220 8337 <52C488CB.3030805@gmail.com> article
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From: Matthew Woehlke <mwoehlke.floss@gmail.com>
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Subject: Re: Proposal: Default swap operation
Date: Wed, 01 Jan 2014 16:29:47 -0500
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On 2014-01-01 14:53, Ville Voutilainen wrote:
> On 1 January 2014 21:24, Thiago Macieira <thiago@macieira.org> wrote:
>> On quarta-feira, 1 de janeiro de 2014 12:56:21, Matthew Woehlke wrote:
>>>> Huh? I'm pretty sure this is already allowed.
>>>
>>> Hmm... gcc at least seems to allow it :-D. I guess I assumed it wasn't,
>>> as I cant recall that any of the 'what's new in C++11' I've read
>>> mentioned it...
>>
>> It is, but note that it doesn't emit a symbol for other translation units to
>> see. The program is ill-defined if any translation unit trying to destroy Foo
>> doesn't see the = default.
>
>
> I don't see any wording in the standard that would require other TUs to
> see the =default to use the function.

I'm inclined to agree. I didn't consult the spec, but when I tried using 
it in a project, I am not seeing link errors that I would expect if the 
definition wasn't available to other TU's. (And I *do* see link errors 
if I omit the dtor definition entirely, so the dtor is definitely being 
referenced.)

I'd also be curious about your reading of the spec. It may be that 
technically such a program is ill-formed, but existing compilers (or at 
least gcc) "DTRT" (i.e. behave in the desired manner) anyway?

-- 
Matthew

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