On Tue, 2021-09-21 at 16:37 -0700, Kees Cook wrote: > On Fri, Sep 10, 2021 at 10:23:48AM -0700, Linus Torvalds wrote: > > On Thu, Sep 9, 2021 at 8:10 PM Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote: > > > > > > +__alloc_size(1) > > > extern void *vmalloc(unsigned long size); > > [...] > > > > All of these are added in the wrong place - inconsistent with the very > > compiler documentation the patches add. > > > > The function attributes are generally added _after_ the function, > > although admittedly we've been quite confused here before. > > > > But the very compiler documentation you point to in the patch that > > adds these macros gives that as the examples both for gcc and clang: > > > > + * gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-alloc_005fsize-function-attribute > > + * clang: https://clang.llvm.org/docs/AttributeReference.html#alloc-size > > > > and honestly I think that is the preferred format because this is > > about the *function*, not about the return type. > > > > Do both placements work? Yes. > > I'm cleaning this up now, and have discovered that the reason for the > before-function placement is consistency with static inlines. If I do this: > > static __always_inline void * kmalloc(size_t size, gfp_t flags) __alloc_size(1) > { > ... > } > > GCC is very angry: > > ./include/linux/slab.h:519:1: error: attributes should be specified before the declarator in a function definition > 519 | static __always_inline void *kmalloc_large(size_t size, gfp_t flags) __alloc_size(1) > | ^~~~~~ > > It's happy if I treat it as a "return type attribute" in the ordering, > though: > > static __always_inline void * __alloc_size(1) kmalloc(size_t size, gfp_t flags) > > I'll do that unless you have a preference for somewhere else... _please_ put it before the return type on a separate line. [__attributes] [static inline const] <return type> function(<args...>)
