> On Dec 17, 2018, at 11:10 AM, Chris Dumez <cdu...@apple.com> wrote:
>
>
>
>> On Dec 17, 2018, at 10:27 AM, Alex Christensen <achristen...@apple.com
>> <mailto:achristen...@apple.com>> wrote:
>>
>>>>>> On Dec 14, 2018, at 1:37 PM, Chris Dumez <cdu...@apple.com
>>>>>> <mailto:cdu...@apple.com>> wrote:
>>>>>
>>>>>>
>>>>>> As far as I know, our convention in WebKit so far for our types has been
>>>>>> that types getting moved-out are left in a valid “empty” state.
>> This is not necessarily true. When we move out of an object to pass into a
>> function parameter, for example, the state of the moved-from object depends
>> on the behavior of the callee. If the callee function uses the object, we
>> often have behavior that leaves the object in an “empty” state of some kind,
>> but we are definitely relying on fragile undefined behavior when we do so
>> because changing the callee to not use the parameter changes the state of
>> the caller. We should never assume that WTFMove or std::move leaves the
>> object in an empty state. That is always a bug that needs to be replaced by
>> std::exchange.
>
> Feel like we’re taking about different things. I am talking about move
> constructors (and assignment operators), which have a well defined behavior
> in WebKit. And it seems you are talking about WTFMove(), which despite the
> name does not “move” anything, it is merely a cast.
> In the case you’re talking about the caller does NOT call the move
> constructor, it merely does a cast so I do not think your comment invalidates
> my statement. Note that in my patch, I was nearly WTFMove()ing the data
> member and assigning it to a local variable right away, calling the move
> constructor.
Also note that may of us already rely on our move constructors’ behavior, just
search for WTFMove(m_responseCompletionHandler) in:
https://trac.webkit.org/changeset/236463/webkit
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