[libvirt] [PATCH] fix WIN64 compatibility bug in external EventImpl API

[Daniel P. Berrange]

On Wed, Nov 19, 2008 at 01:28:23PM -0500, David Lively wrote:
> On Wed, 2008-11-19 at 16:49 +0000, Daniel P. Berrange wrote:
> > On Wed, Nov 19, 2008 at 11:41:43AM -0500, David Lively wrote:
> > > While starting to think about Windows compability, I realized the newly
> > > exposed API for registering an external EventImpl is not adequate.
> > > Currently it's assuming 32-bit unix fds.  But Windows uses a pointer
> > > (HANDLE) here.  So we need to generalize this interface so it can be
> > > implemented for 64-bit Windows.  The attached patch does this.  (I'm
> > > sure it conflicts with work Dan B is doing, so I'm hoping he'll just
> > > incorporate this into his changes.)
> > 
> > I'm not sure whether this is actually required. We're using gnulib for
> > socket stuff, and that wraps the Winsock socket() call so that it returns
> > a real file descriptor rather than a socket handle. It does this calling
> > _open_osfhandle which appears to be declared to accept a 'long' and return
> > an 'int' - at least in MinGW headers.
> 
> That means that the Windows application using libvirt must use gnulib as
> well.  If the Windows version of libvirt actually exports the gnulib
> bindings and headers, then I guess that's not a problem.  But does it
> export gnulib?

No, the gnulib stuff is internal only - we don't force any apps to also
use gnulib.

It does however mean we should document that the 'fd' arg of the
the  virEventAddHandle callback is an file handle, and not a socket
handle on Win32, so apps are clear on what to expect.

If they're not using gnulib themselves, they can trivially convert
back to a true socket handle if desired.

Daniel
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