malloc: error for object: pointer being freed was not allocated

Question

so I made a JNI wrapper for an MSER in OpenCv v2.4.13.2.

I receive this error after about 5 minutes leaving the Java process running:

java(658,0x7000070bb000) malloc: *** error for object 0x11921c6f0: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug

This is most definitely from the use of JNI, but I'm unsure of what exactly is causing this malloc error as I am not terribly familiar with C++. I'm guessing it's due to improper memory clearing, but am unsure of where.

Relevant code from my file:

MSER mser; // Global variable so that pointer useable by Java can be created

JNIEXPORT jlong JNICALL Java_org_opencv_features2d_MSER_create_11(JNIEnv* env, jclass cls, jint delta, jint min_area, jint max_area, jdouble max_variation, jdouble min_diversity, jint max_evolution, jdouble area_threshold, jdouble min_margin, jint edge_blur_size)
{
    static const char method_name[] = "MSSR::create_1";

    //LOGD("%s", method_name);

    mser = MSER::MSER(delta, min_area, max_area, max_variation, min_diversity, max_evolution, area_threshold, min_margin, edge_blur_size);

    return (jlong) &mser;
}

JNIEXPORT void JNICALL Java_org_opencv_features2d_MSER_detect_14(JNIEnv* env, jobject thiz, jlong self, jlong image_addr, jlong msers_addr, jlong mask_addr)
{
    static const char method_name[] = "MSSR::detect_4";

    try {
        //LOGD("%s", method_name);
        MSER* me = (MSER*) self;
        Mat image = *(Mat*) image_addr;
        vector<vector<Point> > msers; // List<MatOfPoint> -> Mat -> vector<vector<Point> >
        Mat mask = *(Mat*) mask_addr;
        me->operator()(image, msers, mask);
        vector_vector_Point_to_Mat(msers, *(Mat*)msers_addr); // Store vector data in Mat dummy to be converted to List<MatOfPoint>
    }
    catch (const exception &e) {
        throwJavaException(env, &e, method_name);
    }
    catch (...) {
        throwJavaException(env, 0, method_name);
    }
}

And from converters.cpp:

#define CHECK_MAT(cond) if(!(cond)){ return; }

void vector_vector_Point_to_Mat(std::vector< std::vector< Point > >& vv_pt, Mat& mat)
{
    std::vector<Mat> vm;
    vm.reserve( vv_pt.size() );
    for(size_t i=0; i<vv_pt.size(); i++)
    {
        Mat m;
        vector_Point_to_Mat(vv_pt[i], m);
        vm.push_back(m);
    }
    vector_Mat_to_Mat(vm, mat);
}

void vector_Mat_to_Mat(std::vector<cv::Mat>& v_mat, cv::Mat& mat)
{
    int count = (int)v_mat.size();
    mat.create(count, 1, CV_32SC2);
    for(int i=0; i<count; i++)
    {
        long long addr = (long long) new Mat(v_mat[i]);
        mat.at< Vec<int, 2> >(i, 0) = Vec<int, 2>(addr>>32, addr&0xffffffff);
    }
}

This also only seems to happen when I have multiple instances of the same program running. That probably means it has something to do with the global MSER mser variable.

Thanks in advance,
Kira

Oo.oO Oo.oO · Accepted Answer · 2017-05-20T19:02:38

Try to use gdb and check the back trace inside:

malloc_error_break

You can find information on how to debug JNI + Java here:

http://jnicookbook.owsiak.org/recipe-No-D001/

http://jnicookbook.owsiak.org/recipe-No-D002/

You can also take a look at demo movie here:

https://youtu.be/8Cjeq4l5COU

In case you can't use CLion and you have to stick to gdb, take a look here on how to debug Java + native code:

http://www.owsiak.org/?p=2095

Basically, what you can do is to:

start JVM in debug mode
attach to JVM using gdb
inside gdb set breakpoint to: malloc_error_break

break malloc_error_break

once breakpoint is hit, take a look at back trace and see what was called just before malloc_error_break was hit

Have fun with JNI!

malloc: error for object: pointer being freed was not allocated

1 Answers