compiler: New macro for defining aligned structs.

This is broken out into a separate commit because it adds new MSVC
specific code and I don't have MSVC around to test whether it's correct.

CC: Gurucharan Shetty <gshetty@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>

diff --git a/lib/compiler.h b/lib/compiler.h
index e867d72..3b59813 100644 (file)
--- a/lib/compiler.h
+++ b/lib/compiler.h
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013, 2014 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -179,6 +179,20 @@
 #define OVS_PACKED(DECL) __pragma(pack(push, 1)) DECL __pragma(pack(pop))
 #endif
 
+/* For defining a structure whose instances should aligned on an N-byte
+ * boundary.
+ *
+ * e.g. The following:
+ *     OVS_ALIGNED_STRUCT(64, mystruct) { ... };
+ * is equivalent to the following except that it specifies 64-byte alignment:
+ *     struct mystruct { ... };
+ */
+#ifndef _MSC_VER
+#define OVS_ALIGNED_STRUCT(N, TAG) struct __attribute__((aligned(N))) TAG
+#else
+#define OVS_ALIGNED_STRUCT(N, TAG) __declspec(align(N)) struct TAG
+#endif
+
 #ifdef _MSC_VER
 #define CCALL __cdecl
 #pragma section(".CRT$XCU",read)