Messages in this thread | | | Date | Fri, 4 Aug 2023 03:11:25 +0800 | Subject | Re: [PATCH v6 01/38] minmax: Add in_range() macro | From | Phi Nguyen <> |
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On 8/3/2023 9:22 PM, Matthew Wilcox wrote: > On Thu, Aug 03, 2023 at 09:00:35PM +0800, Phi Nguyen wrote: >> On 8/2/2023 11:13 PM, Matthew Wilcox (Oracle) wrote: >>> +static inline bool in_range64(u64 val, u64 start, u64 len) >>> +{ >>> + return (val - start) < len; >>> +} >>> + >>> +static inline bool in_range32(u32 val, u32 start, u32 len) >>> +{ >>> + return (val - start) < len; >>> +} >>> + >> >> I think these two functions return wrong result if val is smaller than start >> and len is big enough. > > How is it that you stopped reading at exactly the point where I explained > that this is intentional? > > +/** > + * in_range - Determine if a value lies within a range. > + * @val: Value to test. > + * @start: First value in range. > + * @len: Number of values in range. > + * > + * This is more efficient than "if (start <= val && val < (start + len))". > + * It also gives a different answer if @start + @len overflows the size of > + * the type by a sufficient amount to encompass @val. Decide for yourself > + * which behaviour you want, or prove that start + len never overflow. > + * Do not blindly replace one form with the other. > + */ >
Oh, sorry, I see, my bad.
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