使用ProGuard时如何保留从JNI访问的类变量

Question

I've read through the manual -keep options but my JNI code is getting SIGSEGV when it accesses any of my Java class variables.

V/MyClass:native:my_native_method(30592): entered
I/DEBUG   (18752): *** *** *** *** *** *** *** *** *** *** *** *** *** *** *** ***
I/DEBUG   (18752): Build fingerprint: 'samsung/DEVICE/DEVICE:ANDROIDVERSION/XXXXXX/XXXXXX:user/release-keys'
I/DEBUG   (18752): pid: 30592, tid: 30619  >>> com.example <<<
I/DEBUG   (18752): signal 11 (SIGSEGV), code 1 (SEGV_MAPERR), fault addr 0000000c
I/DEBUG   (18752):  r0 413f5890  r1 409b1fc8  r2 00000000  r3 00000001
I/DEBUG   (18752):  r4 1d400256  r5 00000000  r6 5ca8fa80  r7 1d400256
I/DEBUG   (18752):  r8 5ca8fbe8  r9 56c6cea0  10 00000000  fp 5ca8fbfc
I/DEBUG   (18752):  ip 409ad030  sp 5ca8fa10  lr 400c4260  pc 40950524  cpsr 60000030
I/DEBUG   (18752):  d0  0000006442c80000  d1  3ff0000042c80000
I/DEBUG   (18752):  d2  0000000000000000  d3  43ec000043a60000
I/DEBUG   (18752):  d4  0000000000000000  d5  0000000000000000
I/DEBUG   (18752):  d6  00000000c2600000  d7  3f8000003f800000
I/DEBUG   (18752):  d8  43ec000044930000  d9  44084000448d0000
I/DEBUG   (18752):  d10 0000000000000000  d11 0000000000000000
I/DEBUG   (18752):  d12 0000000000000000  d13 0000000000000000
I/DEBUG   (18752):  d14 0000000000000000  d15 0000000000000000
I/DEBUG   (18752):  scr 60000010

By adding some log statements I could see that this happens whenever the native code accesses one of the Java class variables.

At first I tried:

-keep class com.example.MyClass {
    String mystring1;
    static String mystring2;
    byte[] mybytearray1;
    ...
}

I've even tried this in my proguard-project.txt:

-keep class com.example.MyClass {
    *;
}

But still I get SIGSEGV in my JNI library.

I looked in bin/proguard/seeds.txt and the variables ARE in there.

But something goes wrong.

The code runs perfectly until I enable ProGuard.

UPDATE: In researching this I am wondering whether the requirement about Android GC being able to relocate pointers is affecting ProGuard. In my native C code I have this:

JNIEXPORT jint JNICALL  Java_com_example_MyClass_my_1native_1method(
    JNIEnv* env,
    jobject thizz)
{
    jobject thiz = (*env)->NewGlobalRef(env,thizz); // prevent newer GC from relocating pointer

Could this be the source of the problem for ProGuard?

Answer 1

This project involves a main project that incorporates a number of subprojects. It is one of the subproject libraries that calls the native library. I had put the -keep class *; preservation into this subproject's proguard-project.txt. I didn't think it needed to be put into the main project proguard file. But that was the problem. As soon as I duplicated the library subproject's -keep class statement in the main project proguard file then the SIGSEGV disappeared. It would be nice if proguard could make it unnecessary to duplicate entries like this.