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Subject: Re: [std-proposals] std::error magic function
From: Michał Policht (michal_at_[hidden])
Date: 2020-03-26 03:14:42


>From your paper:
> However, a general issue is that constant expressions cannot report
errors when failure would occur

Isn't `static_assert` a mechanism, which allows constant expressions to
report errors?

Regards,
Michał

> I've done some work on this, and wrote a draft paper
> <https://github.com/chorman0773/CXX-Papers/blob/master/std_error_function.md>.
> I am interested in any feedback.
> I decided on a similar function, std::compiler_error, which has the same
> compile time behavior, but its UB at runtime. This would allow users to
> write std::error, with whatever runtime behavior they wish. 
> I would be interested in any feedback people have, both on the
> semantics, and in the structure of the paper itself. 
> Thank you to the great people on the std-proposals mailing list.
>
> On Fri, 6 Mar 2020 at 11:07, connor horman <chorman64_at_[hidden]
> <mailto:chorman64_at_[hidden]>> wrote:
>
> constinit won't downgrade (as the standard requires a constant
> expression initializer). I did forget about that.
>
> On Fri, 6 Mar 2020 at 10:13, Thiago Macieira via Std-Proposals
> <std-proposals_at_[hidden]
> <mailto:std-proposals_at_[hidden]>> wrote:
>
> On Friday, 6 March 2020 06:46:56 PST connor horman via
> Std-Proposals wrote:
> > Currently it is not possible to implement std::error in a way
> that it will
> > work with initializing non-constexpr variables. Throwing an
> exception
> > simply downgrades to runtime, only erroring if the result is
> needed at
> > compile time.
>
> Does that also apply to constinit variables?
>
> --
> Thiago Macieira - thiago (AT) macieira.info
> <http://macieira.info> - thiago (AT) kde.org <http://kde.org>
>    Software Architect - Intel System Software Products
>
>
>
> --
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>


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