Re: [boost] [hash][array][stacktrace][type_index] Adding noexcept to hash

Subject: Re: [boost] [hash][array][stacktrace][type_index] Adding noexcept to hash
From: Daniel James (dnljms_at_[hidden])
Date: 2017-12-04 08:57:24

On 4 December 2017 at 06:54, Richard Hodges via Boost
<boost_at_[hidden]> wrote:
> Adding a noexcept specification (i.e. making an interface more restrictive)
> sounds like a breaking change to me. Although it's the correct thing to do,
> surely anyone who has an override of hash_range in their code will be
> affected?

It isn't a member function, so there's no way to override it. The
customization point is a call to hash_value via argument dependent
lookup. The noexcept specifiers are going to be conditional on whether
the iterators and hash functions are noexcept, so if an overload
doesn't have a noexcept specification, then hash_range for that value
is going to be effectively noexcept(false) and will still be
compatible.