Re: bug - boost::math::ccmath::copysign not work

From: Proton (matt_at_[hidden])
Date: 2022-08-19 01:53:36

> On Aug 18, 2022, at 5:26 AM, Andrey Semashev via Boost <boost_at_[hidden]> wrote:
>
> On 8/18/22 13:13, John Maddock via Boost wrote:
>> On 18/08/2022 07:23, Mathias Gaunard via Boost wrote:
>>> bit_cast is constexpr.
>>
>> Good catch!
>>
>> Matt and I discussed this ages ago and decided it was basically
>> impossible, it's a shame that fix is C++20 but it's certainly better
>> than nothing.
>
> __builtin_bit_cast is available regardless of the C++ level. Though
> you're still limited to compilers that support it.
>
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Using __builtin_bit_cast should be fine for conditional C++17 support since we already rely on __builtin_is_constant_evaluated. I’ll play with it this weekend and see where it get us. Worst case is we static_assert unsupported cases like John suggested.

Matt