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Re: [libvirt] [PATCH] qemu: Add missing VIR_DOMAIN_BLOCK_COMMIT_DELETE flags



On 08/27/2013 03:37 AM, Michal Privoznik wrote:

>> Yes, the codes haven't any implementation for BLOCK_COMMIT_DELETE flag
>> now, maybe, only need to raise a friendly error message in here instead
>> of "unsupported flags (0x2) xxxx".
> 
> I agree that this error message is not user-friendly. Bare virsh users
> know nothing about our flags and their numerical expression. However, I
> don't think there is a way how to produce "Unsupported flag
> VIR_DOMAIN_BLOCK_COMMIT_DELETE" instead of "Unsupported flag 0x2" since
> all we see in the qemuDomainBlockCommit() function is just number. I
> mean, mapping of flag onto numeric value is not one-to-one function (aka
> injective function). That is, a value 0x2 can express
> VIR_DOMAIN_BLOCK_COMMIT_DELETE, VIR_DOMAIN_START_AUTODESTROY,
> VIR_DUMP_DESTROY, etc. (git grep "1 << 1," include/).
> 
> If we want to make it work, we have to introduce an injective function,
> e.g. virUnsupportedFlags(), which would accept a list (not an ORed
> value) of all flags that are not supported. Too much effort for not much
> outcome.

Agreed - it may not be the nicest of messages, but it is a CORRECT
message, and one that will eventually go away when we actually implement
things, so it isn't worth the churn of making a temporarily "nicer"
message just to rip it back out later when things are properly implemented.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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