Storable laws

Henning Thielemann lemming at
Sat Dec 16 15:45:59 UTC 2017

On Sat, 16 Dec 2017, Sven Panne wrote:

> 2017-12-16 15:16 GMT+01:00 Henning Thielemann <lemming at>:
>       I thought that arrays require alignment of their elements.
> Yes, and if you start aligned, the pokeElemOff law keeps you aligned. If you don't start aligned, Storable never
> magically aligns the first element, anyway, so this must have been intentional (e.g. an array within packed
> data).
> In theory one could have an e.g. 7-byte data type with 8-byte alignment requirements, but I think we can re-open
> the discussion when a processor manufacturer is masochistic enough to do that. ;-)

I more think of a custom struct with size 12 bytes consisting of a 64 bit 
and 32 bit word. It must be 8-byte aligned. You would have to align all 
elements at multiples of 8-byte and the address difference between two 
array elements is 16 not 12.

On x86 Linux there would be no problem because a 12 byte struct containing 
a 64 bit word must already be padded to 16 byte. But that's an ABI 
definition and Storable wants to keep independent from that, right?

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