Comment by masklinn

19 hours ago

The only thing that is statically known here is that you’re wrong. The function I posted only moves its parameter half the time, at random. You may want to treat it as moved-from either way, but factually that’s just not what is happening.

5 comments

masklinn

charcircuit 19 hours ago

This is like trying to defend that you can't statically know the result of 1 + 2 because:

  void foo() {
    std::random_device rdev {};
    auto dist = std::uniform_int_distribution<>(0, 1);
    if (dist(rdev)) {
      int res = 1 + 2;
    }
  }

I can tell you for sure that the result of 1 + 2 will be 3.

masklinn 18 hours ago
> This is like trying to defend that you can't statically know the result of 1 + 2
It is completely unlike that. tsimionescu is asserting that they can always know statically whether `foo` will move its parameter. The function I provided is a counter-example to that assertion.
Of course the branch body always moves, that's what it's there for. That has no bearing on the argument.
- charcircuit 11 hours ago
  
  >Of course the branch body always moves
  >That has no bearing on the argument.
  That is the whole argument. Let me quote the other person: "My claim is that, if I call `foo(std::move(myObj))`, it is statically knowable if `foo` receives a copy of `myObj` or whether it is moved to it."
  It is saying that for "auto pp = std::move(p);" we will know if it uses the move assign constructor or the copy assign constructor.
  
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