memcpy错误:分段错误(核心已转储) [英] memcpy error : Segmentation fault (core dumped)

问题描述

我正在尝试使用memcpy将C中的一个字符串复制到另一个字符串中，并使用以下代码:

I'm trying to copy one string to another in c using memcpy with the following code:

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


typedef struct fullName
{
    char* firstName;
    char* lastName;
} NAME;

int main()
{              
    NAME myName, hisName;

    myName.firstName =  "aaaaaaa";
    hisName.firstName = "bbbbbb";

    memcpy(myName.firstName, hisName.firstName, sizeof(hisName.firstName));

    printf("myName.firstName = %s\n", myName.firstName);
    printf("hisName.firstName = %s\n", hisName.firstName);
}

，运行程序后出现分段错误(核心已转储)错误 我试图将firstName和lastName声明为chars数组的指针，而不是char的指针，但是错误仍然存​​在.我想念什么?请帮助...

and it gives Segmentation fault (core dumped) Error after running the program I tried to declare firstName and lastName as pointer to an array of chars rather than pointer to char but the error persists . what am I missing ?! plz help...

仅供参考..我正在使用Ubuntu 14，正在使用gcc(Ubuntu 4.8.2-19ubuntu1)...

FYI .. I'm working on Ubuntu 14 and I'm using gcc (Ubuntu 4.8.2-19ubuntu1)...

推荐答案

您正在为myName.firstName和hisName.firstName分配指向字符串文字的指针.字符串文字无法修改，这就是导致您出错的原因.

You are assigning myName.firstName and hisName.firstName with pointers to string literals. String literals cannot be modified, which is what's causing your error.

要实现所需的功能，可以将firstName声明为char数组，也可以为其分配内存(作为char指针).

To achieve what you want, you can either declare firstName as a char array, or allocate memory to it (as a char pointer).

数组方法:

typedef struct fullName
{
        char firstName[256]; // a sufficiently large number
        char lastName[256];
} NAME;

int main()
{              
        NAME myName, hisName;
        strcpy(myName.firstName, "aaaaaaa"); // You can't assign a string directly
        strcpy(hisName.firstName, "bbbbbb");
        memcpy(myName.firstName, hisName.firstName, sizeof(hisName.firstName));
        printf("myName.firstName = %s\n", myName.firstName);
        printf("hisName.firstName = %s\n", hisName.firstName);

}

分配方法:

typedef struct fullName
{
        char* firstName;
        char* lastName;
} NAME;

int main()
{              
        NAME myName, hisName;
        size_t buffersize = 256; // a sufficiently large number
        myName.firstName = malloc(buffersize);
        hisName.firstName = malloc(buffersize); // same for lastName

        strcpy(myName.firstName, "aaaaaaa");
        strcpy(hisName.firstName, "bbbbbb");
        memcpy(myName.firstName, hisName.firstName, buffersize); // You can't use sizeof() as this will give the size of a pointer
        printf("myName.firstName = %s\n", myName.firstName);
        printf("hisName.firstName = %s\n", hisName.firstName);

}

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