对STM32库函数中 assert 函数的认知

> 本段代码取自 <stm32f4xx_gpio.c>

> 可以看出进入函数第一件事就是做 assert 输入参数检查，参数合法后，根据参数做相应操作

 /**
   * @brief  Initializes the GPIOx peripheral according to the specified parameters in the GPIO_InitStruct.
   * @param  GPIOx: where x can be (A..K) to select the GPIO peripheral for STM32F405xx/407xx and STM32F415xx/417xx devices
   *                      x can be (A..I) to select the GPIO peripheral for STM32F42xxx/43xxx devices.
   *                      x can be (A, B, C, D and H) to select the GPIO peripheral for STM32F401xx devices.
   * @param  GPIO_InitStruct: pointer to a GPIO_InitTypeDef structure that contains
   *         the configuration information for the specified GPIO peripheral.
   * @retval None
   */
 void GPIO_Init(GPIO_TypeDef* GPIOx, GPIO_InitTypeDef* GPIO_InitStruct)
 {
   uint32_t pinpos = 0x00, pos = 0x00 , currentpin = 0x00;

   /* Check the parameters */
   assert_param(IS_GPIO_ALL_PERIPH(GPIOx));
   assert_param(IS_GPIO_PIN(GPIO_InitStruct->GPIO_Pin));
   assert_param(IS_GPIO_MODE(GPIO_InitStruct->GPIO_Mode));
   assert_param(IS_GPIO_PUPD(GPIO_InitStruct->GPIO_PuPd));

   /* ------------------------- Configure the port pins ---------------- */
   /*-- GPIO Mode Configuration --*/
   for (pinpos = 0x00; pinpos < 0x10; pinpos++)
   {
     pos = ((uint32_t)0x01) << pinpos;
     /* Get the port pins position */
     currentpin = (GPIO_InitStruct->GPIO_Pin) & pos;

     if (currentpin == pos)
     {
       GPIOx->MODER  &= ~(GPIO_MODER_MODER0 << (pinpos * ));
       GPIOx->MODER |= (((uint32_t)GPIO_InitStruct->GPIO_Mode) << (pinpos * ));

       if ((GPIO_InitStruct->GPIO_Mode == GPIO_Mode_OUT) || (GPIO_InitStruct->GPIO_Mode == GPIO_Mode_AF))
       {
         /* Check Speed mode parameters */
         assert_param(IS_GPIO_SPEED(GPIO_InitStruct->GPIO_Speed));

         /* Speed mode configuration */
         GPIOx->OSPEEDR &= ~(GPIO_OSPEEDER_OSPEEDR0 << (pinpos * ));
         GPIOx->OSPEEDR |= ((uint32_t)(GPIO_InitStruct->GPIO_Speed) << (pinpos * ));

         /* Check Output mode parameters */
         assert_param(IS_GPIO_OTYPE(GPIO_InitStruct->GPIO_OType));

         /* Output mode configuration*/
         GPIOx->OTYPER  &= ~((GPIO_OTYPER_OT_0) << ((uint16_t)pinpos)) ;
         GPIOx->OTYPER |= (uint16_t)(((uint16_t)GPIO_InitStruct->GPIO_OType) << ((uint16_t)pinpos));
       }

       /* Pull-up Pull down resistor configuration*/
       GPIOx->PUPDR &= ~(GPIO_PUPDR_PUPDR0 << ((uint16_t)pinpos * ));
       GPIOx->PUPDR |= (((uint32_t)GPIO_InitStruct->GPIO_PuPd) << (pinpos * ));
     }
   }
 }

> 本段代码取自 <stm32f4xx_conf.h>

> 可以看出函数 assert_param(expr) 由宏控制为两个情况， 当要检查的参数表达式为真，则 ((void)0) 什么也不干， 当要检查的参数表达式为假， 则调用函数 assert_failed((uint8_t *)__FILE__, __LINE__) 指出参数表达式错误发生的位置(所在文件， 所在行)

 /* Uncomment the line below to expanse the "assert_param" macro in the
    Standard Peripheral Library drivers code */
 /* #define USE_FULL_ASSERT    1 */

 /* Exported macro ------------------------------------------------------------*/
 #ifdef  USE_FULL_ASSERT

 /**
   * @brief  The assert_param macro is used for function's parameters check.
   * @param  expr: If expr is false, it calls assert_failed function
   *   which reports the name of the source file and the source
   *   line number of the call that failed.
   *   If expr is true, it returns no value.
   * @retval None
   */
   #define assert_param(expr) ((expr) ? (void)0 : assert_failed((uint8_t *)__FILE__, __LINE__))
 /* Exported functions ------------------------------------------------------- */
   void assert_failed(uint8_t* file, uint32_t line);
 #else
   #define assert_param(expr) ((void)0)
 #endif /* USE_FULL_ASSERT */

> 本段代码取自 <stm32f4xx_gpio.h>

> 可以看出作为函数 assert_param(expr)  参数表达式 IS_GPIO_ALL_PERIPH(PERIPH) 是一组判定相等的表达式来检查参数的合法性

 #define IS_GPIO_ALL_PERIPH(PERIPH) (((PERIPH) == GPIOA) || \
                                     ((PERIPH) == GPIOB) || \
                                     ((PERIPH) == GPIOC) || \
                                     ((PERIPH) == GPIOD) || \
                                     ((PERIPH) == GPIOE) || \
                                     ((PERIPH) == GPIOF) || \
                                     ((PERIPH) == GPIOG) || \
                                     ((PERIPH) == GPIOH) || \
                                     ((PERIPH) == GPIOI) || \
                                     ((PERIPH) == GPIOJ) || \
                                     ((PERIPH) == GPIOK))