From: Jan Engelhardt <jengelh@xxxxxxxxxx>
Date: Sun, 1 Nov 2009 14:41:21 +0100 (CET)
> +static inline uint32_t deref_get_32(const void *ptr)
> +{
> + uint32_t ret;
> + memcpy(&ret, ptr, sizeof(ret));
> + return ret;
> +}
>
> Is what I use in one project; however, trying to minimize the
> unalignedness - iptables is a "perfect" example, and netlink
> may do the same tho I am not sure - seems to be the best
> approach in serialized streams.
This will not work all the time.
If GCC can see at the inlining point that 'ptr' is of a type that
should be properly aligned it can inline the memcpy and still emit
the very unaligned load or store that you're trying to avoid.
Using a void pointer doesn't create a sort of "barrier" for typing
visibility like you think it does.
So I would argue against using this construct, because it only gives
you a false sense of security.
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