There is *NO* abi stability in -head

David Chisnall theraven at FreeBSD.org
Tue Oct 24 08:19:06 UTC 2017


On 23 Oct 2017, at 21:35, Mateusz Guzik <mjguzik at gmail.com> wrote:
> 
> Instead, the same can be reshuffled:
> struct crap2 {
>        int i1;
>        int i2;
>        void *p1;
>        void *p2;
> };
> 
> With offsets:
> 
> 0x1000 i1
> 0x1004 i2
> 0x1008 p1
> 0x1010 p2
> 
> This is only 24 bytes. 2 ints can be placed together and since they add
> up to 8 the p1 pointer gets the right alignment without extra padding.

If you are making changes of this nature, please consider sorting in the other order.  When we start seeing 128-bit pointers (which, with CHERI-like systems, may be sooner than you think) then this ordering will give you lots of padding, whereas putting the pointers first will not.

David



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