On Wed, 2019-12-04 at 15:41 +0100, Klaus Doldinger wrote: > > Am 04.12.19 um 15:33 schrieb Oleg Endo: > > On Wed, 2019-12-04 at 14:50 +0100, Klaus Doldinger wrote: > > > Hello, > > > > > > does anybody see a possibility to perform a compiletime-check to > > > verify > > > that a bit of a bit-field is at an exact position of the > > > underlying type? > > > > > > I would see a possible using the forecoming std::bit_cast, but > > > what can > > > one do with c++17? > > > > > > > Perhaps have a look at this approach > > https://blog.codef00.com/2014/12/06/portable-bitfields-using-c11/ > > Well, I don't think this is correct, since reading/writing from a > non-active member of a union leads to UB. > So, I think the blog-post ist simply wrong. Right, it's UB ... although "most compilers implement it as non- standard extension". So I wouldn't say the blog post is wrong per se, it's just failing to mention a tiny detail :) Cheers, Oleg
