Question

我正在尝试将一个char变量转换为const char变量，但是出现以下错误。 char的内容可以，在这种情况下为“ H”和“ e”，但是当我转换为const char *时，后面会有字母+其他东西。你们能告诉我我在哪里做错了吗？

请通过链接查看图片！

#include <iostream>
#include <Windows.h>
#include <lmcons.h>
#include <stdio.h>
#include <stdlib.h>

    char Body[] = { 'H', 'e', 'l', 'l', 'o' };       // elements of char array


    int size = sizeof(Body);                          // get size of Body array
    char Line;

    std::cout << "Size : " << size << "\n";           // view the size of Body array

    for(int i=0; i<=size; i++)                        // for statement : from first element to the last element of array
    {                                                 // beginning  of for statement

    Line = Body[i];                                   // get each element from Body array and put to char variable

    std::cout << "Char : " << Line << "\n";           // view the content of char variable


    const char *Line2 = &Line ;                       // convert from from char to const char*


    std::cout << "Const char : " << Line2 << "\n";     // view the content of const char* variable

    }                                                  // end of for statement

enter image description here

Answer 1

const char *Line2 = &Line ;

不会从角色中神奇地创建一个字符串；因为字符串必须以Null（或0）结尾，所以您不能将此指针传递给cout，因为它希望处理多个字符。如果您将其更改为

char Line[2] = {0};  // 0 initialise all the chars
Line[0] = Body[i];
Line[1] = 0;         // completely not required, but just making the point

char* Line2 = &Line[0];   // there are other cleaner ways, but this shows explicitly what is happening
std::cout << Line2;

您没有UB。

Answer 2

问题是，当您以如下方式运行循环时，您正在访问Body [5]

for(int t=0;t<=sizeof(Body);t++){}

如果您删除那个=号，那没关系。

for(int t=0;t<sizeof(Body);t++){}

还尝试转换

std::const char *Line2 = const_cast<const char *>(&Line );

使用std::const_cast<>()将非常量转换为常量数据类型。

如果要直接从控制台删除那些多余的东西，还需要取消引用const char *。 std :: cout尝试打印所有内容，直到遇到null为止（如果您将其传递给const char *

所以

std::cout << "Const char : " << *Line2;

Answer 3

问题是您没有用空字符（Body）终止\0。第二个问题是您试图访问超出范围的循环。代码应如下所示：

char Body[] = { 'H', 'e', 'l', 'l', 'o', '\0' };       // elements of char array

int size = sizeof(Body);                          // get size of Body array
char Line;

std::cout << "Size : " << size << "\n";           // view the size of Body array

for(int i=0; i<size; i++)                        // for statement : from first element to the last element of array
{                                                 // beginning  of for statement

Line = Body[i];                                   // get each element from Body array and put to char variable

std::cout << "Char : " << Line << "\n";           // view the content of char variable


const char *Line2 = &Line ;                       // convert from from char to const char*


std::cout << "Const char : " << Line2 << "\n";     // view the content of const char* variable

}                                                  // end of for statement

在c / c ++语言中，任何原始字符串的末尾都需要null char，因为这有助于它理解字符串的结尾。

将const char *转换为char时出错

3 个答案: