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Re: [API] r18266

From: Julian Foad <julianfoad_at_btopenworld.com>
Date: 2006-02-02 23:08:53 CET

Peter N. Lundblad wrote:
> On Thu, 2 Feb 2006, Julian Foad wrote:
>>Peter N. Lundblad wrote:
>>
>>>I don't understand the above. If we forbid users to allocate this struct,
>>>we can freely add fields in the future without problems. Or do you mean
>>>that we have a rule that if you compile with library x+1, and it links
>>>with lbirary x, it should work? Is that what you mean by "forward
>>>compatibility"?
>>
>>Yes, that's what I meant.
>
> Is that really something we need to care about? If you link against 1.4.17
> and then, at runtime, use 1.3.4, could you expect that to work, then? I
> don't think we leave such guarantees.

Ah, yes, you're right. An application for 1.4.x libraries is not expected to
work when run with 1.3.x libraries, so we can add extra fields in the next
minor version, and don't care that an application using them won't work if run
with older libraries.

The difference from our normal API compatibility process is that in this case
the incompatibility won't be detected at link time. If a particular
application uses some features of the new library, but only ones of this kind,
then it will load and start to run against old libraries but with undefined
behaviour. I don't know whether we want to care about that.

I think the question is not specific to this patch, so I've committed it as
r18322 (with the caller updated too, of course - the patch I posted was
incomplete).

- Julian

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Received on Thu Feb 2 23:09:37 2006

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