Bug in Android C++/C debugger, incorrect argument values

问题

I have recently encountered a really weird problem while debugging C/C++ application in Android Studio.

I am using Android Studio 3.0

Here is my JNI Call

JNIEXPORT jshortArray JNICALL
Java_net_crosp_android_library_ecgaudioprocessor_EcgSignalProcessorDemodulator_demodulate(
        JNIEnv *env, jobject instance, jshortArray readBuffer_) {

    /* get size of the array */
    jsize len = env->GetArrayLength(readBuffer_);
    int sample_rate = 44100;
    int kd = 12;
    SignalConfiguration signal_cfg = {sample_rate, kd, 1700, sample_rate, sample_rate / kd, 200};
    ECGFMDemodulator *ecg_fm_demodulator = new ECGFMDemodulator();
    ecg_fm_demodulator->set_cfg(signal_cfg);
    ECGFMDemodulator *ecg_fm_demodulator2 = new ECGFMDemodulator(signal_cfg);

    /* get the body of array; it will be referecende by C pointer */
    jshort *body = env->GetShortArrayElements(readBuffer_, JNI_FALSE);

    env->ReleaseShortArrayElements(readBuffer_, body, JNI_COMMIT);
    return readBuffer_;
}

Class ECGFMDemodulator

class ECGFMDemodulator {
private:
    SignalConfiguration m_signal_configuration_;
public:

    ECGFMDemodulator(SignalConfiguration configuration);

    void set_cfg(SignalConfiguration param);
};

And implementation

ECGFMDemodulator::ECGFMDemodulator(SignalConfiguration configuration) {
    this->m_signal_configuration_ = configuration;
    std::cout.rdbuf(new Androidbuf);
    // Print values
    std::cout << "------ VALUES OF CONFIGURATION --------" << std::endl;
    std::cout << "Sample rate : " << this->m_signal_configuration_.sample_rate << std::endl;
    std::cout << "KD : " << this->m_signal_configuration_.kd << std::endl;
    std::cout << "FC : " << this->m_signal_configuration_.fc << std::endl;
    std::cout << "FS : " << this->m_signal_configuration_.fs << std::endl;
    std::cout << "FS2 : " << this->m_signal_configuration_.fs2 << std::endl;
    delete std::cout.rdbuf(0);
    this->init_filters();
}

void ECGFMDemodulator::set_cfg(SignalConfiguration param) {
    this->m_signal_configuration_ = param;
}

I am creating an object like that

int sample_rate = 44100;
int kd = 12;
SignalConfiguration signal_cfg = {sample_rate, kd, 1700, sample_rate, sample_rate / kd, 200};
ECGFMDemodulator *ecg_fm_demodulator = new ECGFMDemodulator();
ecg_fm_demodulator->set_cfg(signal_cfg);
ECGFMDemodulator *ecg_fm_demodulator2 = new ECGFMDemodulator(signal_cfg);

And while debugging I got interesting results

Creating signal_cfg, as you can see values are valid

Watching values in the constructor, as you can see values are random

After creating this object, values are correct and printed to console with valid values. However in debugger they are still garbage.

I/std: ------ VALUES OF CONFIGURATION --------
I/std: Sample rate : 44100
I/std: KD : 12
I/std: FC : 1700
I/std: FS : 44100
I/std: FS2 : 3675

I have also tried to use lldb but got the same values, that are not valid. I've also tried to pass by reference, but got the same result.

(lldb) frame variable
(ECGFMDemodulator *) this = 0xb7688d29
(SignalConfiguration) param = (sample_rate = -1217884423, kd = -1204349992, fc = -1217887850, fs = -1982518100, fs2 = -1983635321, delay = 36)

What is wrong with debugger, I am not able to debug my program, because I am not sure that values being displayed are valid.

Does anyone experiencing similar problems ?

I would be grateful for any help.

Thanks

来源：https://stackoverflow.com/questions/47389139/bug-in-android-c-c-debugger-incorrect-argument-values

标签

android