_CrtCheckMemory();
    memset(ci->equ, 3, FIRC*sizeof(eq_t));  // works fine
    _CrtCheckMemory();
    design_filters(ci->fbank, ci->equ, ci->eqs, ksize, fft_size, samplerate, ci->spline_lut[0], &ci->spline_changed, ci->spline_sem, kV, &ci->eqs_count);
        |
        |
        v


void design_filters(filterbank_t *fbank, eq_t *equ, eq_t *eqs, int32_t ksize, int32_t fft_size, double sr, double *spline_lut, int32_t *spline_changed, mutex_t *spline_sem, int32_t kV, int32_t *eqs_countp)
{
    int32_t i, ik, dsize, start, end, eqs_count;
    double half_rolloff, t, tc, p0, p1, p2, p3, slope, dist, pitch, b;
    FILE *file;

    _CrtCheckMemory();
    memset(equ, 2, FIRC*sizeof(eq_t));  // crashes
    _CrtCheckMemory();

...

}