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

From: Gero Peterhoff (g.peterhoff_at_[hidden])
Date: 2022-08-21 20:26:42

Am 19.08.22 um 03:53 schrieb Proton via Boost:
> 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.

Hi Matt,
I see that you have started work on ccmath::signbit/copysign/etc. I also. Our basic problem is that std::bit_cast is only available with C++20. You are already trying to provide this for C++17 (BOOST_MATH_BIT_CAST). My questions:
- can you *guarantee* that BOOST_MATH_BIT_CAST works on/with all platforms/compilers ?
- if not: does it make sense to upgrade ccmath to C++20 so that std::bit_cast is available ?

Otherwise I can only oracle and provide code to the best of my knowledge - without guarantee that it works on/with all platforms/compilers :-(

regards
Gero