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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH 1/2] Add new input plugin UNIXSOCK
Date: Sun, 01 Nov 2009 22:22:49 -0800 (PST)
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From: Jan Engelhardt <jengelh@medozas.de>
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.