Re: [boost] [outcome v2] ntkernel_category() custom error category appropriate for Outcome?

Subject: Re: [boost] [outcome v2] ntkernel_category() custom error category appropriate for Outcome?
From: Gavin Lambert (gavinl_at_[hidden])
Date: 2017-07-21 00:24:23

On 21/07/2017 11:02, Niall Douglas via Boost wrote:
> I put together a custom `std::error_category` for NT kernel `NTSTATUS`
> error codes with error condition comparison support for both POSIX and
> Win32 error code spaces:
> 
> https://github.com/ned14/ntkernel-error-category

I do like that this allows interpretation of NTSTATUS codes on 
non-Windows, although the chances of actually encountering one in that 
case seems rather slim (unless maybe CIFS APIs expose the raw server 
status code).

> Question: Is this custom `std::error_category` so niche and unlikely to
> be useful to anybody that people would object to it being supplied in
> Outcome v2?

Isn't Outcome v2 header-only?

It seems weird to add this to it in that case (because this prefers to 
build as a shared library).

Much as it seems cumbersome to have such a small library be standalone, 
I think that might be the better choice, rather than changing a 
completely-header-only library into an only-kinda-header-only library.

On the other hand, the exported-inline pattern *does* work (at least on 
Windows) to make real singletons between shared libraries even from 
header-only -- you just need to let the user pick one library to export 
the definition and ensure all consumers of that library import it. 
Presumably Linux/gcc has an equivalent?