Question

我是C初学者。经过许多教程后，我不知道为什么我会得到分段错误。我的函数write_new_file和search_by_firstname都出现了这个错误。我认为问题在于我的函数write_new_file中的参数类型PERSON * inrecord。我已经尝试将其从指针更改为inrecord并相应地更改了所有变量，但问题仍然存在。我问过同学们还没有解决方案。

//------TYPEDEFS------
typedef struct{
    char firstname[20];
    char famname[20];
    char pers_number[13]; //yyyymmddnnnc
}PERSON;

void write_new_file(PERSON *inrecord){
    FILE *ptr_myfile;
    ptr_myfile=fopen("test.bin","w");
    if (ptr_myfile==NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }
    strcpy(inrecord->firstname,"Name",20);
    strcpy(inrecord->famname, "surname",20);
    strncpy(inrecord->pers_number, "880192234",13);
    fwrite(&inrecord, sizeof(PERSON), 1, ptr_myfile);
    fclose(ptr_myfile);

}
void search_by_firstname(char *name){
    FILE *ptr_myfile;
    ptr_myfile=fopen("test.bin","r");
    PERSON *temp=NULL;
    if (ptr_myfile==NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }

        fread(temp,sizeof(PERSON),1,ptr_myfile);
        if(strcmp(temp->firstname,name)!=0){
            printf("Not found");
            }else{
               printf("found");
            }

    fclose(ptr_myfile);
}

int main(void){
    PERSON *ppost=NULL;
    write_new_file(ppost);
    search_by_firstname("Neda");
    return(0);
}

Answer 1

您在

中取消NULL指针

void write_new_file(PERSON *inrecord)
{
    FILE *ptr_myfile;

    ptr_myfile = fopen("test.bin","w");
    if (ptr_myfile == NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }
    strcpy(inrecord->firstname, "Name", 20);
    strcpy(inrecord->famname, "surname", 20);
    strncpy(inrecord->pers_number, "880192234", 13);
    fwrite(&inrecord, sizeof(PERSON), 1, ptr_myfile);
    fclose(ptr_myfile);
}

您不需要将指针传递给写文件函数，您需要的是

void write_new_file()
{
    FILE *ptr_myfile;
    PERSON person;

    ptr_myfile = fopen("test.bin","w");
    if (ptr_myfile == NULL)
    {
        printf("Unable to open file!");
        exit(0);
    }
    strcpy(person.firstname, "Name", 20);
    strcpy(person.famname, "surname", 20);
    strncpy(person.pers_number, "880192234", 13);

    fwrite(&person, sizeof(PERSON), 1, ptr_myfile);

    fclose(ptr_myfile);
}

在你的主要你会这样做

int main(void) {
    write_new_file();    
    search_by_firstname("Neda");
    return(0);
}

您没有为temp分配空间，在这里您尝试访问temp
```
 fread(temp,sizeof(PERSON),1,ptr_myfile);
```
但你没有为它分配空间，你也不需要指针，而是
```
 PERSON temp;
 fread(&temp, sizeof(PERSON), 1, ptr_myfile);
```
会做得更好，在尝试取消引用fread()之前，您可能还想检查temp是否成功，否则会导致未定义的行为。

为什么我会出现Segmentation fault（core dumped）？

1 个答案: