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Re: [Libvir] PATCH: Make the virBuffer API harder to misuse



On Mon, Apr 28, 2008 at 03:17:33AM -0400, Daniel Veillard wrote:
> On Sat, Apr 26, 2008 at 05:37:11PM +0100, Daniel P. Berrange wrote:
> > 
> > 
> > The following set of changes adjust the way errors are handled in the
> > virBuffer routines. The key idea is to make it hard (impossible) to
> > misuse the API, with each change addressing one of the errors scenarios
> > I've found in existing code using the routines.
> 
>   In general I agree an like the change, except
> 
> >  - The contents of the struct are no longer public.
> > 
> >    Rationale: This stops people accessing the buffer directly,
> >    thus preventing use of data which may be in an error state.
> 
>  results in this:
> >  struct _virBuffer {
> > -    char *content;          /* The buffer content UTF8 */
> > -    unsigned int use;       /* The buffer size used */
> > -    unsigned int size;      /* The buffer size */
> > +    char *padding[__SIZEOF_VIR_BUFFER]; /* This struct contents is private */
> >  };
> 
>   which is really not nice. 
> I would prefer to relax the 'non-public' point and let the compiler 
> compute the size in some ways rather than hardcode based on a word size
> indication which may not take into account specific alignment problems
> on some platforms.

One other option I considered is to just define the struct in the public 
header with meaningless field names

  struct _virBuffer {
     char a;
     unsigned int b;
     unsinged int c;
  };

The real version is re-declared with proper names in buf.c, so this will
at least discourage its use which is probably good enough.

Dan.
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