Re: [boost] storing intrusive_ptr in atomic?!

On Friday 25 October 2013 10:25:16 Giovanni Piero Deretta wrote:

On Fri, Oct 25, 2013 at 10:22 AM, Oliver Kowalke

wrote:

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2013/10/25 Giovanni Piero Deretta

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Intrusive_ptr doesn't have tivial copy constructor (how could it have? it needs to update the counter), ergo is not trivially copyable and the

above

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two point do not apply.

but the standard says 'trivially copyable' not 'trivial copy constructor' - e.g. the code examples by the standard document gives correct results for intrusive_ptr (because all criteria are fulfilled). does this mean the standard document contains a false wording/examples?

I do not have the standard at hand, but a trivially copyable class is a class that: 1. Has no non-trivial copy constructors (this also requires no virtual functions or virtual bases)

2. Has no non-trivial move constructors

3. Has no non-trivial copy assignment operators

4. Has no non-trivial move assignment operators

5. Has a trivial destructor

[from cppreference.com, which may or may not be authoritative]

You are correct, I'll just provide some references: Trivially copyable types are defined in 3.9/9 [basic.types]. [...] Scalar types, trivially copyable class types (Clause 9), arrays of such types, and cv-qualified versions of these types (3.9.3) are collectively called trivially copyable types. [...] Trivially copyable class types are defined in 9/6 [class]. A trivially copyable class is a class that: — has no non-trivial copy constructors (12.8), — has no non-trivial move constructors (12.8), — has no non-trivial copy assignment operators (13.5.3, 12.8), — has no non-trivial move assignment operators (13.5.3, 12.8), and — has a trivial destructor (12.4). A trivial class is a class that has a trivial default constructor (12.1) and is trivially copyable. [ Note: In particular, a trivially copyable or trivial class does not have virtual functions or virtual base classes. — end note ]