PortAudio passthrough with callback

/* g++ -std=c++11 -l portaudio -o port-dsp-callback port-dsp-callback.cpp */

#include <cstdint>
#include <cstring>
#include <iostream>
#include <portaudio.h>

/*
 * Log a PaError to console.
 */
static void log_pa (PaError err) {
    std::cout << "PortAudio: " << Pa_GetErrorText(err) << std::endl;
}

/*
 * Callback for PortAudio.
 */
static int callback (const void* input_buffer, void* output_buffer,
            unsigned long frames_per_buffer, const PaStreamCallbackTimeInfo* time_info,
            PaStreamCallbackFlags status_flags, void* user_data) {
    /* Since we only use memcpy, these casts are not strictly neccessary. */
    std::int32_t* out = (std::int32_t*)output_buffer;
    std::int32_t* in = (std::int32_t*)input_buffer;
    (void)user_data;
    std::memcpy(out, in, sizeof(std::int32_t) * frames_per_buffer);
    return paContinue;
}

/*
 * Program entry point.
 */
int main (int argc, char** argv) {
    /* Initialize. */
    log_pa(Pa_Initialize());
    PaStreamParameters input_parameters, output_parameters;

    /* Set input parameters. */
    input_parameters.device = Pa_GetDefaultInputDevice();
    input_parameters.channelCount = 1;
    input_parameters.sampleFormat = paInt32;
    const PaDeviceInfo* input_info = Pa_GetDeviceInfo(input_parameters.device);
    input_parameters.suggestedLatency = input_info->defaultLowInputLatency;
    input_parameters.hostApiSpecificStreamInfo = NULL;

    /* Set output parameters. */
    output_parameters.device = Pa_GetDefaultOutputDevice();
    output_parameters.channelCount = 1;
    output_parameters.sampleFormat = paInt32;
    const PaDeviceInfo* output_info = Pa_GetDeviceInfo(output_parameters.device);
    output_parameters.suggestedLatency = output_info->defaultLowOutputLatency;
    output_parameters.hostApiSpecificStreamInfo = NULL;

    /* Create and start stream, let it run for 5 seconds, then close it again. */
    PaStream* stream = NULL;
    log_pa(Pa_OpenStream(&stream, &input_parameters, &output_parameters, 96000, paFramesPerBufferUnspecified, paNoFlag, callback, NULL));
    log_pa(Pa_StartStream(stream));
    Pa_Sleep(5000);
    log_pa(Pa_StopStream(stream));
    log_pa(Pa_CloseStream(stream));
    log_pa(Pa_Terminate());
    return 0;
}