On Wed, Jun 12, 2024 at 04:00:18PM +0200, Alejandro Colomar wrote: > Hi Greg, > > On Wed, Jun 12, 2024 at 03:35:20PM GMT, Greg KH wrote: > > On Wed, Jun 12, 2024 at 03:16:58PM +0200, Alejandro Colomar wrote: > > > Constants that are to be used in bitwise operations should be unsigned, > > > or a user could easily trigger Undefined Behavior. > > > > Wait, do we really have such broken compilers out there? > > I meant this as a generic statement that signed integers on bitwise ops > are bad, not as a specific statement that these values would trigger UB. > > I expect that these specific values and the operations done on them > probably don't trigger UB, since the shifts are done by a controlled > amount, and there are justa few operations done on them. These, for the most part, are NOT used as shifts. > For example, a left shift where a set bit overflows the type (e.g., > 1<<32), causes UB. Sure, but that's not in play here. > The reason why it's better to avoid this at all even if we know these > values work fine, is that programs using <asm/termbits.h> would need to > disable those compiler warnings, which could silence warnings on other > code which might be broken. But again, you aren't using these as bit shifts, they are bit masks, or values, only. > TL;DR: The kernel isn't broken, but improving this would allow users to > enable stricter warnings, which is a good thing. Enable it where? thanks, greg k-h
