Re: [Xen-devel] [PATCH 23/28] libxl: ocaml: allow device operations to be called asynchronously

[Rob Hoes <Rob.Hoes@xxxxxxxxxx>]

> libxl.h says:
>  * *ao_how does not need to remain valid after the initiating function
>  * returns. All other parameters must remain valid for the lifetime of
>  * the asynchronous operation, unless otherwise specified.
> 
> So the ao_how can just be a normal stack variable if you like. If you want to
> use NULL/non-NULL-ness to indicate Some/None then:
>       struct ao_how aoh_struct, *aoh = NULL;
>       if (async != Val_none)
>               aoh = &aoh_struct
> works I think or just
>       struct ao_how aoh = { .callback = async_callback, ... };
> 
>       ret = libxl_device_##type##_##op(CTX, Int_val(domid), &c_info,
>       \
>                                        async != Val_none ? &aoh : NULL would 
> do.
> 

Ok, that makes sense. I have changed it to the second option.

Cheers,
Rob
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