at 0x00000935 (code=-6), thread 2357 (ertverification)

Any idea wht is going twong?

I think The Garbage Collector is responsible for this Fatal Error. — Salman Khakwani, May 07 '14 at 12:02

score 0 · Answer 1 · edited May 23 '17 at 12:05

0

You need to rearrange/recreate all your Objects in your code before using them:

Example:

if(__obj_xyz == null)
{
//Re-initialize that variable before (re)using it.
}

Reference Link: JNI ERROR (app bug): accessed stale local reference 0xbc00021 (index 8 in a table of size 8)

I hope this helps.

edited May 23 '17 at 12:05

Community

1
1

answered May 07 '14 at 12:05

Salman Khakwani

6,684
7
33
58

score 0 · Accepted Answer · answered May 09 '14 at 12:33

Figured out the issue.

In line,

    jobject packageInfo = env->CallObjectMethod(packageManager, midGetPackageInfo);

I missed last optional parameter based on the signature

    jobject packageInfo = env->CallObjectMethod(packageManager, midGetPackageInfo, packageName);

Android Java Access from JNI

2 Answers2