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c - 零填充字符串发出警告但仍然有效

转载 作者：太空宇宙 更新时间：2023-11-04 01:45:34 25 4
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长话短说:

  • 编译器发出警告。行为未定义。
  • 但由于undefined 行为对公司有利，因此试图找到纠正它的可靠理由(更改 100 行代码，需要说服经理)

sprintf 警告

'0' flag used with ‘%s’ gnu_printf format

根据 this，此行为未定义所以问题/答案。

但在带有 SW4STM32 工具链 (system workbench) 的 arm-gcc 中，零会根据需要进行填充。

MCVE

  1. 对于STM32

下面的代码适用于嵌入式系统，要编译它，您需要提供的工具链 here .对于剩余的文件，请转到 here .

#include "stm32f4xx_hal.h"
#include "stm32f4_discovery.h"

/* Private define ------------------------------------------------------------*/
#define TXBUFFERSIZE 100

/* Definition for USARTx clock resources */
#define USARTx                           USART2
#define USARTx_CLK_ENABLE()              __USART2_CLK_ENABLE();
#define USARTx_RX_GPIO_CLK_ENABLE()      __GPIOA_CLK_ENABLE()
#define USARTx_TX_GPIO_CLK_ENABLE()      __GPIOA_CLK_ENABLE() 

#define USARTx_FORCE_RESET()             __USART2_FORCE_RESET()
#define USARTx_RELEASE_RESET()           __USART2_RELEASE_RESET()

/* Definition for USARTx Pins */
#define USARTx_TX_PIN                    GPIO_PIN_2
#define USARTx_TX_GPIO_PORT              GPIOA  
#define USARTx_TX_AF                     GPIO_AF7_USART2
#define USARTx_RX_PIN                    GPIO_PIN_3
#define USARTx_RX_GPIO_PORT              GPIOA 
#define USARTx_RX_AF                     GPIO_AF7_USART2

/* Private variables ---------------------------------------------------------*/
/* UART handler declaration */
UART_HandleTypeDef UartHandle;

/* Private function prototypes -----------------------------------------------*/
static void SystemClock_Config(void);
static void Error_Handler(void)
static void UART_Init(void);

/* Private functions ---------------------------------------------------------*/
int main(void)
{
    HAL_Init();

    /* Configure the system clock to 168 Mhz */
    SystemClock_Config();

    UART_Init();

    char pkt_buff[TXBUFFERSIZE+2];
    memset(pkt_buff, 0, sizeof(pkt_buff));
    sprintf(pkt_buff, "#%010s,%010s,%020s,%060s\r", "1", "2", "3", "4");
    if(HAL_UART_Transmit(&UartHandle, (uint8_t*)pkt_buff, TXBUFFERSIZE, 5000)!= HAL_OK)
    {
        Error_Handler();   
    }

    while(1) {

    }
}

static void UART_Init(void)
{
    /*##-1- Configure the UART peripheral ######################################*/
    /* Put the USART peripheral in the Asynchronous mode (UART Mode) */
    /* UART1 configured as follow:
    - Word Length = 8 Bits
    - Stop Bit = One Stop bit
    - Parity = None
    - BaudRate = 9600 baud
    - Hardware flow control disabled (RTS and CTS signals) */
    UartHandle.Instance        = USARTx;
    UartHandle.Init.BaudRate   = 9600;
    UartHandle.Init.WordLength = UART_WORDLENGTH_8B;
    UartHandle.Init.StopBits   = UART_STOPBITS_1;
    UartHandle.Init.Parity     = UART_PARITY_NONE;
    UartHandle.Init.HwFlowCtl  = UART_HWCONTROL_NONE;
    UartHandle.Init.Mode       = UART_MODE_TX_RX;
    if(HAL_UART_Init(&UartHandle) != HAL_OK)
    {
        Error_Handler();
    }
}

/**
 * @brief  System Clock Configuration
 *         The system Clock is configured as follow : 
 *            System Clock source            = PLL (HSE)
 *            SYSCLK(Hz)                     = 168000000
 *            HCLK(Hz)                       = 168000000
 *            AHB Prescaler                  = 1
 *            APB1 Prescaler                 = 4
 *            APB2 Prescaler                 = 2
 *            HSE Frequency(Hz)              = 8000000
 *            PLL_M                          = 8
 *            PLL_N                          = 336
 *            PLL_P                          = 2
 *            PLL_Q                          = 7
 *            VDD(V)                         = 3.3
 *            Main regulator output voltage  = Scale1 mode
 *            Flash Latency(WS)              = 5
 * @param  None
 * @retval None
 */
static void SystemClock_Config(void)
{
    RCC_ClkInitTypeDef RCC_ClkInitStruct;
    RCC_OscInitTypeDef RCC_OscInitStruct;

    /* Enable Power Control clock */
    __PWR_CLK_ENABLE();

    /* The voltage scaling allows optimizing the power consumption when the device is 
    clocked below the maximum system frequency, to update the voltage scaling value 
    regarding system frequency refer to product datasheet.  */
    __HAL_PWR_VOLTAGESCALING_CONFIG(PWR_REGULATOR_VOLTAGE_SCALE1);

    /* Enable HSE Oscillator and activate PLL with HSE as source */
    RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
    RCC_OscInitStruct.HSEState = RCC_HSE_ON;
    RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
    RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
    RCC_OscInitStruct.PLL.PLLM = 8;
    RCC_OscInitStruct.PLL.PLLN = 336;
    RCC_OscInitStruct.PLL.PLLP = RCC_PLLP_DIV2;
    RCC_OscInitStruct.PLL.PLLQ = 7;
    if(HAL_RCC_OscConfig(&RCC_OscInitStruct) != HAL_OK)
    {
    Error_Handler();
    }

    /* Select PLL as system clock source and configure the HCLK, PCLK1 and PCLK2 
    clocks dividers */
    RCC_ClkInitStruct.ClockType = (RCC_CLOCKTYPE_SYSCLK | RCC_CLOCKTYPE_HCLK | RCC_CLOCKTYPE_PCLK1 | RCC_CLOCKTYPE_PCLK2);
    RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
    RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
    RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV4;  
    RCC_ClkInitStruct.APB2CLKDivider = RCC_HCLK_DIV2;  
    if(HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_5) != HAL_OK)
    {
    Error_Handler();
    }
}

static void Error_Handler(void)
{
     while(1){}
}

以上代码将通过 UART 传输数据，然后使用 PC-USB 收发器读取数据。上面代码的输出是

#0000000001,0000000002,00000000000000000003,000000000000000000000000000000000000000000000000000000000004

如您所见，即使发出了警告，代码的执行/行为也符合程序员的要求。

这是一个遗留代码，这个错误已经写到很多地方。所以我要修复它，必须修复许多行。但由于代码按预期执行，经理不想更改代码。

问题

  • 代码的行为符合程序员的预期，即使它是未定义。这种未定义的行为在未来是否会改变以破坏代码。
  • 我可以提出什么理由让他们修复这个错误？

25 4 0
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