Re: [Xen-devel] [PATCH] pci-attach: fix assertation

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Ian Campbell writes ("Re: [PATCH] pci-attach: fix assertation"):
> Ian, tools/libxl/libxl_internal.h says to initialised the transaction to 0
> rather than XBT_NULL explicitly -- I don't think there is a specific reason
> for that though?

It says:

/* Transaction functions, best used together.
 * The caller should initialise *t to 0 (XBT_NULL) before calling start.

I think that amounts to a promise that XBT_NULL == 0.  Therefore the
caller may (from a correctness pov) use either.

It is important that initialisation with 0 is supported because then
FILLZERO is known to DTRT.  (Note that, analogously, we are already
assuming that FILLZERO generates null pointers.)

I know that some people have strong views that writing NULL for null
pointers, rather than 0, is better.  I think it is needless verbiage.
A similar argument applies to XBT_NULL.  I think this is a bikeshed
and am happy to let it be whatever colour it comes from the factory
:-).

Ian.

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