Tutorial by Examples

There are places in the standard where an object is copied or moved in order to initialize an object. Copy elision (sometimes called return value optimization) is an optimization whereby, under certain specific circumstances, a compiler is permitted to avoid the copy or move even though the standard...

C++17 Normally, elision is an optimization. While virtually every compiler support copy elision in the simplest of cases, having elision still places a particular burden on users. Namely, the type who's copy/move is being elided must still have the copy/move operation that was elided. For example:...

If you return a prvalue expression from a function, and the prvalue expression has the same type as the function's return type, then the copy from the prvalue temporary can be elided: std::string func() { return std::string("foo"); } Pretty much all compilers will elide the tempor...

When you pass an argument to a function, and the argument is a prvalue expression of the function's parameter type, and this type is not a reference, then the prvalue's construction can be elided. void func(std::string str) { ... } func(std::string("foo")); This says to create a tem...

If you return an lvalue expression from a function, and this lvalue: represents an automatic variable local to that function, which will be destroyed after the return the automatic variable is not a function parameter and the type of the variable is the same type as the function's return type ...

If you use a prvalue expression to copy initialize a variable, and that variable has the same type as the prvalue expression, then the copying can be elided. std::string str = std::string("foo"); Copy initialization effectively transforms this into std::string str("foo"); (th...