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... -Kees -- Kees Cook
