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

[David Blaikie]

On Jul 17, 2014 8:20 PM, "Zachary Turner" <zturner at google.com> wrote:
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> On Thu, Jul 17, 2014 at 4:58 PM, David Blaikie <dblaikie at gmail.com> wrote:
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>> On Thu, Jul 17, 2014 at 4:45 PM, Alp Toker <alp at nuanti.com> wrote:
>> > In many cases there shouldn't be a need for smart pointers at all,
because
>> > the object is owned by a central facility's smart pointer so it's safe
to
>> > just pass around the pointer in ephemeral contexts like stack-based
>> > instances. In such context raw pointers and references aren't scary --
>> > they're just fine.
>>
>> There's no contention there - if the pointer is non-owning, there's no
>> smart pointer to use. Indeed using a smart pointer for a non-owning
>> pointer would actually break the code by causing double deletes, etc.
>>
>> Well, shared_ptr notwithstanding - but, yes, choosing between
>> unique_ptr + non-owning pointers and shared_ptr can sometimes be
>> non-obvious, but I'm hopeful we generally agree that if there is a
>> dominating owner they can be given exclusive ownership through a
>> unique_ptr and everyone else can use raw pointers.
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> What about weak_ptr?

I'd generally reserve them for use when the auto-null behavior is
necessary, for example in lazy caches. Though it seems the situations that
call for them are relatively rare - its a good tool when you need it.

I suppose in some cases it might be nice to have something like AssertingVH
that's a raw pointer in release builds and an asserting weak_ptr-like thing
in debug builds.
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