2

我正在尝试将有效的 C JNI 绑定转换为 C++，因为我想从一些 Java 代码链接到 C++ 源代码（图像处理算法的开源实现）。我让一切都在 C 中工作，这包括 Java 类、JNI 绑定的 C 版本和构建系统，并且不包括使用 C++ 源代码。

我现在正在尝试将 JNI 绑定转换为 C++，以便将 C++ 源添加到构建系统并从绑定中调用它，但我遇到了一个未定义的符号。

我的 Makefile 非常简单：

GCC = gcc -Wall -g -std=gnu99
CXX = g++ -Wall -g
LIBOBJS = parallelsurf_jni.o

LIB=libparallelsurf.so
DESTLIB=../../lib/$(LIB)

all: $(DESTLIB)


$(DESTLIB): $(LIB)
    cp $(LIB) $(DESTLIB)

libparallelsurf.so: parallelsurf_ParallelSURF.h $(LIBOBJS)
    ld --shared $(LIBOBJS) -o libparallelsurf.so 

parallelsurf_ParallelSURF.h:
    echo "Rebuilding JNI headers. Ensure java file has been recently built."
    javah -classpath ../../parallelsurf.jar -jni parallelsurf.ParallelSURF

clean:
    rm -f $(LIBOBJS) *~ parallelsurf_ParallelSURF.h $(LIB) $(DESTLIB) $(LIBOBJS)

JNI_INCLUDES = -I/usr/lib/jvm/java-6-sun/include/ -I/usr/lib/jvm/java-6-sun/include/linux -I/usr/lib/jvm/java-6-openjdk/include/

%.o: %.cpp
    $(CXX) -shared -O2 -c -fPIC -fno-omit-frame-pointer -fno-stack-protector -D_REENTRANT $< $(JNI_INCLUDES)

My header file is thus automatically generated with javah and I don't appear to have mangled it when copying from .h to .cpp. I do not have extern "C" blocks in the .cpp file, as guided by this post.

I also included a pragma as guided by this post: Undefined Symbol _gxx_personality_v0 on link. The pragma is #pragma GCC java_exceptions

Now, that undefined symbol (gxx_personality) seems to be well referenced/documented on the web. A number of posts point to this comment on C++/Java exception handling, which suggests using that pragma. However, after including that pragma, I get another undefined symbol that is not well covered (I get exactly 1 Google hit): _gcj_personality_v0

Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/chardson/chardson/parallelsurf/lib/libparallelsurf.so: /home/chardson/chardson/parallelsurf/lib/libparallelsurf.so: undefined symbol: __gcj_personality_v0
    at java.lang.ClassLoader$NativeLibrary.load(Native Method)
    at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1750)
    at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1675)
    at java.lang.Runtime.loadLibrary0(Runtime.java:840)
    at java.lang.System.loadLibrary(System.java:1047)
    at parallelsurf.ParallelSURF.<clinit>(ParallelSURF.java:17)
    at testpsurf.<init>(testpsurf.java:11)
    at testpsurf.main(testpsurf.java:23)

I'm not sure what to make of this undefined symbol, and I have no idea where else to turn. Perhaps there's just a mistake in my JNI code that could be fixed to get rid of this problem? My JNI C++ code is included below for completeness.

#include <jni.h>
#include <stdio.h>
#include <assert.h>

#pragma GCC java_exceptions

/*
 * Class:     parallelsurf_ParallelSURF
 * Method:    parallelsurf_get_keypoints
 * Signature: (II[FZ)Ljava/util/ArrayList;
 */
JNIEXPORT jobject JNICALL Java_parallelsurf_ParallelSURF_parallelsurf_1get_1keypoints
  (JNIEnv *jenv, jclass jcls, jint width, jint height, jfloatArray gray, jboolean rotInvariant)
{
    // init arraylist class
    jclass arrayListClass = jenv->FindClass("java/util/ArrayList");
    assert(arrayListClass != NULL);

    jmethodID alInitMethodId = jenv->GetMethodID(arrayListClass, "<init>", "()V");
    assert(alInitMethodId != NULL);

    jobject arrayList = jenv->NewObject(arrayListClass, alInitMethodId);

    jmethodID alAddMethodId = jenv->GetMethodID(arrayListClass, "add", "(Ljava/lang/Object;)Z");
    assert(alAddMethodId != NULL);

    // init keypoint class
    jclass keypointClass = jenv->FindClass("parallelsurf/Keypoint");
    assert(keypointClass != NULL);

    jmethodID kpInitMethodId = jenv->GetMethodID(keypointClass, "<init>", "(DDDDID[D)V");
    assert(kpInitMethodId != NULL);

    jdoubleArray descriptor = jenv->NewDoubleArray(10);
    assert(descriptor != NULL);

    jdouble vals[10];
    for (int i=0; i < 10; i++) {
        vals[i] = (jdouble) i;
    }

    jenv->SetDoubleArrayRegion(descriptor, 0, 10, vals);

    // create keypoint
    jobject kp = jenv->NewObject(keypointClass, kpInitMethodId,
                                    (jdouble) 1, (jdouble) 2, (jdouble) 3,
                                    (jdouble) 4, (jint) 5, (jdouble) 6,
                                    descriptor);

    // add to arraylist
    jenv->CallBooleanMethod(arrayList, alAddMethodId, kp);
    jenv->DeleteLocalRef(kp);

    return arrayList;
}

Thanks for looking. Your help is much appreciated.

4

1 回答 1

0

Some fine gentleman on the gcc-help mailing list figured this one out:

  • Instead of #pragma GCC java_exceptions to deal with __gxx_personality_v0, make ld link in -l gcc_s
  • If __gcj_personality_v0 is undefined, make ld link in -l gcj
  • Have ld link -l stdc++
  • Ensure that you have libstdc++, libgcjX-dev (X is a version) and libgcc on your machine

If you're linking with g++ (I'm not), some of these may happen automatically (stdc++?)

Also, make sure you didn't forget (or lose) the #import line for the JNI header -- you'll need the extern C {} bits, or you'll get an UnsatisfiedLinkError

于 2011-02-28T00:09:18.917 回答