在将char *赋给字符串变量后删除它 [英] Deleting char* after assigning it to a string variable

问题描述

我执行了下面的代码，它的工作完美。因为它是关于指针，我只是想确定。虽然我确信将字符串赋值给字符串会产生一个副本，即使我删除了char *，字符串变量也会保留该值。

I have executed the below code and it works perfectly. Since it is about pointers, I just want to be sure. Though I'm sure that assigning char* to string makes a copy and even if I delete char*, string var is gonna keep the value.

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

    int main()
    {
        std::string testStr = "whats up ...";
        int strlen = testStr.length();
        char* newCharP = new char[strlen+1];
        memset(newCharP,'\0',strlen+1);
        memcpy(newCharP,testStr.c_str(),strlen);


        std::cout << "  :11111111   :   " << newCharP << "\n";
        std::string newStr = newCharP ;

        std::cout << "  2222222 : " << newStr << "\n";
        delete[] newCharP;
        newCharP = NULL;

        std::cout << "  3333333 : " << newStr << "\n";
    }

我只是更改公司项目中的一些代码，char *在C ++中的函数之间。 char *指针已复制到字符串，但char *在函数结束时被删除。我找不到任何具体的原因。所以我只是删除的char *，一旦它被复制到字符串。这会使任何问题...？

I'm just changing some code in my company project and char* are passed between functions in C++. The char* pointer has been copied to the string, but the char* is deleted in the end of the function. I couldn't find any specific reason for this. So I'm just deleting the char*, as soon as it is copied into a string. Would this make any problem ...?

P.S：我已经在Codereview中提出了这个问题，但我建议将其移动到SO。

P.S : I have already asked this question in Codereview , but I got suggestion to move it to SO. So i have flagged it for close there and posting the question here.

推荐答案

没有问题，只要 newChar 指向一个以null结束的字符串，并且不是null本身。

There is no problem, as long as newChar points to a null-terminated string, and is not null itself.

std :: string 有一个构造函数允许从 const char * 。它创建一个由输入 const char * 表示的字符串的副本，因此它在假设 char * 是一个空结束的字符串，因为没有其他方法知道有多少字符要复制到字符串自己的数据存储。此外， NULL 指针实际上被标准禁止。

std::string has constructor that allows an implicit construction from a const char*. It makes a copy of the character string represented by the input const char * so it works under the assumption that the char* is a null terminated string, since there is no other way to know how many characters to copy into the string's own data storage. Furthermore, a NULL pointer is actually disallowed by the standard.

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