#include <os/alloc_util.h>

os/alloc_util.h Kernel.framework

@macro os_is_ptr_like @abstract Tell whether the given expression resembles a pointer. @discussion When pointer bounds are enabled, only types that are actually classified as pointers will be considered pointer-like. Otherwise, any pointer-sized type will be considered pointer-like. @param P the expression to be checked

includes: sys/cdefs.h, os/cpp_util.h

3 macros

macroos_is_ptr_like

#define os_is_ptr_like(P) /* NOLINTNEXTLINE(bugprone-sizeof-expression) */
	(sizeof(P) == sizeof(void *))

macroos_ptr_load_and_erase

@macro os_ptr_load_and_erase @abstract Load the value of @c elem into a temporary, set @c elem to NULL, and return the value. @param elem the pointer whose value will be taken, and which will be set to NULL.

#define os_ptr_load_and_erase(elem) ({
	_Static_assert(os_is_ptr_like(elem),
	    "elem isn't pointer sized");
	__auto_type *__single __eptr = &(elem);
	__auto_type __elem = *__eptr;
	_Pragma("clang diagnostic push")
	_Pragma("clang diagnostic ignored \"-Wold-style-cast\"")
	*__eptr = (__typeof__(__elem))NULL;
	_Pragma("clang diagnostic pop")
	__elem;
})

macroos_get_pointee_type

The reason we're using the compiler builtins is that those are able to properly deal with __ptrauth-qualified pointers, unlike template specializations. Moreover, template specializations would require forwarding type definitions, and currently __attribute__((xnu_usage_semantics(...))) annotations are not carried over across typedefs. It is safe to assume that if the compiler does not support such builtins, it also does not implement D150875, and we can therefore safely dereference void pointers.

#define os_get_pointee_type(ptr) __remove_pointer(__remove_reference_t(__typeof__(ptr)))