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



On 08/27/2013 07:59 PM, Eric Blake wrote:
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.


Agree, it isn't worth changing a temporarily "nicer" message now.


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