Question

string str1("someString");
string str2 = string(str1);//how many copies are made here
    //copy2 = copy1?

When you assign a string with string(otherString), does it copy the value in the parentheses then copy that value to the variable?

Answer 1

In real life there will be one copy, though theoretically it depends on the version of the language your compiler implements.

string(str1) is going to create a temporary that’s a copy of str1.

In C++98/03, the compiler will theoretically use copy initialization to initialize str2 from that temporary, so in theory a second copy will be made at that point. In reality, you’ll probably have a hard time finding a compiler that doesn’t elide one of those copy operations though (at least if optimization is enabled).

In C++11, std::string has a move constructor (one that takes an rvalue reference), which should be used to initialize str2, so the second copy shouldn’t even theoretically happen.