[libvirt] [libvirt-go PATCH 0/3] Introduce recent DomainSnapshotXML and DomainSaveImageXML flags

[Daniel P. Berrangé]

On Mon, Feb 25, 2019 at 12:42:58PM +0100, Erik Skultety wrote:
> On Mon, Feb 25, 2019 at 11:14:41AM +0000, Daniel P. Berrangé wrote:
> > On Mon, Feb 25, 2019 at 12:09:41PM +0100, Erik Skultety wrote:
> > > On Fri, Feb 22, 2019 at 04:43:25PM +0000, Daniel P. Berrangé wrote:
> > > > On Fri, Feb 22, 2019 at 04:32:27PM +0100, Erik Skultety wrote:
> > > > > Unfortunately, in order to support the new flags, the last patch introduces an
> > > > > API breakage as the convention we use for the bindings is to also enforce types
> > > > > for flags.
> > > >
> > > > Yes, unfortunately this need to break ABI is fallout resulting from
> > > > my decision to make the Go bindings do stricter enum validation that
> > > > we have had at the C level.
> > >
> > > How would this affect the ABI? Both the old and the new enum have the same int
> > > value 0x01, with the only difference that you could have fed a few more enums
> > > into the API even though we documented that they were unsupported for that
> > > usage.
> >
> > Previously an application would have done
> >
> > 	dom.ManagedSaveGetXMLDesc(libvirt.DOMAIN_XML_SECURE)
> >
> > With your change pushed, this becomes a compile error
> >
> >    demo.go:20:27 cannot use DOMAIN_XML_SECURE (type DomainXMLFlags) as type DomainSaveImageXMLFlags in argument to dom.ManagedSaveGetXMLDesc
> >
> > because the DomainXMLFlags  enum type doesn't match the new
> > DomainSaveImageXMLFlags enum type.
> 
> Yes, but if it's a compile time error, it's static type checking, isn't that
> still API breakage? I'd understand if e.g. it was a public structure and the
> project we'd expand the structure or added padding where the type is still the
> same, so compilation is okay, but from binary POV it would not...

Oh, i missed that you wrote  'ABI' rather than 'API'.

ABI is probably ok unless function param types result in symbol
mangling like C++ does, but I've not checked that.

Regards,
Daniel
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