On March 7, 2025 11:53:10 AM PST, David Laight <david.laight.linux@xxxxxxxxx> wrote: >On Fri, 07 Mar 2025 11:30:35 -0800 >"H. Peter Anvin" <hpa@xxxxxxxxx> wrote: > >> On March 7, 2025 10:49:56 AM PST, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: >> >> (int)true most definitely is guaranteed to be 1. >> > >> >That's not technically correct any more. >> > >> >GCC has introduced hardened bools that intentionally have bit patterns >> >other than 0 and 1. >> > >> >https://gcc.gnu.org/gcc-14/changes.html >> > >> >~Andrew >> >> Bit patterns in memory maybe (not that I can see the Linux kernel using them) but >> for compiler-generated conversations that's still a given, or the manager isn't C >> or anything even remotely like it. >> > >The whole idea of 'bool' is pretty much broken by design. >The underlying problem is that values other than 'true' and 'false' can >always get into 'bool' variables. > >Once that has happened it is all fubar. > >Trying to sanitise a value with (say): >int f(bool v) >{ > return (int)v & 1; >} >just doesn't work (see https://www.godbolt.org/z/MEndP3q9j) > >I really don't see how using (say) 0xaa and 0x55 helps. >What happens if the value is wrong? a trap or exception?, good luck recovering >from that. > > David Did you just discover GIGO?
