嵌入式 C 编程必备(9)：sizeof运算符的深度解析与应用

printf("Size of int: %zu bytes\n", sizeof(int));
printf("Size of char: %zu bytes\n", sizeof(char));

int num;
printf("Size of num: %zu bytes\n", sizeof(num));

#include <stdio.h>

int main() {
    float sensorData[200];
    printf("Size of sensorData array: %zu bytes\n", sizeof(sensorData));
    // 假设float为4字节，输出应为800字节
    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    char id[5];
    int value;
    float ratio;
} DeviceInfo;

int main() {
    DeviceInfo *info = (DeviceInfo *)malloc(sizeof(DeviceInfo));
    if (info != NULL) {
        strcpy(info->id, "001");
        info->value = 100;
        info->ratio = 1.5f;
        printf("Allocated memory for DeviceInfo: %zu bytes\n", sizeof(DeviceInfo));
        // 释放内存
        free(info);
    } else {
        printf("Memory allocation failed\n");
    }
    return 0;
}

#include <stdio.h>
#include <string.h>

typedef struct {
    char startFlag;
    short dataLen;
    int payload;
} DataPacket;

void sendData(const char *data, size_t length) {
    // 模拟发送数据，这里仅打印数据长度和实际数据
    printf("Sending %zu bytes: ", length);
    for (size_t i = 0; i < length; i++) {
        printf("%02X ", (unsigned char)data[i]);
    }
    printf("\n");
}

int main() {
    DataPacket packet;
    packet.startFlag = 0x01;
    packet.dataLen = sizeof(packet.payload); // 仅发送payload的长度作为示例
    packet.payload = 12345;

    // 发送数据包大小（这里仅作为示例，实际通信中可能需要更复杂的协议）
    sendData((const char *)&packet.dataLen, sizeof(packet.dataLen));
    // 发送完整数据包（包括startFlag、dataLen和payload）
    sendData((const char *)&packet, sizeof(packet));

    return 0;
}

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct {
    unsigned int baudRate;
    char parity;
    unsigned char stopBits;
} SerialConfig;

// 模拟写入EEPROM的函数（实际中应使用EEPROM驱动库）
void writeEEPROM(size_t address, const char *data, size_t length) {
    // 这里仅打印写入的信息，实际中应写入EEPROM
    printf("Writing to EEPROM at address %zu: ", address);
    for (size_t i = 0; i < length; i++) {
        printf("%02X ", (unsigned char)data[i]);
    }
    printf("\n");
}

int main() {
    SerialConfig config = {9600, 'N', 1};
    writeEEPROM(0, (const char *)&config, sizeof(config));
    return 0;
}

#include <stdio.h>

typedef struct {
    char a;      // 1字节
    int b;       // 4字节（可能因对齐而占用更多空间）
    short c;      // 2字节
} TestStruct1;

typedef struct {
    char a;      // 1字节
    short c;      // 2字节（紧跟char，减少对齐浪费）
    int b;       // 4字节
} TestStruct2;

int main() {
    printf("Size of TestStruct1: %zu bytes\n", sizeof(TestStruct1));
    printf("Size of TestStruct2: %zu bytes\n", sizeof(TestStruct2));
    // 比较两个结构体的大小，观察内存对齐的影响
    return 0;
}

#include <stdio.h>

int main() {
    printf("Size of char: %zu byte\n", sizeof(char));
    printf("Size of short: %zu bytes\n", sizeof(short));
    printf("Size of int: %zu bytes\n", sizeof(int));
    printf("Size of long: %zu bytes\n", sizeof(long));
    printf("Size of float: %zu bytes\n", sizeof(float));
    printf("Size of double: %zu bytes\n", sizeof(double));
    // 根据需要添加更多数据类型的打印
    return 0;
}

#include <stdio.h>
 
void printArraySize(int arr[]) {
    printf("Size of array in function: %zu bytes\n", sizeof(arr)); // 错误：这将打印指针的大小
}
 
int main() {
    int myArray[10];
    printf("Size of array in main: %zu bytes\n", sizeof(myArray)); // 正确：这将打印数组的实际大小
    printArraySize(myArray);
    return 0;
}

#include <stdio.h>

int main() {
    int *intPtr;
    char *charPtr;
    printf("Size of int pointer: %zu bytes\n", sizeof(intPtr)); // 通常是4或8字节
    printf("Size of char pointer: %zu bytes\n", sizeof(charPtr)); // 同样是4或8字节
    return 0;
}

#include <stdio.h>

typedef struct {
    char a;
    int b;
    char c;
} Struct1;

typedef struct {
    char a;
    char c;
    int b;
} Struct2;

int main() {
    printf("Size of Struct1: %zu bytes\n", sizeof(Struct1)); // 可能比预期大，因为内存对齐
    printf("Size of Struct2: %zu bytes\n", sizeof(Struct2)); // 可能更紧凑
    return 0;
}