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From David Kimura <dkim...@pivotal.io>
Subject Re: Return types form methods on Cache
Date Tue, 19 Sep 2017 17:54:40 GMT
Oh, man. I hope I didn't just kill the original idea.  Unless we are
somehow using shared_from_this, it shouldn't be a divergence from existing
behavior?

Thanks,
David

On Tue, Sep 19, 2017 at 10:47 AM, Jacob Barrett <jbarrett@pivotal.io> wrote:

> Region returned by this would no longer be valid. It’s “references” to
> interns cache/region would be invalid. The behavior is undefined.
>
> > On Sep 19, 2017, at 10:24 AM, David Kimura <dkimura@pivotal.io> wrote:
> >
> > Err... I missed a return in example above.
> >
> > Region r = [](){ return CacheFactory::create().getRegion("myregion"); }
> ();
> >
> >> On Tue, Sep 19, 2017 at 10:19 AM, David Kimura <dkimura@pivotal.io>
> wrote:
> >>
> >> I favor values, but we should probably be diligent.
> >>
> >> Do any of the objects returned from Cache depend on Cache to out-live
> the
> >> returned object?  A quick scan suggested no, but we still have a
> >> std::enable_shared_from_this<Cache>.  Maybe dead code.  In code
> example,
> >> if this happens (for any cache.get*), could we be in trouble or is this
> >> user error?
> >>
> >> Region r = [](){ CacheFactory::create().getRegion("myregion"); }();
> >> // Cache is out of scope.
> >> // What is expected behavior?
> >> r.put("key", "value");
> >>
> >> Thanks,
> >> David
> >>
> >> On Mon, Sep 18, 2017 at 7:44 PM, Jacob Barrett <jbarrett@pivotal.io>
> >> wrote:
> >>
> >>>
> >>>
> >>>> On Sep 18, 2017, at 7:34 PM, Kirk Lund <klund@apache.org> wrote:
> >>>>
> >>>> I would vote +1 for a more attractive, professional and user-friendly
> >>> API.
> >>>> I'm not sure if there's a perf or memory-usage reason for using
> >>>> "std::shared_ptr<?>" to types instead of returning values, but
the end
> >>>> result does not look like a professional API to me.
> >>>
> >>> There really isn’t, especially if you look at what we did dirty
> >>> CacheFactory::getCache by returning a value that can be moved into the
> heap
> >>> and a shared point of one wants but not being forced into it. RVO
> tricks
> >>> can event make that move a noop.
> >>>
> >>> auto r = cache.getRegion(...);
> >>> Where decltype(r) == Region
> >>> and
> >>> auto rp = std::make_shared<Region>(cache->getRegion());
> >>> Where decltype(rp) == shared_ptr<Region>
> >>>
> >>> Would both be valid.
> >>>
> >>>
> >>>
> >>
>

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