From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxx> > Sent: 28 July 2024 21:32 > > On Sun, 28 Jul 2024 at 13:23, David Laight <David.Laight@xxxxxxxxxx> wrote: > > > > MIN() (and probably your MIN_T()) ought to have a check for > > being a constant in order to stop misuse. > > No, we have a number of "runtime constants" that are basically > "constants" set up at boot-time for the architecture,as pointed out by > the powerpc people in private: > > Ie, we have arch/powerpc/include/asm/page.h: > > #define HPAGE_SHIFT hpage_shift > > and then > > #define HUGETLB_PAGE_ORDER (HPAGE_SHIFT - PAGE_SHIFT) > > and then > > #define pageblock_order MIN_T(unsigned int, > HUGETLB_PAGE_ORDER, MAX_PAGE_ORDER) > > and we really *REALLY* don't want to force the complicated "min_t()" > (or, worse yet, "min()") functions here just because there's actually > a variable involved. > > That variable gets initialized early in > hugetlbpage_init_defaultsize(), so it's *effectively* a constant, but > not as far as the compiler is concerned. Ok, but those can't be used as array sizes or constants. So the temporaries don't matter. Don't they just work with min() - if not where is the signednes mismatch? Perhaps we want: min() - temporaries, signedness check. min_t() - temporaries of given type, maybe check size not reduced? MIN() - no temporaries, no signedness check, only valid for constants. _min() - temporaries, no signedness check. _MIN() - no temporaries, no signedness check, variables allowed. I'm not sure where your MIN_T() fits in the above. Personally I think min_t() was a mistake. Only one input can need a cast and an explicit cast would be safer. David > > Linus - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
