[Xen-devel] Re: non-ANSI Unions

[PUCCETTI Armand <armand.puccetti@xxxxxx>]

Sorry, it was an err in the tool. Such unions are now understood properly.

Anthony Liguori a écrit :
> PUCCETTI Armand wrote:
> > Many "unions' are present in the code, but are non-ANSI!
> Anonymous unions/structs are a rather common C extension.  They are 
> much preferred to using a named union for the syntactical convenience 
> of writing:
> page_info.list
>
> vs writing:
>
> page_info.u.list
>
> Also, this is not the only C extension that Xen utilizes.  If your 
> analysis tool doesn't support the various GCC extensions, then it's 
> not going to be much help.
> Regards,
>
> Anthony Liguori
>
> > For instance, I see:
> >
> > struct page_info
> > {
> >    /* Each frame can be threaded onto a doubly-linked list. */
> >    union {
> >        struct list_head list;
> >        /* Shadow uses this field as an up-pointer in lower-level 
> > shadows */
> >        paddr_t up;
> >    };
> >    /* Reference count and various PGC_xxx flags and fields. */
> >    u32 count_info;
> > ...}
> >
> > which should be written properly:
> >
> > struct page_info
> > {
> >    /* Each frame can be threaded onto a doubly-linked list. */
> >    union {
> >        struct list_head list;
> >        /* Shadow uses this field as an up-pointer in lower-level 
> > shadows */
> >        paddr_t up;
> >    } foo;
> >
> >    /* Reference count and various PGC_xxx flags and fields. */
> >    u32 count_info;
> > ...}
> >
> > Is there any good reason to do so? Is it possible to change that, to 
> > comply with the standard
> > (and therefore with analysis tools too) ?
> >
> > Armand

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