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Re: [Xen-devel] Returning errno values inside of hypercall structs (was: Re: [PATCH for-4.7 3/4] tools/xsplice: fix mixing system)

> > > IMHO, the best way to solve this is to define a set of XSPLICE_ERROR_* 
> > > that 
> > > covers the error codes returned by xsplice, and use that instead of XEN_* 
> > > errno values. This would make it much more easier to avoid mistakes when 
> > > coding the toolstack part of xsplice.
> > 
> > But why?
> > 
> > I must be missing something here - but the return from the hypercall
> > can return say 0 but the status->rc can be -XEN_EAGAIN.
> > 
> > Why does it need to be XSPLICE_ERROR_?
> Because nobody uses or enforces the correct usage of XEN_E* in the tools, so 
> people just use native error codes, which works on Linux, but breaks on 
> other OSes.

That was an oversigh on my part. I think changing the error code handling
in xen-xsplice to look for XEN_EXX is the right way.

But are you saying the BSD does not enforce the POSIX errors? errno.h is POSIX 

> Using something like XSPLICE_ERROR_* prevents people from having the bad 
> habit of directly using native OS error codes, by making it more obvious 
> that the error code is in a different space.

> Roger.

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