Ext Interrupt works fine in dedicated project, but does not when copied into the main project

[Tobe]

I have this code, in where the interrupt works without issues in debug mode:

void EXTI2_IRQHandler(){
	SET_BIT(EXTI->PR1, EXTI_PR1_PIF2); //  Clear interrupt flag
}

/* USER CODE END 0 */

/**
  * @brief  The application entry point.
  * @retval int
  */
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 */


  __HAL_RCC_GPIOD_CLK_ENABLE();
  GPIO_InitTypeDef my_GPIO_InitStruct = {0};
  // enable nFault (PD2)
  my_GPIO_InitStruct.Pin = GPIO_PIN_2;
  my_GPIO_InitStruct.Mode = GPIO_MODE_IT_FALLING;
  my_GPIO_InitStruct.Pull = GPIO_PULLUP;
  HAL_GPIO_Init(GPIOD, &my_GPIO_InitStruct);

  // Interrupt for nFault (PD2)
  SET_BIT(EXTI->IMR1, EXTI_IMR1_IM2);		// interrupt for EXTI line 2 (PD2)
  SET_BIT(EXTI->FTSR1, EXTI_FTSR1_FT2);	// Falling edge for line 2 (PD2)
  SET_BIT(SYSCFG->EXTICR[0] ,SYSCFG_EXTICR1_EXTI2_PD); // Interrupt configuration for PD2

  NVIC_EnableIRQ(EXTI2_IRQn);

  SET_BIT(EXTI->SWIER1, EXTI_SWIER1_SWI2); // trigger interrupt


  while(1);

 But when put into the main project, it gives me an error, as if the interrupt routine was never defined.

[Tobe · Accepted solution]

Found the solution already:

I have copied the routine in another file. I put the declaration too, but it didnt work.

It workes like this (adding the extern "C"):

#ifdef __cplusplus
 extern "C" {
#endif

void EXTI2_IRQHandler(void);

#ifdef __cplusplus
}
#endif