A function returns to its caller by the return statement.
The expr-or-braced-init-list of a return statement is called its operand. A return statement with no operand shall be used only in a function whose return type is cv void, a constructor ([class.ctor]), or a destructor ([class.dtor]). A return statement with an operand of type void shall be used only in a function whose return type is cv void. A return statement with any other operand shall be used only in a function whose return type is not cv void; the return statement initializes the glvalue result or prvalue result object of the (explicit or implicit) function call by copy-initialization ([dcl.init]) from the operand. [ Note: A return statement can involve an invocation of a constructor to perform a copy or move of the operand if it is not a prvalue or if its type differs from the return type of the function. A copy operation associated with a return statement may be elided or converted to a move operation if an automatic storage duration variable is returned ([class.copy]). — end note ] [ Example:
std::pair<std::string,int> f(const char* p, int x) {
return {p,x};
}
— end example ] Flowing off the end of a constructor, a destructor, or a function with a cv void return type is equivalent to a return with no operand. Otherwise, flowing off the end of a function other than main ([basic.start.main]) results in undefined behavior.
The copy-initialization of the result of the call is sequenced before the destruction of temporaries at the end of the full-expression established by the operand of the return statement, which, in turn, is sequenced before the destruction of local variables ([stmt.jump]) of the block enclosing the return statement.