niekbouman/ctbignum

Using a bitshift with a shift larger than the limb bitwidth doesn't work

aldogunsing-rl opened this issue · 2 comments

aldogunsing-rl commented

Currently, shift_right (and probably shift_left as well) don't support a shift larger than the limb bitwidth and when used give an undefined result. It would be nice if this was supported, or at least checked so an error would be given whenever it is tried.

johnmcfarlane commented

Have you tried with UBSan enabled?

niekbouman commented

Currently, shift_right (and probably shift_left as well) don't support a shift larger than the limb bitwidth and when used give an undefined result. It would be nice if this was supported, or at least checked so an error would be given whenever it is tried.

Indeed. I have now clarified this in the inline documentation of those functions.

I could also add an assert statement to explicitly check this, but then consumers have to think of compiling with the NDEBUG flag in production builds. Would you prefer that?

BTW We do accept pull requests ;-)