[cfe-dev] Lambdas and the ABI?

[Hal Finkel via cfe-dev]

On 03/21/2017 02:47 PM, Richard Smith wrote:
> On 21 Mar 2017 12:23 pm, "Chandler Carruth" <chandlerc at gmail.com 
> <mailto:chandlerc at gmail.com>> wrote:
>
>     On Tue, Mar 21, 2017 at 6:06 PM Hal Finkel via cfe-dev
>     <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
>
>
>         On 03/21/2017 08:45 AM, Hubert Tong wrote:
>>         This question was explored in an other context here:
>>         http://sourcerytools.com/pipermail/cxx-abi-dev/2013-January/002544.html
>>         <http://sourcerytools.com/pipermail/cxx-abi-dev/2013-January/002544.html>
>
>         Very interesting, thanks! So the conclusion was that, " The
>         ABI will need to specify the layout of closure types with weak
>         linkage."
>
>
>     Are you basing that on what the document does or the discussion in
>     the thread? Because I don't really see a conclusion in the thread.
>     I see John pointing out three options and suggestion one which is
>     not what you claim is the conclusion here:
>     http://sourcerytools.com/pipermail/cxx-abi-dev/2013-January/002544.html
>     <http://sourcerytools.com/pipermail/cxx-abi-dev/2013-January/002544.html>
>
>     I don't see any real disagreement but I also don't see any real
>     discussion past that email and brief follow-ups....
>
>
> I expect John's #1 is most likely to be the eventual outcome; #2 and 
> #3 are too restrictive. Plus the language is moving in a direction 
> that makes the capture set much easier to reliably compute, so the 
> cost of #1 is going to become much more like "don't do those 
> optimisations you weren't really doing much anyway" and much less 
> "accurately implement these arcane and formally unobservable rules or 
> you violate the ABI".

The follow-up message is not linked properly in the web archive: 
http://sourcerytools.com/pipermail/cxx-abi-dev/2013-September/002618.html 
- Hubert wrote, " CWG has taken the position that issue CA 2 on this 
topic in N3771 is NAD. The ABI will need to specify the layout of 
closure types with weak linkage."

  -Hal

-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory

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