Should I compare a std::string to “string” or “string”s?

Question

Consider this code snippet:

bool foo(const std::string& s) {
    return s == \"hello\"; // comparing against a const char* literal
}

bool bar(const std::str         


        

Answer 1

From my understanding, this means that we will need to construct a std::string anyway in order to perform the comparison, so I suspect the overhead will be the same in the end (although hidden by the call to operator==).

This is where that reasoning goes wrong. std::compare does not need to allocate its operand as a C-style null-terminated string to function. According to one of the overloads:

int compare( const CharT* s ) const; // (4)

4) Compares this string to the null-terminated character sequence beginning at the character pointed to by s with length Traits::length(s).

Although whether to allocate or not is an implementation detail, it does not seem reasonable that a sequence comparison would do so.