Hi, A couple of extra notes on my patch.
On Sun, Aug 26, 2018 at 7:57 PM, Miguel Ojeda <miguel.ojeda.sando...@gmail.com> wrote: > +/* > + * Optional attributes: your compiler may or may not support them. > + * > + * To check for them, we use __has_attribute, which is supported on gcc >= 5, > + * clang >= 2.9 and icc >= 17. In the meantime, to support 4.6 <= gcc < 5, > + * we implement it by hand. > + */ > +#ifndef __has_attribute > +#define __has_attribute(x) __GCC46_has_attribute_##x > +#define __GCC46_has_attribute_assume_aligned 0 > +#define __GCC46_has_attribute_designated_init 0 > +#define __GCC46_has_attribute_externally_visible 1 > +#define __GCC46_has_attribute_noclone 1 > +#define __GCC46_has_attribute_optimize 1 > +#define __GCC46_has_attribute_no_sanitize_address 0 Note that: - assume_aligned came with gcc 4.9 - no_sanitize_address came with gcc 4.8 So if we feel it is important to have them there (before gcc 5), we would need here a quick version check here. > +#endif > + > +/* > + * __assume_aligned(n, k): Tell the optimizer that the returned > + * pointer can be assumed to be k modulo n. The second argument is > + * optional (default 0), so we use a variadic macro to make the > + * shorthand. > + * > + * Beware: Do not apply this to functions which may return > + * ERR_PTRs. Also, it is probably unwise to apply it to functions > + * returning extra information in the low bits (but in that case the > + * compiler should see some alignment anyway, when the return value is > + * massaged by 'flags = ptr & 3; ptr &= ~3;'). > + */ > +#if __has_attribute(assume_aligned) > +#define __assume_aligned(a, ...) __attribute__((assume_aligned(a, ## > __VA_ARGS__))) > +#else > +#define __assume_aligned(a, ...) > +#endif Beforehand, these were !defined(__CHECKER__). I am not sure if sparse complains too much about it. Maybe sparse could learn __has_attribute. Cheers, Miguel
