Re: [Xen-devel] [PATCH v6 1/4] xen: introduce SYMBOL

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.02.19 at 19:52, <dunlapg@xxxxxxxxx> wrote:

I'm not going to reply in detail to all of what you wrote about fanatics,
but I would like to say that I think compiler people less of that than
you appear to imply, at least the ones I know. In particular, they can
be convinced of there being bugs by pointing out what aspect of the
standard their implementation violates. (Of course there are also
going to be areas where interpretations of the standard vary too
much to come to an agreement.)

> Improvements this series seeks to make, as I understand it, include
> (in order of urgency):
> 
> 1. Fixing one concrete instance of "UB hazard"

Right, and we want to work around compiler bugs here.

> 2. Minimize risk of further "UB hazard" in this bit of functionality
> 3. Retain the effort Stefano has put in identifying all the places
> where such UB hazards need to be addressed.
> 4. Move towards MISRA-C compliance.
> 
> As far as I can tell, primary objections you've leveled at the options
> which try to address 2-4 are:
> 
> a. "UB hazard" still not zero
> b. MISRA compliancy no 100%
> c. Ugly
> d. Inefficient
> 
> (Obviously some proposals have had more technical discussion.)
> 
> Anything I missed?

I don't think so, especially since various aspects can fall under "ugly"
and/or "inefficient". What I'm not sure I see is what you mean to
express with all you wrote in terms of finding a way out of the
current situation (besides requesting a vote): Improving on a. and
b. is not a good excuse to extend c., at least not unequivocally.
Whether d. actually matters is a separate aspect, partly because it
may mean different things (it could e.g. be taken as another
wording for a. and b.).

And btw - I can't judge on b. anyway, as I still don't know what
exactly MISRA compliance is to mean, with the rules to adhere to
suitably justified.

Jan



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