[ovs-dev] [urcu v2 02/15] compiler: New macro for defining aligned structs.

[Gurucharan Shetty]

On Tue, Mar 11, 2014 at 1:56 PM, Ben Pfaff <blp at nicira.com> wrote:
> 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 at nicira.com>
> Signed-off-by: Ben Pfaff <blp at nicira.com>

Looks good to me.

I do not see any users of it though.

The idea is to do something like this, right?

#define OVS_ALIGNED_STRUCT(N, TAG) __declspec(align(N)) struct TAG

struct test {
    int a;
    int b;
    char c;
};
OVS_ALIGNED_STRUCT(64, test);

Thanks,
Guru


> ---
>  lib/compiler.h |   16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/lib/compiler.h b/lib/compiler.h
> index e867d72..3b59813 100644
> --- 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)
> --
> 1.7.10.4
>