// working
char* AUDIO_GetFile(FIL* fil, DIR* dir, FILINFO* fno) {
    FRESULT res;
    res = f_readdir(dir, fno); /* Read a directory item */
    if (fno->fname[0] == '\0')} /* End of files */
       ...
    }
    ...
    return &(fno->fname);
}

// working
char* AUDIO_GetFile(FIL* fil, DIR* dir, FILINFO* fno) {
    FRESULT res;
	FILINFO t_fno;
    res = f_readdir(dir, &t_fno); /* Read a directory item */
    if (t_fno.fname[0] == '\0')} /* End of files */
       ...
    }
    ...
    return &(fno->fname);
}

// not working
char* AUDIO_GetFile(FIL* fil, DIR* dir, FILINFO* fno) {
    FRESULT res;
	FILINFO *t_fno = NULL;
    res = f_readdir(dir, t_fno); /* Read a directory item */
    if (t_fno->fname[0] == '\0')} /* End of files */
       ...
    }
    ...
    return &(fno->fname);
}