From 17e42975c2d42574072925f3743cc64bfd5a8fc1 Mon Sep 17 00:00:00 2001 From: Ben Pfaff Date: Wed, 17 Nov 2010 12:34:42 -0800 Subject: [PATCH] util: Improve type-safety of OBJECT_CONTAINING. --- lib/util.h | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) diff --git a/lib/util.h b/lib/util.h index 703b93cf..29e212dc 100644 --- a/lib/util.h +++ b/lib/util.h @@ -77,20 +77,29 @@ extern const char *program_name; #define NOT_REACHED() abort() +/* Given a pointer-typed lvalue OBJECT, expands to a pointer type that may be + * assigned to OBJECT. */ +#ifdef __GNUC__ +#define OVS_TYPEOF(OBJECT) typeof(OBJECT) +#else +#define OVS_TYPEOF(OBJECT) void * +#endif + /* Given POINTER, the address of the given MEMBER in a STRUCT object, returns the STRUCT object. */ #define CONTAINER_OF(POINTER, STRUCT, MEMBER) \ ((STRUCT *) (void *) ((char *) (POINTER) - offsetof (STRUCT, MEMBER))) /* Given POINTER, the address of the given MEMBER within an object of the type - * that that OBJECT points to, returns OBJECT as a "void *" pointer. OBJECT - * must be an lvalue. + * that that OBJECT points to, returns OBJECT as an assignment-compatible + * pointer type (either the correct pointer type or "void *"). OBJECT must be + * an lvalue. * * This is the same as CONTAINER_OF except that it infers the structure type * from the type of '*OBJECT'. */ #define OBJECT_CONTAINING(POINTER, OBJECT, MEMBER) \ - ((void *) ((char *) (POINTER) \ - - ((char *) &(OBJECT)->MEMBER - (char *) (OBJECT)))) + ((OVS_TYPEOF(OBJECT)) (void *) \ + ((char *) (POINTER) - ((char *) &(OBJECT)->MEMBER - (char *) (OBJECT)))) #ifdef __cplusplus extern "C" { -- 2.30.2