Re: [boost] [smart_ptr][thread][test] breaking change on shared_ptr operator bool.

Subject: Re: [boost] [smart_ptr][thread][test] breaking change on shared_ptr operator bool.
From: Vicente Botet (vicente.botet_at_[hidden])
Date: 2012-12-12 05:45:14

Olaf van der Spek-3 wrote
> On Mon, Dec 10, 2012 at 5:23 PM, Peter Dimov <

> lists@

> > wrote:
>> Olaf van der Spek wrote:
>>>
>>> On Mon, Dec 10, 2012 at 4:27 PM, Peter Dimov <

> lists@

> > wrote:
>>> > Olaf van der Spek wrote:
>>> >
>>> >> What's the rationale for this breaking change?
>>> >
>>> > Compatibility with C++11?
>>>
>>> The 'old' boost::shared_ptr seemed to work fine on C++11.
>>
>>
>> Sure. It seems that you're being deliberately obtuse for rhetorical
>> reasons,
>> but all right.
>>
>> In C++11, the idiomatic way to make a class convertible to bool is via an
>> explicit operator bool. The language has been specifically changed to
>> support this use case. The standard library has been changed to use this
>> idiom for each of its convertible to bool types, including
>> std::shared_ptr.
>> For better or worse, this will be how convertible to bool C++11 types
>> will
>> behave.
> 
> I know. And boost::shared_ptr behaving the same as std::shared_ptr is
> nice, I'm just wondering whether that's more important than
> maintaining compatibility with older Boost releases.
> What real problem with keeping the old behavor have?

Imagine you need to use boost::shared_ptr in a part of your application and
std::shared_ptr in another part. It would be surprising if the behavior for
the same operation is not the same, isn't it?

I think Boost libraries implementing c++11 libraries should be as close as
possible as the standard. This doesn't mean that the author can not make
some deviations.

Respect to compatibility, it is always better to have a deprecation period,
but the required change in this case is so minor that documenting the break
and how to take care of it should be enough.
 
Best,
Vicente

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