Cout trigger breakpoint when i try to print something which is not a string

Question

I trying to build fft function in c++. I realized there are errors in the process so I wanted to print each step on it's own. When I try to do cout to everything that is not a string it trigger a breakpoint and error: "A heap has been corrupted " In the main it sometimes and sometimes not Any help, or suggestions would be much appreciated.

Edit : Code after fix

complex<double>* fft(complex<double>* signal, int len)
{
    if (len == 1) return signal;
    else
    {
        const complex<double> J(0, 1);
        const double PI = 3.14159265358979323846;
        const double THRESHOLD = 1e-10;
        complex<double> w(1, 0);
        complex<double>* x_d1 = new complex<double>[len / 2];
        complex<double>* x_d2 = new complex<double>[len / 2];
        for (int i = 0; i < len/2; i++)
        {
            x_d1[i] = signal[2*i];
            x_d2[i] = signal[2*i + 1];
        }
        complex<double>* y_1 = fft(x_d1, len / 2);
        complex<double>* y_2 = fft(x_d2, len / 2);
        complex<double>* dft = mergePointers(y_1, y_2, len / 2);
        delete[] x_d1, x_d2, y_1, y_2;
        for (int k = 0; k < len/2; k++)
        {
            complex<double> p = dft[k];
            complex<double> w_k = exp(J * ((-2*PI*k) / len));
            complex<double> q = w_k * dft[k + (len / 2)];
            dft[k] = p + q;
            dft[k + len / 2] = p - q;
            if (abs(dft[k].real()) < THRESHOLD) dft[k] = complex<double>(0, dft[k].imag());
            if (abs(dft[k].imag()) < THRESHOLD) dft[k] = complex<double>(dft[k].real(), 0);
            if (abs(dft[k + (len / 2)].real()) < THRESHOLD) dft[k + (len / 2)] = complex<double>(0, dft[k + (len / 2)].imag());
            if (abs(dft[k + (len / 2)].imag()) < THRESHOLD) dft[k + (len / 2)] = complex<double>(dft[k + (len / 2)].real(), 0);
        }
        return dft;
    }
}

Answer 1

You allocated dynamically arrays with len / 2 elements. But in for loops like this

for ( int i = 0; i <= len/2; i++ )

you are trying to access len / 2 + 1 elements that results in undefined behavior. The valid range of indices is [0, len / 2 ).

You have to write

for ( int i = 0; i < len/2; i++ )