Question

I am having a bit of trouble with the following code that appears to be causing a segmentation fault at the indicated line. I’m trying to create an array of 8 bit unsigned integers in order to instantiate an OpenCV Mat object with, however the segfault occurs partway through the loop that populates the array.

It appears to happen at a different iteration each time, leading me to suspect that something is getting deallocated by GC, but I can’t determine what.

SignDetector.c

JNIEXPORT void JNICALL Java_org_xxx_detectBlobs(JNIEnv *env, jclass clazz, jintArray in)
{
    jint *contents = (*env)->GetIntArrayElements(env, in, NULL);

    threshold(contents, PIXEL_SAMPLE_RATE);
    detectBlobs(contents);

    (*env)->ReleaseIntArrayElements(env, in, contents, 0);
}

BlobDetector.cpp

void detectBlobs(jint *contents)
{
    LOGD("Call to detectBlobs in BlobDetector.cpp");

    uint8_t *thresholded = (uint8_t*) malloc(frame_size);

    int i;
    for(i = 0; i < frame_size - 1; i++)
        thresholded[i] = (contents[i] == WHITE) ? 0 : 1; // Segfaults partway through this loop.

frame_size is simply the number of pixels in an image, which is also equivalent to the length of the jintArray that the image is passed to native code in.

Any suggestions?

Answer 1

Managed to resolve this by simply restarting my AVD on the Android emulator. Problem appears to not occur on a real device either, so I can only conclude that something exploded in the virtual device’s RAM.