Enforcing certain data structure explicit paddings.

Implicit paddings have undefined values in C. We want the eattr blocks
to be comparable by memcmp and eattrs settable directly by structrure
literals. This check ensures that all paddings in eattr and bval are
explicit and therefore zeroed in all literals.

1 files changed, 15 insertions, 3 deletions

diff --git a/lib/birdlib.h b/lib/birdlib.h
index 6f0bab96..9b6e4a16 100644
--- a/lib/birdlib.h
+++ b/lib/birdlib.h
@@ -9,18 +9,30 @@
 #ifndef _BIRD_BIRDLIB_H_
 #define _BIRD_BIRDLIB_H_
 
+#include "sysdep/config.h"
 #include "lib/alloca.h"
 
 /* Ugly structure offset handling macros */
 
-struct align_probe { char x; long int y; };
-
 #define OFFSETOF(s, i) ((size_t) &((s *)0)->i)
 #define SKIP_BACK(s, i, p) ((s *)((char *)p - OFFSETOF(s, i)))
 #define BIRD_ALIGN(s, a) (((s)+a-1)&~(a-1))
-#define CPU_STRUCT_ALIGN (sizeof(struct align_probe))
+#define CPU_STRUCT_ALIGN  (MAX_(_Alignof(void*), _Alignof(u64)))
 #define BIRD_CPU_ALIGN(s) BIRD_ALIGN((s), CPU_STRUCT_ALIGN)
 
+/* Structure item alignment macros */
+
+#define PADDING_NAME(id)	_padding_##id
+#define PADDING_(id, sz)	u8 PADDING_NAME(id)[sz]
+
+#if CPU_POINTER_ALIGNMENT == 4
+#define PADDING(id, n32, n64)	PADDING_(id, n32)
+#elif CPU_POINTER_ALIGNMENT == 8
+#define PADDING(id, n32, n64)	PADDING_(id, n64)
+#else
+#error "Strange CPU pointer alignment: " CPU_POINTER_ALIGNMENT
+#endif
+
 /* Utility macros */
 
 #define MIN_(a,b) (((a)<(b))?(a):(b))