Re: [boost] expected/result/etc

Subject: Re: [boost] expected/result/etc
From: Niall Douglas (s_sourceforge_at_[hidden])
Date: 2016-01-29 08:27:02

On 28 Jan 2016 at 10:32, Michael Marcin wrote:

> If you are going to handle the error in non-generic code very close to 
> the caller, I contend there is no need to actually call make_error_code 
> and wrap that enum into a std::error_code. The enum is typically 4 
> bytes, a std::error_code is usually 16.
> 
> Certainly many times it doesn't matter at all but there are also times 
> where it would prevent me from having a good faith argument that this is 
> a strict improvement over a more C-style error handling approach.

Unlike exception_ptr, error_code has no global memory effects and is 
elidable by the optimiser. Assuming there are no calls to extern 
functions between the return of an error_code and the handling of it, 
you will find your nominal 16 bytes reduced to a direct test of the 
state of errno/GetLastError which is of course no overhead at all.

Niall

-- 
ned Productions Limited Consulting
http://www.nedproductions.biz/ 
http://ie.linkedin.com/in/nialldouglas/