Operators "new" and "delete" in C++

Question

I ran into a problem, from an exercise in Bjarne Stroustrup's book Programming: Principles and Practice Using C++ (2nd edition), at the very end of chapter 17 for the Exercises section, exercise 7:

The program works normally if you do not use delete linearray1;. Accordingly, the problem is when deleting the allocated dynamic memory.

I have no error messages or warnings in the console. However, VS Code shows me that problem in this line (delete linearray1). Highlights the entire line in yellow.

Tell me how to solve the problem in this case. How can I correctly clear the allocated memory?

#include <iostream> 

void fillarray(std::string& array)
{ 
    char* linearray1 {new char};
    char* line = linearray1;
    std::cin >> line;
    
    while (*line)
    {   
        if (*line == '!')
            break;
        array += *line;
        line++;
    }
    delete linearray1;
}

int main()
{

    std::string linearray1;
    fillarray(linearray1);
    std::cout << "\n" << linearray1;
    return 0;
}

Answer 1

To summarize the comments...

In fillarray(), you are allocating dynamic memory for only 1 char, and then passing that buffer to the operator>> overload that reads a word into a char[] buffer. That overload will try to read and output more than 1 char (including a '\0' terminator) until it encounters a whitespace character that ends the input. So, you end up invoking undefined behavior by writing out of bounds of your dynamic memory, thus corrupting surrounding memory. And in this case, delete seems to be just an unwitting victim of that behavior.

If you really want to read the input 1 char at a time, then use the operator>> overload that reads a single char, or use the istream::get(char&) method instead, eg:

void fillarray(std::string& array)
{ 
    char* pch {new char};
    
    while ((std::cin >> *pch) && (*pch != '!'))
    // or: while (std::cin.get(*pch) && (*pch != '!'))
    {   
        array += *pch;
    }

    delete pch;
}

But, there is no need to dynamically allocate 1 char by itself, just use a local char variable instead, eg:

void fillarray(std::string& array)
{ 
    char ch;
    
    while ((std::cin >> ch) && (ch != '!'))
    // or: while (std::cin.get(ch) && (ch != '!'))
    {   
        array += ch;
    }
}

However, in this particular example, you can just read directly into your target std::string by using std::getline() instead, eg:

void fillarray(std::string& array)
{ 
    std::getline(std::cin, array, '!');
}