Segfault同时将文本文件读入结构指针

Question

我正在编写一个代码来计算jedi名称，它是名字和姓氏的组合。我编写了整个代码并在while循环中获得了分段错误。

以下是代码。它分为标题和C文件：

Structures.h

//void jediName(char *first_name, char *last_name, char buffer[10]);
//void jediName(struct Names Name_Param);
//void * allocate(unsigned int size);
//void * deallocate(void *, int size);

int heap_usage = 0;

struct Names{
    char *first_name;
    char *last_name;
    char *jedi_name;
};

struct Names *name;

void jediName(struct Names *Name_Param);
void * allocate(unsigned int size);
void * deallocate(void *, int size);

Program.c

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

#include "Structures.h"

int main(){

//  char fname[10];
//  char lname[10];
//  char buff[10]= "";
    char buffer1[250];
    char buffer2[250];

    FILE * fp;
/*
        printf("Enter the first & last name : \n");
        scanf("%s %s", buffer1, buffer2 );

    fp = fopen("names.txt", "a");
    fprintf(fp, "\n%s %s", buffer1, buffer2);
    fclose(fp);
*/

    fp = fopen("names.txt","r");
    name->first_name == allocate(10);
    name->last_name == allocate(10);
    name->jedi_name == allocate(10);

    while(!feof(fp)){
        fscanf(fp, "%s %s", name->first_name, name->last_name);
        jediName(name);
//      jediName(name->first_name, name->last_name, name->jedi_name);
        printf("%s %s %s", name->first_name, name->last_name);
    }
    deallocate(name->first_name, 10);
        deallocate(name->last_name, 10);
        deallocate(name->jedi_name, 10);

    fclose(fp);

    return 0;
}

/*
void jediName(char *first_name, char *last_name, char buffer[10]){
    if(strlen(first_name)<2 || strlen(last_name)<3)
        printf("Name of %s %s is too short to compute a jedi name\n", first_name, last_name);
    else{
        buffer[0] = last_name[0];
            buffer[1] = last_name[1];
            buffer[2] = last_name[2];
            buffer[3] = first_name[0];
            buffer[4] = first_name[1];
            printf("Jedi Name for %s %s is %s\n", first_name, last_name, buffer);
    }

    return;
}
*/

void jediName(struct Names *Name_Param){
        if(strlen(Name_Param->first_name)<2 || strlen(Name_Param->last_name)<3)
                printf("Name of %s %s is too short to compute a jedi name\n", Name_Param->first_name, Name_Param->last_name);
        else{
                Name_Param->jedi_name[0] = Name_Param->last_name[0];
                Name_Param->jedi_name[1] = Name_Param->last_name[1];
                Name_Param->jedi_name[2] = Name_Param->last_name[2];
                Name_Param->jedi_name[3] = Name_Param->first_name[0];
                Name_Param->jedi_name[4] = Name_Param->first_name[1];
                printf("Jedi Name for %s %s is %s\n", Name_Param->first_name, Name_Param->last_name, Name_Param->jedi_name);
        }

        return;
}

void * allocate(unsigned int size){
    heap_usage = heap_usage + size;
    printf("The current heap size after heap allocation is %d\n", heap_usage);
    void *heapMem = malloc(size);
    if(heapMem == NULL)
        printf("Pointer is NULL\n");
    else
        printf("Pointer is not NULL\n");

    return heapMem;
}

void * deallocate(void *heapMem, int size){
    heap_usage = heap_usage - size;
    printf("The current heap size after heap deallocation is %d\n", heap_usage);
    free(heapMem);
    heapMem = NULL;
    return NULL;
}

Answer 1

当您尝试取消引用name时，您正在调用未定义的行为，因为您没有为其分配任何空间。你在name中有一个指向无处的指针（我相信它实际上已初始化为0，因为它是静态的）。在main中，您必须执行name = malloc(sizeof *name);之类的操作，或者您可以将声明更改为struct Names name;

第二眼看，name仅在main中使用，因此请在此处声明。无需在更广泛的范围内宣布它。

int main(void)
{
  // no point in dynamically allocating memory in this case. You don't need
  // much and you know exactly how much you need (just 1 struct)
  struct Names name;
  // but if you want to dynamically allocate it..
  // struct Names* name = malloc(sizeof *name);
  ....
  // change all your "name->" to "name." if you did not malloc
  // if you did not malloc, you must pass the address of name
  // to jediName
  // jediName(&name);

  // .. do you work

  // if you used malloc above, don't forget to free your memory
  // free(name);

  return 0;
}

另见Why is “while ( !feof (file) )” always wrong?

Answer 2

非常感谢你的帮助。 代码中的主要问题是缺少名称的内存分配，'=='以及在调试代码时编写的一些其他额外代码。

以下是最终的c文件。

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

#include "Structures.h"

int main(){

    char buffer1[250];
    char buffer2[250];

    FILE * fp;

        printf("Enter the first & last name : \n");
        scanf("%s %s", buffer1, buffer2 );

    fp = fopen("names.txt", "a");
    fprintf(fp, "\n%s %s", buffer1, buffer2);
    fclose(fp);


    fp = fopen("names.txt","r");

        name = allocate(10);
        name->first_name = allocate(10);
        name->last_name = allocate(10);
        name->jedi_name = allocate(10);

    while(!feof(fp)){
        fscanf(fp, "%s %s", name->first_name, name->last_name);
        jediName(name);
    }

    deallocate(name->first_name, 10);
        deallocate(name->last_name, 10);
        deallocate(name->jedi_name, 10);
        deallocate(name, 10);

    fclose(fp);

    return 0;
}

void jediName(struct Names *Name_Param){
        if(strlen(Name_Param->first_name)<2 || strlen(Name_Param->last_name)<3)
                printf("Name of %s %s is too short to compute a jedi name\n", Name_Param->first_name, Name_Param->last_name);
        else{
                Name_Param->jedi_name[0] = Name_Param->last_name[0];
                Name_Param->jedi_name[1] = Name_Param->last_name[1];
                Name_Param->jedi_name[2] = Name_Param->last_name[2];
                Name_Param->jedi_name[3] = Name_Param->first_name[0];
                Name_Param->jedi_name[4] = Name_Param->first_name[1];
                printf("Jedi Name for %s %s is %s\n", Name_Param->first_name, Name_Param->last_name, Name_Param->jedi_name);
        }

        return;
}

void * allocate(unsigned int size){
    heap_usage = heap_usage + size;
    printf("The current heap size after heap allocation is %d\n", heap_usage);
    void *heapMem = malloc(size);
    if(heapMem == NULL)
        printf("Pointer is NULL\n");
    else
        printf("Pointer is not NULL\n");

    return heapMem;
}

void * deallocate(void *heapMem, int size){
    heap_usage = heap_usage - size;
    printf("The current heap size after heap deallocation is %d\n", heap_usage);
    free(heapMem);
    heapMem = NULL;
    return NULL;
}