Bug#642762: xulrunner-6.0: console flooded with unaligned access messages on ia64 (IA-64/IPF/Itanium) platform

[Émeric Maschino]

OK, reading http://www.osronline.com/ddkx/kmarch/64bitamd_20iv.htm
helped me understand structure alignment (well, I think!): "The
alignment of the beginning of a structure or a union is the maximum
alignment of any individual member."

> 2011/10/5 Mike Hommey <mh at glandium.org>:
> On Wed, Oct 05, 2011 at 10:50:56AM +0200,
>
> The problem is not the alignment of m2, the problem is the alignment of
> the whole struct, which has a requirement of 32-bits. Which means a
> struct nsID can end up at 0x0, 0x4, 0x8, or 0xc. When it's at 0x4 or
> 0xc, it can't be casted to a 64-bits word, because that's not 64-bits
> aligned. There are two solutions: make sure struct nsIDs are 64-bits
> aligned, or change the Equals function to use 2 32 bits words
> comparisons.

So, in order to have nsID 64-bit aligned, is simply inserting a
PRUint64 dummy internal data the way to enforce 64-bit alignment?

struct nsID {
  PRUint64 dummy;
  PRUint32 m0;
  PRUint16 m1;
  PRUint16 m2;
  PRUint8 m3[8];
};

     Emeric