Messages in this thread | | | Date | Tue, 31 Dec 2013 08:27:02 -0800 | From | Ben Greear <> | Subject | Re: [PATCH 4/11] use ether_addr_equal_64bits |
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On 12/31/2013 08:09 AM, Julia Lawall wrote: > > > On Tue, 31 Dec 2013, Ben Greear wrote: > >> On 12/30/2013 10:32 PM, Julia Lawall wrote: >>>>>>> I'm just thinking of a programmer, e.g. changing a struct like this: >>>>>>> >>>>>>> struct foo { >>>>>>> u8 addr[ETH_ALEN]; >>>>>>> - u16 dummy; >>>>>>> }; >>>> >>>> I don't know of a way to catch that. >>>> Anyone else? >>> >>> Well, one could have a semantic patch that checks for that. But the >>> problem is that it is very slow, and it only covers the cases that I can >>> transform automatically, which currently means no pointers, only explicit >>> arrays. >>> >>> On the other hand, I am finding the structure definition, so I can easily >>> update the structure definition with an appropriate comment. >>> >>> struct foo { >>> u8 addr[ETH_ALEN]; /* must be followed by two bytes in the structure */ >>> u16 dummy; >>> }; >>> >>> Unfortunately it is kind of verbose. Could there be an attribute? That >>> could even easily be checked. >> >> Can you not just add a build-time macro to check that sizeof(foo) >= 8 >> for each of these struct foos? Or, is it required that the dummy field >> be there and be not used by anything else? > > It doesn't matter what the field is used for. The problem is that is it > necessary to ensure a property of the position of addr within the > structure. It has to have at least 16 bytes after it.
You mean 16 bits?
> > But maybe something with sizeof(foo) and offset_of would do? > > Could the macro be put near the declaration of the structure somehow?
I think that would work, but do not know all of the details of such macros, so it's possible there is some catch.
If nothing else, then some run-time code that calculates the offset off and asserts if it is broken in module initialization or similar might be good enough.
Thanks, Ben
-- Ben Greear <greearb@candelatech.com> Candela Technologies Inc http://www.candelatech.com
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