Re: [PATCH] libxl: new xlu_disk_parse function

[Ian Campbell <Ian.Campbell@citrix.com>]

On Thu, 2011-03-31 at 18:30 +0100, Ian Jackson wrote:
> Gianni Tedesco writes ("Re: [Xen-devel] [PATCH] libxl: new xlu_disk_parse function"):
> > On Thu, 2011-03-24 at 17:49 +0000, Ian Jackson wrote:
> > > +       return;
> > 
> >        case 1: ??
> 
> Deliberately omitted.
> 
> > > +    case 2:
> > > +    case 3:
> > > +    case 4:
> > > +       break;
> > 
> > Or does it belong here? In which case aborting on a parse error is bad
> > juju.
> >        case 1:
> > > +    default:
> > > +       abort();
> 
> I could add it there for clarity.  The regexp will always match
> capturing with 2, 3 or 4 parens.  None of the other errors from
> dfa_exec are applicable.  So anything other than 2,3,4 or "did not
> match" is due to a bug in the code, not merely bogus input.  Perhaps
> this should be mentioned in a comment.

I think that's a good idea, you'll only up nacking an endless stream of
fixup patches otherwise (inevitably adding the case in the wrong
place...).

IMHO a switch statement in this context obfuscates the error handling
and a couple of error handling if statements would be more obvious e.g.

	if (rc == PCRE_ERROR_NOMATCH) {
		xlu__disk_err(dpc, "bad syntax for target, or missing vdev");
		return;
	}

	/* The regexp will always match capturing with 2, 3 or 4 parens */
	if (rc < 2 || rc > 4)
		abort();

	.. carry on...