On Thu, 22 Feb 2024 at 04:10, 'Justin Stitt' via KUnit Development <kunit-dev@xxxxxxxxxxxxxxxx> wrote: > > Hi, > > On Wed, Feb 21, 2024 at 05:27:15PM +0800, David Gow wrote: > > The correct format specifier for p - n (both p and n are pointers) is > > %td, as the type should be ptrdiff_t. > > I think %tu is better. d specifies a signed type. I don't doubt that the > warning is fixed but I think %tu represents the type semantics here. > While I agree that this should never be negative, I'd still lean on this being a signed type, for two reasons: - I think, if there's a bug in this code, it's easier to debug this if a 'negative' value were to appear as such. - While, as I understand it, the C spec does provide for a ptrdiff_t-sized unsigned printf specifier in '%tu', the difference between two pointers is always signed: "When two pointers are subtracted, both shall point to elements of the same array object, or one past the last element of the array object; the result is the difference of the subscripts of the two array elements. The size of the result is implementation-defined, and its type (a signed integer type) is ptrdiff_t defined in the <stddef.h> header" (Technically, the kernel's ptrdiff_t type isn't defined in stddef.h, so a bit of deviation from the spec is happening anyway, though.) If there's a particularly good reason to make this unsigned in this case, I'd be happy to change it, of course. But I'd otherwise prefer to keep it as-is. Cheers, -- David
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