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Re: [Patch] [add changelog] reduce template instantiation depth in <variant>
On Sat, Nov 12, 2016 at 2:39 PM, Tim Shen <timshen@google.com> wrote:
> On Sat, Nov 12, 2016 at 4:28 AM, Daniel Krügler
> <daniel.kruegler@gmail.com> wrote:
>> 2016-11-12 10:04 GMT+01:00 Barrett Adair <barrettellisadair@gmail.com>:
>>>>Currently, std::variant exceeds the default ftemplate-depth parameter when instantiated with 297 types. This small patch increases this ceiling to 446 types (from the bottom of the template stack).
>>>
>>> Sorry, first patch - I just read the guidelines. I changed the format
>>> and added a changelog entry. I hope I did it correctly this time.
>>
>> Let me add that this patch suggestion causes a change in semantics in
>> theory, because fold expressions have no short-circuit evaluation,
>
> Is it a compiler QoI problem, or part of the language? I'd be
> surprised if the language somehow prohibits the short circuits from
> happening.
>
>> contrary to __and_. Whether this difference is relevant here is
>> of-course something the maintainer has to decide.
>>
Since there are no side-effects, and the metafunctions in play cannot
SFINAE, I don't believe the semantics are actually affected by
short-circuiting in this case.