C程序编译报错求助：解决[-Waddress]与[-Wpointer-arith]警告

编译错误说明 #

遇到的编译错误分为两类：

• comparison with string literal results in unspecified behavior [-Waddress]：直接用==比较字符串指针与字面量，C语言中==比较的是指针地址而非字符串内容，属于错误用法。
• pointer of type 'void *' used in arithmetic [-Wpointer-arith]：void*指针无法直接做算术运算，编译器无法确定其指向数据的类型大小，无法计算偏移量。

具体修改点 #

1. 修复字符串比较错误 #

将所有structure == "xxx_t"的判断替换为strcmp(structure, "xxx_t") == 0，strcmp是C标准库专门用于字符串内容比较的函数，返回0代表两个字符串相等。

2. 修复void*指针算术运算错误 #

不要直接对void*类型的table指针做加法，改用count变量计算当前元素索引，通过数组下标方式访问结构体，避免指针运算错误。

修改后的完整代码 #

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

// Define the structure for table1
typedef struct {
    char customer_code[31];
    char firstname[101];
    char lastname[101];
} table1_t;

// Define the structure for table2
typedef struct {
    char customer_code[31];
    char invoice_code[31];
    float amount;
    char date[11]; // Assuming DATE is in 'YYYY-MM-DD' format
} table2_t;

// Define the structure for table3
typedef struct {
    char invoice_code[31];
    char item_code[31];
    float amount;
    int quantity;
} table3_t;

// Define the structure for table4
typedef struct {
    char customer_code[31];
} table4_t;

int rows;

// Function to read CSV file and populate the table name passed
int parse_csv(const char *filename, void *table, const char *structure) {
    FILE *fp = fopen(filename, "r");
    if (!fp) {
        perror("Error opening file");
        return -1;
    }

    // Skip the first record
    char line[4096];
    fgets(line, sizeof(line), fp);

    int count = 0;
    while (fgets(line, sizeof(line), fp)) {
        if (strcmp(structure, "table1_t") == 0) {
            table1_t *t1 = (table1_t *)table + count;
            sscanf(line, "%[^,],%[^,],%s", t1->customer_code, t1->firstname, t1->lastname);
        } else if (strcmp(structure, "table2_t") == 0) {
            table2_t *t2 = (table2_t *)table + count;
            sscanf(line, "%[^,],%[^,],%f,%s", t2->customer_code, t2->invoice_code, &t2->amount, t2->date);
        } else if (strcmp(structure, "table3_t") == 0) {
            table3_t *t3 = (table3_t *)table + count;
            sscanf(line, "%[^,],%[^,],%f,%d", t3->invoice_code, t3->item_code, &t3->amount, &t3->quantity);
        } else if (strcmp(structure, "table4_t") == 0) {
            table4_t *t4 = (table4_t *)table + count;
            sscanf(line, "%[^,]", t4->customer_code);
        } else {
            fprintf(stderr, "Invalid table structure\n");
            fclose(fp);
            return -1;
        }
        count++;
    }

    fclose(fp);
    return count;
}

int main() {
    // Process table1
    table1_t table1[500000];
    rows = parse_csv("table1.csv", table1, "table1_t");
    printf("Number of rows in table1: %d\n", rows);

    //Process table2
    table2_t table2[1000000];
    rows = parse_csv("table2.csv", table2, "table2_t");
    printf("Number of rows in table2: %d\n", rows);

    //Process table3
    table3_t table3[5000000];
    rows = parse_csv("table3.csv", table3, "table3_t");
    printf("Number of rows in table3: %d\n", rows);   

    //Process table4
    table4_t table4[1000];
    rows = parse_csv("table4.csv", table4, "table4_t");
    printf("Number of rows in table4: %d\n", rows);   

    return 0;
}

额外说明 #

• (table1_t *)table + count的写法，是将void*转换为结构体指针后，指针加法会自动按结构体大小计算偏移量，比直接操作void*更安全。
• 当前sscanf的%[^,]格式符只能处理无引号包裹的简单CSV字段，如果需要处理包含逗号的带引号字段，建议使用专门的CSV解析库。

内容的提问来源于stack exchange，提问作者Tom