9 Statements [stmt.stmt]

9.6 Jump statements [stmt.jump]

9.6.3 The return statement [stmt.return]

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, or a destructor.
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 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 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.