this sort of thing can get problematic quickly.
the combinatorial explosion of cache-line design, memory design,
language alignment rules, architectures allowing non-aligned references
(but punishing you with slowness) makes testing hard.

on the other hand, starting on a 8 byte boundary is always a good idea in modern architectures.

better style is to use a byte stream so you won't get bitten by LSB/MSB issues
or packets coming from other machine architectures.

andrew

On Aug 4, 2010, at 1:09 PM, Pieter Hintjens wrote:

Matt,

I don't think this has been covered.  It would be sensible to have
vsm_data aligned but it's something that is IMO worth testing rather
than doing on faith.

-Pieter

Sorry if this has been covered before.
I've been using zmq to transport raw structures, and I've noticed that
zeromq apparently does not provide appropriate alignment for messages in
VSMs, and maybe for larger messages as well if you're using the front of the
content buffer (I haven't looked :-( )
Here are the offsets:

0x00    void *content;
0x08    unsigned char flags;
0x09    unsigned char vsm_size;
0x0a    unsigned char vsm_data [ZMQ_MAX_VSM_SIZE];

Shouldn't vsm_data be padded to 0x10 on 64 bit architectures (and maybe
others)?
RSVP,
Thanks,
Matt

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Andrew Hume  (best -> Telework) +1 732-886-1886
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