[Libosinfo] [PATCH 6/8] list: Fix replacement in osinfo_list_add

[Christophe Fergeau]

Hi,

On Thu, Nov 05, 2015 at 04:59:20PM +0000, Daniel P. Berrange wrote:
> 
> This makes sense purely from the POV of correctness of the API, but
> I think there is another bug hiding here somewhere, because we AFAIR
> we should never get in a situation where we are replacing an existing
> entity in the list. When loading entities from the XML, we always
> check to see if the entity already exists, and if so re-use it rather
> than creating a new one. IOW, while this fix is valid, fixing it is
> masking what I think might be a more serious flaw elsewhere, that I
> would see to identify.

I ran a few more tests (added an assert in osinfo_list_add() if the
entity is already present in the list), and it turns out this happens
precisely because we reuse OS entities from the XML. We reuse what I'd
call 'top-level' entities, but we do not attempt to reuse entities used
to represent <media> nodes, or <tree> nodes, ... when we are parsing an
OS entity. So when we encounter a duplicate OS entity, we try to reuse
the existing one, and this entity has duplicates for the media/tree/...
we are trying to add, which triggers this misbehaviour.
The full list of entities which were duplicate are:
- OsinfoMedia
- OsinfoDeviceDriver
- OsinfoTree
- OsinfoOsVariant
- OsinfoInstallScript

Looking at the loading code for install scripts, there might be a bug
there as it may not be trying to reuse pre-existing entities.

Christophe
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