wintrust/tests: Fix build with MSVC.

[David Laight]

On Thu, Jun 21, 2012 at 12:56:43PM +0200, Thomas Faber wrote:
> On 2012-06-21 12:34, Dmitry Timoshkov wrote:
> 
> > Thomas Faber <thfabba at gmx.de> wrote:
> > 
> >> FIELD_OFFSET isn't constant "enough".
> > 
> > The problem is not with FIELD_OFFSET, but with applying shift and mask
> > operations to a constant.
> 
> 
> You're right, it's actually a combination of multiple factors. I'm not sure
> what exactly its problem is - the gist is, FIELD_OFFSET cannot reliably be
> assumed constant.
> 
> E.g. the following code only complains about c4:
> 
> struct a {
>     char a;
>     int b[5];
>     int c;
> };
> int c1 = (int)&(((struct a *)0)->a) << 8;
> int c2 = (int)&(((struct a *)0)->b[0]);
> int c3 = (int)&(((struct a *)0)->b[0]) + 1;
> int c4 = (int)&(((struct a *)0)->b[0]) << 8;

This is a bug in the microsoft C compiler.
It won't let you do multiply or divide offsetof(struct, array_member[index])
by anything and still get a compile-time constant.
The C language requires offsetof() be a compile-time constant, so this
ought to be allowed.
I couldn't find anything that looked like 'offsetof' that would generate
a real compile-time constant.

I can't remember whether it is 'constant enough' to let you do:
    static char fubar[offsetof(struct a, b[3])];

	David

-- 
David Laight: david at l8s.co.uk