https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110557
--- Comment #5 from avieira at gcc dot gnu.org --- Hi Xi, Feel free to test your patch and submit it to the list for review. I had a look over and it looks correct to me. I feel like it also addresses the cases where the bitfield is 'sandwiched' like: int x : 7; ptrdiff_t y : 56; long long z: 1; As you left-shift it, and it also addresses the case where you have both sign-extension and have to widen-it, because you still transform the type into signed. But it might be nice to add tests to cover those two, just in case someone changes this. In the future, if you do plan to work on something it would be nice to let people know on the bugzilla ticket (preferably by assigning it to yourself) so that multiple people don't end up working on the same thing, I had started to write a patch, but wasn't as far as you and I like your approach :)
