Calling constructors in c++ without new

Question

I\'ve often seen that people create objects in C++ using

Thing myThing(\"asdf\");

Instead of this:

Thing myThing = Thing(\"         


        

Answer 1

In append to JaredPar answer

1-usual ctor, 2nd-function-like-ctor with temporary object.

Compile this source somewhere here http://melpon.org/wandbox/ with different compilers

// turn off rvo for clang, gcc with '-fno-elide-constructors'

#include 
class Thing {
public:
    Thing(const char*){puts(__FUNCTION__ );}
    Thing(const Thing&){puts(__FUNCTION__ );}   
    ~Thing(){puts(__FUNCTION__);}
};
int main(int /*argc*/, const char** /*argv*/) {
    Thing myThing = Thing("asdf");
}

And you will see the result.

From ISO/IEC 14882 2003-10-15

8.5, part 12

Your 1st,2nd construction are called direct-initialization

12.1, part 13

A functional notation type conversion (5.2.3) can be used to create new objects of its type. [Note: The syntax looks like an explicit call of the constructor. ] ... An object created in this way is unnamed. [Note: 12.2 describes the lifetime of temporary objects. ] [Note: explicit constructor calls do not yield lvalues, see 3.10. ]

---

Where to read about RVO:

12 Special member functions / 12.8 Copying class objects/ Part 15

When certain criteria are met, an implementation is allowed to omit the copy construction of a class object, even if the copy constructor and/or destructor for the object have side effects.

Turn off it with compiler flag from comment to view such copy-behavior)