From: Russell King <[email protected]>
Date: Wed, 6 Dec 2006 17:54:23 +0000
> It does not say "and as such the struct may be aligned to any alignment".
Consider the implication for arrays and pointer arithmetic, it's just
a logical consequence, that's all. It's why the alignment cannot be
assumed for packed structures.
If you have, for example:
struct example {
char b;
short c;
} __attribute__((packed));
And I give you:
extern void foo(struct example *p);
and go:
foo(p + 1);
It is clear that the compiler must assume that all instances
of a packed structure are not necessarily aligned properly.
Even if "p" is aligned, "p + 1" definitely won't be. And this
goes for any array indexing of the given packed structure.
That's why every pointer to such a struct must be assumed to be
unaligned in these cases.
So even though the documentation may not say this explicitly, it's an
implicit logical side effect of packed structures.
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