>583
変換元の値が、変換先の整数型の上限を超えている場合は、そもそも実装依存だよ。
static_cast 使おうが reinterpret_cast 使おうが。

> 4.7 Integral conversions
> 3 If the destination type is signed, the value is unchanged if it can be represented in
> the destination type (and bitfield width); otherwise, the value is implementationdefined.