Question

 stack <char> stck;
 string str;

 stck.push('0');

 str.append("test:");
 //test:
 cout << str << endl;

 str.append(&stck.top());
 //test:0═══════════════¤¤¤¤▌▌▌▌,╘╥XЕ┤
 cout << str << endl;

Why is this happening?

Answer 1

Maciej Hehl is correct about why you’re getting unwanted behavior.

To get the behavior that you want, you need to append the character itself, not a pointer to it. You are correct in saying (in your comment to Kalim’s answer) that there is no override of std::string::append that takes just a char. However, there is an override std::string::append(std::size_t, char), which appends the character (second argument) a certain number of times (first argument).

So the correct way to write what you want would be:

str.append(1, stck.top()); // Append one copy of the character at the top of the stack 

Or, alternatively, just use the overload for the += operator, which accepts a char:

str += stck.top();