From db116b1ea3c77a3c5850fccbce9e0795faa21dda Mon Sep 17 00:00:00 2001 From: David Brownell Date: Thu, 5 Nov 2009 21:59:39 -0800 Subject: target: provide container_of() Provide a cleaner way to handle single inheritance of targets in C, using the same model Linux does: structs containing other structs, un-nested via calls to a "container_of()" macro that are packaged in typesafe inline functions. Targets already use this containment idiom, but make it much more complicated because they un-nest using embedded "void *" pointers ... in chains of up to five per target, which is all pure needless complication. (Example: arm92x core, arm9tdmi, arm7_9, armv4_5 ... on top of the base "target" class.) Applying this scheme consistently simplifies things, and gets rid of many error-prone untyped pointers. It won't change any part of the type model though -- it just simplifies things. (And facilitates more cleanup later on.) Rule of thumb: where there's an X->arch_info void* pointer, access to that pointer can and should be removed. It may be convenient to set up pointers to some of the embedded structs; and shrink their current "*_common" names (annoyingly long). Signed-off-by: David Brownell --- src/target/target.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) (limited to 'src/target/target.h') diff --git a/src/target/target.h b/src/target/target.h index c971f18b..1bbf40f0 100644 --- a/src/target/target.h +++ b/src/target/target.h @@ -26,6 +26,8 @@ #ifndef TARGET_H #define TARGET_H +#include + #include "breakpoints.h" #include "algorithm.h" #include "command.h" @@ -34,6 +36,19 @@ struct reg_s; struct trace_s; struct command_context_s; + +/** + * Cast a member of a structure out to the containing structure. + * @param ptr The pointer to the member. + * @param type The type of the container struct this is embedded in. + * @param member The name of the member within the struct. + * + * This is a mechanism which is used throughout the Linux kernel. + */ +#define container_of(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) );}) + /* * TARGET_UNKNOWN = 0: we don't know anything about the target yet * TARGET_RUNNING = 1: the target is executing user code -- cgit v1.2.3