From 18aa4c8a2708c5f476ffa453b78594e3a00b52e9 Mon Sep 17 00:00:00 2001 From: Richard Qin Date: Sat, 10 Oct 2026 01:17:15 +0800 Subject: Add lab03 initial files Signed-off-by: Richard Qin --- lab03/container_of.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 49 insertions(+) create mode 100644 lab03/container_of.h (limited to 'lab03/container_of.h') diff --git a/lab03/container_of.h b/lab03/container_of.h new file mode 100644 index 0000000..bffe7b7 --- /dev/null +++ b/lab03/container_of.h @@ -0,0 +1,49 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/** + * @file container_of.h + * @brief Provides type-aware container and member offset macros. + */ +#ifndef _CONTAINER_OF_H +#define _CONTAINER_OF_H + +#include + +/** @brief Checks whether two expressions have compatible types. */ +#define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b)) + +/** @brief Computes a member offset using the compiler builtin. */ +#undef offsetof +#define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER) + +/** @brief Obtains the type of a member of a structure type. */ +#define typeof_member(T, m) typeof(((T*)0)->m) + +/** + * @brief Converts a pointer to a structure member to its containing object. + * @param ptr A pointer to the member. + * @param type The type of the containing structure. + * @param member The member name within `type`. + * + * The macro performs a compile-time type compatibility check before applying + * the member offset. + */ +#define container_of(ptr, type, member) ({ \ + _Static_assert(__same_type(*(ptr), typeof_member(type, member)) || \ + __same_type(*(ptr), void), \ + "pointer type mismatch in container_of()"); \ + (type *)((void *)(ptr) - offsetof(type, member)); }) + + +/** + * @brief Converts a member pointer while preserving its const qualification. + * @param ptr A pointer to the member. + * @param type The type of the containing structure. + * @param member The member name within `type`. + */ +#define container_of_const(ptr, type, member) \ + _Generic(ptr, \ + const typeof(*(ptr)) *: ((const type *)container_of(ptr, type, member)),\ + default: ((type *)container_of(ptr, type, member)) \ + ) + +#endif /* _CONTAINER_OF_H */ -- cgit v1.2.3