[LLVMdev] C as used/implemented in practice: analysis of responses

[David Keaton]

On 07/02/2015 05:30 PM, Philip Reames wrote:
>
>
> On 07/02/2015 04:44 PM, David Keaton wrote:
>> On 07/02/2015 03:17 AM, Kuperstein, Michael M wrote:
>>> You want to redefine ["won't break the program"], by specifying a new
>>> abstract machine, which is
>>> more conservative than standard C/C++. The proper way to do that would,
>>> I believe, be to work towards setting up a working group within the
>>> relevant committees, and come up with a uniformly accepted definition
>>> for this abstract machine, which could then be implemented (assuming
>>> there is, indeed, wide enough agreement in the implementer community –
>>> something that does not look at all likely) by next-generation
>>> compilers.
>>
>>      This work has already been done in Annex L of the C standard,
>> which provides an optional stricter abstract machine.  As far as I
>> know, no implementations have attempted to support Annex L yet.
> Do you have a link to the relevant text?  I've never heard of this, and
> a quick google search doesn't turn up anything relevant. Wikipedia knows
> about a set of "analyzability features", but that doesn't sounds like
> what you're talking about?

      The relevant text is inside the standard, which is for sale.  The 
cheapest source I know about is this.

http://webstore.ansi.org/RecordDetail.aspx?sku=INCITS%2fISO%2fIEC+9899%3a2011%5b2012%5d

      The title of Annex L is Analyzability, because that was the 
purpose, but the effect was to define a stricter abstract machine in 
which there were no unbounded undefined behaviors except what was 
absolutely necessary.  That does not address every question in the 
questionnaire, but it is a good start, and it has already been 
standardized so there is something concrete to implement.

					David