lingbin commented on a change in pull request #2969: Fixed the move-assigment
of `Status`
URL: https://github.com/apache/incubator-doris/pull/2969#discussion_r382889942
##########
File path: be/src/common/status.h
##########
@@ -17,114 +17,136 @@ namespace doris {
class Status {
public:
- Status(): _state(nullptr) {}
+ Status() : _state(nullptr) { }
~Status() noexcept { delete[] _state; }
- // copy c'tor makes copy of error detail so Status can be returned by value
- Status(const Status& s)
- : _state(s._state == nullptr ? nullptr : copy_state(s._state)) {
- }
+ // Here _state == nullptr(Status::OK) is the most common case, so use this
as
+ // a fast path. This check can avoid one function call in most cases,
because
+ // _copy_state() is not an inline function.
+ Status(const Status& s) : _state(s._state == nullptr ? nullptr :
_copy_state(s._state)) { }
// same as copy c'tor
Status& operator=(const Status& s) {
// The following condition catches both aliasing (when this == &s),
// and the common case where both s and *this are OK.
if (_state != s._state) {
delete[] _state;
- _state = (s._state == nullptr) ? nullptr : copy_state(s._state);
+ _state = (s._state == nullptr) ? nullptr : _copy_state(s._state);
}
return *this;
}
- // move c'tor
Status(Status&& s) noexcept : _state(s._state) {
s._state = nullptr;
}
- // move assign
Status& operator=(Status&& s) noexcept {
- std::swap(_state, s._state);
+ if (_state != s._state) {
Review comment:
There are no requirements and also no prohibitions in the standard.
But for `dest = std::move(src)`, the following point is determined:
The `move-assignment` of `move-constructor` should have the **same
behavior**. Unfortunately, In Doris current implementation, the behavior of the
two methods is inconsistent.
And for `Status`, it only has one member, `_state`, which is **pointer
type**.
when the `src::_state` was moved to `dest`, it must be cleared in `src`,
otherwise, **the pointer will be referenced by both the `src` and `dest`, which
will be wrong.**
----------------------------------------------------------------
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
For queries about this service, please contact Infrastructure at:
us...@infra.apache.org
With regards,
Apache Git Services
---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscr...@doris.apache.org
For additional commands, e-mail: commits-h...@doris.apache.org
