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Re: [libvirt] [PATCH] virsh: Correctly initialize libvirt



On Mon, May 09, 2011 at 04:04:41PM +0200, Matthias Bolte wrote:
> 2011/5/9 Jiri Denemark <jdenemar redhat com>:
> > virsh didn't call virInitialize(), which (among other things)
> > initializes virLastErr thread local variable. As a result of that, virsh
> > could just segfault in virEventRegisterDefaultImpl() since that is the
> > first call that touches (resets) virLastErr.
> >
> > I have no idea what lucky coincidence made this bug visible but I was
> > able to reproduce it in 100% cases but only in one specific environment
> > which included building in sandbox.
> 
> Well, actually all public API that can be called as the first public
> API function ever called in a sound program calls virInitialize first
> internally. For example virConnectOpen. The documentation of
> virInitialize suggest to call it first, but doesn't require it.
> 
> A fix in line with the current behavior would be to make
> virEventRegisterDefaultImpl and virEventRunDefaultImpl call
> virInitialize first too.

Yep that's good.

> 
> But this doesn't fix another problem, a program could call
> virDomainFree(NULL) for some reason as the first public API call ever
> made in the process and libvirt would try to report an error but would
> segfault because of calling virResetLastError before virInitialize was
> called.

IMHO that would be a mis-use of the API because they should call
virInitialize.

> So you found a much bigger problem and I'm not sure about the correct
> general solution. We could make calling virInitialize first mandatory
> but that might break existing applications. Or we make all public API
> functions call virInitialize first.

I think we could just clarify the docs

  "Calling virInitialize is mandatory, unless your
   first API call is one of

     virConnectOpen*
     virEventRegisterDefaultImpl"


Daniel
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