c-为什么我会出现分段错误(核心转储)

Question

我是一个C初学者。在经历了许多教程之后，我不确定为什么我会出现分割错误。我在函数write_new_file和search_by_firstname上都出现了此错误。我认为问题出在我的函数write_new_file中记录的参数类型PERSON*中。我已经尝试将它从指针更改为inrecord，并相应地更改了所有变量，但问题仍然存在。我已经问过同学了，但还没有解决办法。

//------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

1. 您在中丢弃了一个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);
   }
   

   您不需要向写入文件函数传递指针，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);
   }
   

   你主要会做这个

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

2. 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);
   

   但您并没有为它分配空间，这里也不需要指针，而是

    PERSON temp;
    fread(&temp, sizeof(PERSON), 1, ptr_myfile);
   

   如果做得更好，您可能还想在尝试取消引用temp之前检查fread()是否成功，因为否则会导致未定义的行为。