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.)