Question

我正在尝试读取文本文件并将数据存储在struct数组中，但是我遇到了分段错误。这是我的代码：

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

typedef struct{
    char name[24];
    unsigned short value;
}Flags;

int ReadData(char * filename, Flags* retv){

    //First getting the number of lines, this helps to allocate the memory for the struct    
    char line[255];
    int linenr = 0;    
    char* token;    

    FILE* myfile = fopen(filename, "r");
    while(!feof(myfile))
    {
        char ch = fgetc(myfile);
        if(ch == '\n')
        {
            linenr++;
        }
    }
    retv = malloc(linenr * sizeof(Flags));    
    linenr = 0; 

    // Bring the file pointer to the beginning
    rewind(myfile); 

    // Read data line by line
    while (fgets(line, sizeof(line), myfile)) {                
        token = strtok(line, "="); 
        if (token != NULL){            
            strcpy(retv[linenr].name, token);


            // Getting the value
            token = strtok(NULL, "=");
            if (token != NULL)
                retv[linenr].value = atoi(token);
            else
                retv[linenr].value = 0;

            // Debugging
#ifdef DEBUG           
            printf("i: %d\n", linenr);
            printf("Name: %s\n", retv[linenr].name);        
            printf("Value: %d\n", retv[linenr].value);       
#endif
            linenr ++;         
        }   
    }

    fclose(myfile);

    return linenr;
}

int main(int argc, char const *argv[])
{
    Flags * values;
    int linenr = 0;
    int i;

    // Read the data
    linenr = ReadData("test.txt", values);

    // Some debugging
    printf("Line number: %d\n", linenr);

    for (i = 0; i < linenr; i++)
    {
        printf("i: %d\n", i);
        printf("Name: %s\n", values[i].name);
        printf("Value: %d\n", values[i].value);
    }    
    free(values);
    return 0;
}

输出是：

i: 0
Name: fa_flag 
Value: 0
i: 1
Name: s2s_flag 
Value: 12
i: 2
Name: torque_flag 
Value: 1
i: 3
Name: torque_flag2 
Value: 1
i: 4
Name: torque_flag3 
Value: 1
Line number: 5
i: 0
Name: (null)
Segmentation fault (core dumped)

我无法弄清楚我在哪里弄错了。

Answer 1

问题在于：

int ReadData(char * filename, Flags* retv){
    ....
    retv = malloc(linenr * sizeof(Flags));

正确分配内存，但main中的指针未更新。

Flags * values;
....
linenr = ReadData("test.txt", values);

将其更改为：

int ReadData(char * filename, Flags** retv){
    ....
    *retv = malloc(linenr * sizeof(Flags));

和

Flags * values;
....
linenr = ReadData("test.txt", &values);

如何检索struct数组的地址？

1 个答案: