I don't understand. Libvirt users must of course compile API and application with the same libvirt.h, after updating the value of VIR_MAX_CPUS when necessary. And go from first info element to next one by (info+1), which adds sizeof(virVcpuInfo) to address, including correct length of cpumap according to:
unsigned char cpumap[(VIR_MAX_CPUS + 7) / 8]; /* Bit map of usable real CPUs.
For alignment constraints, compiler rounds up the sizeof(virVcpuInfo)when needed.

Veuillez répondre à veillard@redhat.com

Pour : michel.ponceau@bull.net
cc : libvir-list@redhat.com
Objet : Re: Proposal : add 3 functions to Libvirt API, for virtual CPUs

On Tue, Jul 11, 2006 at 05:29:52PM +0200, michel.ponceau@bull.net wrote:
> 2) CPU map cut into standard + extension : It would be more simple to let
> each Libvirt user modify the value of VIR_MAX_CPUS in private libvirt.h.
> It could be similar to the version number update, from libvirt.h.in to
> libvirt.h :
> #define LIBVIR_VERSION_NUMBER @LIBVIRT_VERSION_NUMBER@

No, I do think it is instead very hard. You start to get into very annoying
problems from an API point of view. How do you go from the first element
in the info array to the next one ? in the client it's already not nice,
you must do pointer arithmetic (and I really don't want to push an API which
forces that to most users), it expose potential serious problem like alignment
and packing, problems between versions of compilers and tools.
In a nutshell I don't want an API where one need to access an array of
structure where the size of the structure is not defined by the API itself.

What I suggested did that in both case, either low number of CPUs and
fixed size records like you initial solutions, or high number of CPUs and
you work on a two dimentional array of bytes.

Daniel

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