Semihosting output is garbled

int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration--------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* USER CODE BEGIN Init */

  /* USER CODE END Init */

  /* Configure the system clock */
  SystemClock_Config();

  /* USER CODE BEGIN SysInit */

  /* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  /* USER CODE BEGIN 2 */
  printf("Hello semihosting!\n");
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */
    printf("Hello semihosting!\n");
    /* USER CODE BEGIN 3 */
  }
  /* USER CODE END 3 */
}

  # List different hardware targets that are used to deploy the solution.
  target-types:
    - type: STM32F407VETx
      device: STM32F407VETx
      target-set:
        - set:
          images:
            - project-context: Project.Debug
          debugger:
            name: ST-Link@pyOCD
            clock: 4000000
            protocol: swd
            telnet:
              - mode: monitor

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