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https://issues.apache.org/jira/browse/MESOS-1008?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Benjamin Mahler updated MESOS-1008:
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Summary: Reduce copying in stout / libprocess primitives {Try, Option,
Result, Future}. (was: Reduce copying in stout primitives {Try, Option,
Result}.)
> Reduce copying in stout / libprocess primitives {Try, Option, Result, Future}.
> ------------------------------------------------------------------------------
>
> Key: MESOS-1008
> URL: https://issues.apache.org/jira/browse/MESOS-1008
> Project: Mesos
> Issue Type: Improvement
> Reporter: Benjamin Mahler
> Assignee: Benjamin Mahler
>
> The following will discuss Try, but the same applies to Option and Result.
> Currently retrieving the value from a Try requires a copy:
> T get() const { ... return *t; }
> Instead, we can return a const&:
> const T& get() const { ... return *t; }
> For existing callers, this should be fairly seamless:
> const T& t = try.get(); // No change needed.
> T t = try.get(); // No change needed, T is already required to be copyable.
> try.get().mutator(); // Will no longer compile, but we should not allow
> this anyway!
> const T& t = try.get();
> try = T(); // t is now garbage!
> t.foo(); // No longer works.
> The last case is the most concerning as this mistake cannot be caught at
> compile-time. We could remove the assignment operators, but this seems overly
> restrictive. We could also guard (via CHECK) the assignment operator after a
> get() operation, but of course, we're also preventing valid Try usage if we
> go this route. The best path may simply be to leave the assignment operators
> as is (many callers already make copies).
> We can also add C++11 support for move to pilfer the Try, to avoid copies in
> the caller entirely:
> T&& move() const { ... } // After a move(), we must guard Try operations.
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