c - 错误 : expected ‘:’ , ‘,’、 ‘;’、 ‘}’ 或 ‘__attribute__’

Question

我正在制作一个函数，以链表的形式将文件加载到内存中。但是当我编译代码时，出现错误: error: Expected ':', ',', ';', '}' 或 '__attribute__'

代码如下

加载文件.c:

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

struct node{
    char* data = NULL;
    struct node* next = NULL;
};

struct node* head = NULL;
struct node* tail = NULL;

int load_file(char* file_name){

    char line[1000];
    char* data = NULL;
    struct node* temp = NULL;

    FILE* fp = fopen(file_name,"r");

    if(fp == NULL){
        printf("cannot open the file\n");
        return -1;
    }
    while(fscanf(fp,"%99s",line) == 1){
        data = (char*)malloc(sizeof(char) * strlen(line));
        if(data == NULL){
            printf("could not allocate memory for string\n");
            return -2;
        }

        strcpy(data,line);

        temp = (struct node*)malloc(sizeof(struct node));
        if(temp == NULL){
            printf("could not allocate memory for node\n");
        }
        if(head == NULL){
            head = temp;
            tail = temp;
        }else{
            tail->next = temp;
            tail = tail->next;
        }
    }

    return 0;
}

加载文件.h:

int load_file(char*);

测试.c:

#include<stdio.h>
#include"load_file.h"

int main(){

    char* file= "text.txt";

    printf("ruuning\n");
    load_file(file);
    printf("done");


    return 0;
}

编译时出现错误:

harsh@harsh-Inspiron-3558:~/c/bank_management/include/load_file$ sudo gcc test.c load_file.c -o test
load_file.c:6:13: error: expected ‘:’, ‘,’, ‘;’, ‘}’ or ‘__attribute__’ before ‘=’ token
  char* data = NULL;
             ^
load_file.c: In function ‘load_file’:
load_file.c:42:8: error: ‘struct node’ has no member named ‘next’
    tail->next = temp;
        ^
load_file.c:43:15: error: ‘struct node’ has no member named ‘next’
    tail = tail->next;
               ^

对于任何错误，我们深表歉意。我是初学者。

Answer 1

您无需将初始值设定项添加到类型定义中；改变

struct node{
    char* data = NULL;
    struct node* next = NULL;
};

至

struct node{
  char *data;
  struct node *next;
};

当您创建结构节点的实例时，您将初始化这些字段，如下所示:

struct node foo = {NULL, NULL};

或

struct node foo = { .data = NULL, .next = NULL }; // as of C99

或

struct node foo;
...
foo.data = NULL;
foo.next = NULL;

或

struct node foo;
...
foo = (struct node){.data = NULL, .next = NULL}; // as of C99

或

struct node *foo = malloc( sizeof *foo );
foo->data = NULL;
foo->next = NULL;

或

struct node *foo = malloc( sizeof *foo );
*foo = (struct node){.data = NULL, .next = NULL}; // as of C99

请注意，虽然

struct node *foo = calloc( 1, sizeof *foo );

会将*foo的字段初始化为所有位0，这不一定与将它们初始化为NULL相同 - 所保证的是零值< em>常量表达式相当于NULL，而不是零值运行时表达式。