On March 7, 2025 11:30:08 AM PST, Yury Norov <yury.norov@xxxxxxxxx> wrote: >On Fri, Mar 07, 2025 at 04:14:34AM -0800, H. Peter Anvin wrote: >> On March 7, 2025 4:13:26 AM PST, Ingo Molnar <mingo@xxxxxxxxxx> wrote: >> > >> >* Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: >> > >> >> On 07. 03. 25, 12:38, Ingo Molnar wrote: >> >> > >> >> > * Jiri Slaby <jirislaby@xxxxxxxxxx> wrote: >> >> > >> >> > > On 06. 03. 25, 17:25, Kuan-Wei Chiu wrote: >> >> > > > Change return type to bool for better clarity. Update the kernel doc >> >> > > > comment accordingly, including fixing "@value" to "@val" and adjusting >> >> > > > examples. Also mark the function with __attribute_const__ to allow >> >> > > > potential compiler optimizations. >> >> > > > >> >> > > > Co-developed-by: Yu-Chun Lin <eleanor15x@xxxxxxxxx> >> >> > > > Signed-off-by: Yu-Chun Lin <eleanor15x@xxxxxxxxx> >> >> > > > Signed-off-by: Kuan-Wei Chiu <visitorckw@xxxxxxxxx> >> >> > > > --- >> >> > > > include/linux/bitops.h | 10 +++++----- >> >> > > > 1 file changed, 5 insertions(+), 5 deletions(-) >> >> > > > >> >> > > > diff --git a/include/linux/bitops.h b/include/linux/bitops.h >> >> > > > index c1cb53cf2f0f..44e5765b8bec 100644 >> >> > > > --- a/include/linux/bitops.h >> >> > > > +++ b/include/linux/bitops.h >> >> > > > @@ -231,26 +231,26 @@ static inline int get_count_order_long(unsigned long l) >> >> > > > /** >> >> > > > * parity8 - get the parity of an u8 value >> >> > > > - * @value: the value to be examined >> >> > > > + * @val: the value to be examined >> >> > > > * >> >> > > > * Determine the parity of the u8 argument. >> >> > > > * >> >> > > > * Returns: >> >> > > > - * 0 for even parity, 1 for odd parity >> >> > > > + * false for even parity, true for odd parity >> >> > > >> >> > > This occurs somehow inverted to me. When something is in parity means that >> >> > > it has equal number of 1s and 0s. I.e. return true for even distribution. >> >> > > Dunno what others think? Or perhaps this should be dubbed odd_parity() when >> >> > > bool is returned? Then you'd return true for odd. >> >> > >> >> > OTOH: >> >> > >> >> > - '0' is an even number and is returned for even parity, >> >> > - '1' is an odd number and is returned for odd parity. >> >> >> >> Yes, that used to make sense for me. For bool/true/false, it no longer does. >> >> But as I wrote, it might be only me... >> > >> >No strong opinion on this from me either, I'd guess existing practice >> >with other parity functions should probably control. (If a coherent >> >praxis exists.). >> > >> >Thanks, >> > >> > Ingo >> >> Instead of "bool" think of it as "bit" and it makes more sense > >So, to help people thinking that way we can introduce a corresponding >type: > typedef unsigned _BitInt(1) u1; > >It already works for clang, and GCC is going to adopt it with std=c23. >We can make u1 an alias to bool for GCC for a while. If you guys like >it, I can send a patch. > >For clang it prints quite a nice overflow warning: > >tst.c:59:9: warning: implicit conversion from 'int' to 'u1' (aka 'unsigned _BitInt(1)') changes value from 2 to 0 [-Wconstant-conversion] > 59 | u1 r = 2; > | ~ ^ > >Thanks, >Yury No, for a whole bunch of reasons.
