Play a sound with SDL2 (no SDL_Mixer)

playwav.c

#include <SDL2/SDL.h>

#define MUS_PATH "Roland-GR-1-Trumpet-C5.wav"

// prototype for our audio callback
// see the implementation for more information
void my_audio_callback(void *userdata, Uint8 *stream, int len);

// variable declarations
static Uint8 *audio_pos; // global pointer to the audio buffer to be played
static Uint32 audio_len; // remaining length of the sample we have to play


/*
** PLAYING A SOUND IS MUCH MORE COMPLICATED THAN IT SHOULD BE
*/
int main(int argc, char* argv[]){

	// Initialize SDL.
	if (SDL_Init(SDL_INIT_AUDIO) < 0)
			return 1;

	// local variables
	static Uint32 wav_length; // length of our sample
	static Uint8 *wav_buffer; // buffer containing our audio file
	static SDL_AudioSpec wav_spec; // the specs of our piece of music
	
	
	/* Load the WAV */
	// the specs, length and buffer of our wav are filled
	if( SDL_LoadWAV(MUS_PATH, &wav_spec, &wav_buffer, &wav_length) == NULL ){
	  return 1;
	}
	// set the callback function
	wav_spec.callback = my_audio_callback;
	wav_spec.userdata = NULL;
	// set our global static variables
	audio_pos = wav_buffer; // copy sound buffer
	audio_len = wav_length; // copy file length
	
	/* Open the audio device */
	if ( SDL_OpenAudio(&wav_spec, NULL) < 0 ){
	  fprintf(stderr, "Couldn't open audio: %s\n", SDL_GetError());
	  exit(-1);
	}
	
	/* Start playing */
	SDL_PauseAudio(0);

	// wait until we're don't playing
	while ( audio_len > 0 ) {
		SDL_Delay(100); 
	}
	
	// shut everything down
	SDL_CloseAudio();
	SDL_FreeWAV(wav_buffer);

}

// audio callback function
// here you have to copy the data of your audio buffer into the
// requesting audio buffer (stream)
// you should only copy as much as the requested length (len)
void my_audio_callback(void *userdata, Uint8 *stream, int len) {
	
	if (audio_len ==0)
		return;
	
	len = ( len > audio_len ? audio_len : len );
	//SDL_memcpy (stream, audio_pos, len); 					// simply copy from one buffer into the other
	SDL_memset(stream, 0, len);
	SDL_MixAudio(stream, audio_pos, len, SDL_MIX_MAXVOLUME);// mix from one buffer into another
	
	audio_pos += len;
	audio_len -= len;
}

Great advice for beginners like me , thx!