• BatmanAoD@programming.dev
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    11 months ago

    The parts that seem likely to cause this confusion (which I shared when I first started using C++11) are:

    • Moves in C++ are always a potentially-destructive operation on a reference, not just a memcopy.
    • Consequently, “moving” a temporary still requires having two separate instances of the type, despite that generally not being what you want, hence RVO.
    • …but move-semantics are generally presented and understood as an “optimization”, and conceptually “take the guts of this value and re-use them as a new value” is both what RVO is doing and what move-semantics are doing.
    • std::move isn’t a compiler intrinsic and doesn’t force a move operation; it’s just a function that returns an r-value reference. So it makes it harder, not easier, for the compiler to “see through” and optimize away, even in the case where “as if” rule should make that legal.