[
https://issues.apache.org/jira/browse/KUDU-2028?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16033996#comment-16033996
]
Todd Lipcon commented on KUDU-2028:
-----------------------------------
https://stackoverflow.com/questions/8640393/move-capture-in-lambda might be
relevant? But yea, I think we tend to use raw pointers or shared_ptrs
> Async Proxy callbacks cannot capture non-copyable types
> -------------------------------------------------------
>
> Key: KUDU-2028
> URL: https://issues.apache.org/jira/browse/KUDU-2028
> Project: Kudu
> Issue Type: Improvement
> Reporter: Henry Robinson
> Assignee: Henry Robinson
> Priority: Minor
>
> Callbacks that are passed to {{Proxy::AsyncRequest()}} are passed by
> reference. They are then passed by value into {{OutboundCall()}}, where that
> copy is saved.
> This means that you can't have a callback that captures a non-copyable type:
> {code}
> unique_ptr<Foo> my_foo = make_unique<Foo>();
> auto cb = [f(move(my_foo))]() {
> };
> proxy->AsyncRequest("method", req, response, controller, cb); // <-- error,
> missing copy c'tor for unique_ptr<Foo>
> {code}
> This is a sometimes useful idiom for passing ownership of something into the
> callback, where it can get destroyed some time in the future, after the
> caller has ceased to exist.
> A solution would be for {{AsyncRequest()}} (and its generated wrappers) to
> take a {{ResponseCallback}} by value, and to {{move()}} it until it was
> copied. This kind of transformation has its drawbacks (if for some reason the
> parameter doesn't get copied, it is more expensive than pass-by-reference),
> but seems a reasonable tradeoff here.
--
This message was sent by Atlassian JIRA
(v6.3.15#6346)
