字符串输入未在屏幕上正确打印

Question

我正在尝试从用户输入中读取一个字符串，然后将其打印在屏幕上。但是，当字符串打印在控制台上时，它有点乱码。有趣的是，它在 Visual Studio 而不是 CodeBlocks 中有效。

#include <iostream>
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>

int main() {
    int i, num_bytes;
    char sentence[] = "";
    std::cout << "Please enter your name: ";
    //fgets(sentence, 100, stdin);
    //scanf("%[^\n]%*c", sentence);
    //scanf("%[^\n]", sentence);
    std::cin >> sentence;
    num_bytes = strlen(sentence);

    LPVOID ptr = VirtualAlloc(NULL, num_bytes, MEM_RESERVE, PAGE_READWRITE);
    ptr = VirtualAlloc(ptr, num_bytes, MEM_COMMIT, PAGE_READWRITE);

    if (ptr) {
        char* char_ptr = static_cast<char*>(ptr);

        for (i = 0; i < num_bytes; i++) {
            char_ptr[i] = sentence[i];
        }

        std::cout << "Allocated Memory Address: " << (void *)ptr << std::endl;

        std::cout << "Press Enter to print out the characters.\n";
        getchar();

        for (i = 0; i < num_bytes; i++) {
            std::cout << char_ptr[i];
        }

        std::cout << "\nPress Enter to clear memory." << std::endl;
        getchar();

        VirtualFree(ptr, 0, MEM_RELEASE);
    } else {
        std::cout << "Could not allocate " << num_bytes << " of memory." << std::endl;
    }

    std::cout << "\nPress Enter to continue." << std::endl;
    getchar();
}

Answer 1

您应该明确指定字符串的内存大小。该代码：

char sentence[] = "";

声明句子的最大长度为 0（+1 个零符号）。当然，您将更多数据写入非您的内存中。试试这个：

char sentence[200] = "";

Answer 2

而不是这个：

    char sentence[] = "";
    std::cout << "Please enter your name: ";
    //fgets(sentence, 100, stdin);
    //scanf("%[^\n]%*c", sentence);
    //scanf("%[^\n]", sentence);
    std::cin >> sentence;
    num_bytes = strlen(sentence);

你最好这样写：

    constexpr std::streamsize BUFFER_SIZE { 100 };
    std::array<char, BUFFER_SIZE> sentence { }; // use the more modern std::array

    std::cout << "Please enter your name: ";
    std::cin.getline( sentence.data( ), BUFFER_SIZE ); // will only read 100 chars
                                                       // including spaces and tabs

    num_bytes = strlen(sentence.data( ));

其余与您的代码相同。但是现在用户也可以输入 space 个字符，并且它们不会导致缓冲区溢出，因为 std::cin.getline 只会从标准输入流中读取有限数量的字符。

字符串输入未在屏幕上正确打印

string input not printed correctly on the screen

c++

memory

string

winapi

virtualalloc