Re: [boost] [outcome] Review of Outcome

Subject: Re: [boost] [outcome] Review of Outcome
From: Peter Dimov (lists_at_[hidden])
Date: 2017-05-28 23:59:48

Niall Douglas wrote:
> ```
> result<void> function(std::vector<Foo> &a) noexcept
> {
>   try
>   {
>     a.push_back(Foo());
>   }
>   BOOST_OUTCOME_CATCH_EXCEPTION_TO_RESULT
> }
> ```
>
> Here vector.push_back() might throw a std::bad_alloc. Under optimisation, 
> the above code converts the throw of std::bad_alloc into a branch to early 
> exit of an errored result<void>. So the exception throw and catch 
> machinery is completely removed, and replaced with a fast branch. A very 
> big win.

Unfortunately not. I expected this to be the case, but on the compilers I 
tested recently, the throw is not removed. Apparently the compilers consider 
the call to __cxa_throw observable behavior and never elide it. What 
compiler did?

(I'll get back to the rest of your message later.)