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Re: [libvirt] [PATCH 2.5/7] maint: prefer newer API names internally

On 05/18/2011 10:55 AM, Daniel P. Berrange wrote:
>> Apps shouldn't be doing this (struct _virMemoryParameter is a private
>> name).  Furthermore, we already deleted that private name in patch 1/7;
>> applications using the private name will now be declaring an incomplete
>> type, which explains the warning you saw in your demo program.
> IMHO 'struct _virMemoryParameter' is just as much a public name
> as anything else in the public header file. The typedef serves as
> convenient syntactic sugar, but using either is valid for app
> developers, so we should not be deleting it.

Then I'm working on a patch to restore the missing names (I deleted
_virMemoryParameter, _virBlkioParameter, and _virSchedParameter).

>>> will get a compile warning/error
>>>   demo.c: In function ‘main’:
>>>   demo.c:35:3: warning: passing argument 2 of ‘virDomainGetSchedulerParameters’ from incompatible pointer type
>>>   demo.c:25:12: note: expected ‘virTypedParameterPtr’ but argument is of type ‘struct _virMemoryParameter *’
>>> so NACK to this change.
>> Even if you convince me to not change the public signatures of the
>> functions that existed prior to 0.9.2, I still think that it is worth
>> changing the signature of virDomainSetSchedulerFlags (since we haven't
>> released it yet), as well as all internal signatures.
> I think we could perhaps achieve the same cleanup using #defines instead
> of typedefs, which would avoid breaking app code.

Indeed, and I'll give that a shot for restoring the old names.

The goal here is ABI stability (the bits are the same, regardless of
when it was compiled - we have that) and API stability (recompiling
works without introducing new warnings or errors while using the old
names - patch 1/7 broke that for the leading _ names).

Eric Blake   eblake redhat com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

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