[cfe-dev] Use of Smart Pointers in LLVM Projects

[Lang Hames]

No objections here. I'd be glad to see this go in. :)

- Lang.


On Fri, Jul 18, 2014 at 4:30 PM, Eric Christopher <echristo at gmail.com>
wrote:

> Sounds like we've got sufficient amount of momentum here for Dave to
> go ahead and recommit. Any last objections?
>
> -eric
>
> On Fri, Jul 18, 2014 at 1:35 PM, Eli Bendersky <eliben at google.com> wrote:
> >
> >
> >
> > On Fri, Jul 18, 2014 at 12:06 PM, Jordan Rose <jordan_rose at apple.com>
> wrote:
> >>
> >> I don't have much to add here besides +1. I think using std::unique_ptr
> >> even for create* functions/methods is the right way to go.
> >
> >
> > +1 smart pointers here are a win in terms of safety and
> self-documentation.
> > I don't see why create* factories should be treated differently.
> >
> > Eli
> >
> >
> >
> >>
> >> Reid's point about an abstraction penalty is interesting, but I don't
> >> think we do ownership transfers often enough to actually see a
> performance
> >> hit. (Of course, in the non-transferring case we'd just pass the
> pointer,
> >> not a 'const std::unique_ptr &' or anything.)
> >>
> >> Jordan
> >>
> >>
> >> On Jul 17, 2014, at 16:21 , David Blaikie <dblaikie at gmail.com> wrote:
> >>
> >> > There seems to be some uncertainty about the use of smart pointers
> >> > (previously OwningPtr, now std::unique_ptr and std::shared_ptr
> >> > predominantly) in the LLVM project as a whole, so here's a thread to
> >> > discuss/clarify/etc the project preferences/direction with regard to
> >> > smart pointer usage.
> >> >
> >> > For some context, see discussions in LLVM r212403 and Clang r213307.
> >> >
> >> > The basic question here seems to be whether smart pointer ownership is
> >> > a direction we want to take the LLVM project in general.
> >> >
> >> > I've seen others contribute and have myself contributed many patches
> >> > moving towards smart pointer ownership (both in the pre-C++11 days of
> >> > OwningPtr, and much moreso in the post-C++11 world with
> >> > std::unique_ptr and std::shared_ptr being usable inside containers, as
> >> > return values, etc, allowing many more opportunities).
> >> >
> >> > std::unique_ptr's been used in LLD as far back as r153620.
> >> > std::unique_ptr appeared in LLVM shortly after the C++11 switch with
> >> > Ahmed's work to migrate the project from OwningPtr to std::unique_ptr
> >> > (starting with r202609 and ending with r211259). Originally OwningPtr
> >> > was added in r45261.
> >> > Something in the order of 60 changes across clang and LLVM mention
> >> > unique_ptr in their subject and migrate various APIs to use unique_ptr
> >> > for ownership. Many of which remove uses of explicit delete or helpers
> >> > like DeleteContainerPointers (and removing explicit dtors in many of
> >> > those cases).
> >> >
> >> > Are people OK with/prefer the use of owning smart pointers in APIs?
> >> > Are there places where you've found them to be too noisy/burdensome
> >> > and would rather use raw pointers or some other abstraction? Would you
> >> > prefer pre-commit review of such changes to adequately consider
> >> > alternatives (such as?)?
> >> >
> >> > Thanks,
> >> > - David
> >> > _______________________________________________
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> >>
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> >
> >
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