Re: As-if Infinitely Ranged Integer Model

["Joseph S. Myers" <joseph at codesourcery dot com>]

As further comments, it's unfortunate that this document has chosen 
certain badly thought out basis documents and concepts.

On page 13 you have a short table of "critical undefined behavior" and an 
attempt to define "bounded undefined behavior", that ignore all my 
previous comments in this area, especially the detailed list of cases I 
sent in reflector message 11499.  As I said there:

  First, there isn't a clear definition of what the bounds are; if you are 
  trying to bound possible behavior, I think it needs to be clear enough to 
  define a set of possible executions in the abstract machine.

If people want predictability across implementations, they must stop 
ignoring the issues and hoping that "undefined but not quite so undefined 
as all that" will magically solve their problems, and instead seriously 
put in the weeks or months of work in detailed analysis of every instance 
of undefined behavior and proper definitions in the abstract machine (that 
are actually implementable) to bound the possible executions; removing 
"undefined" does not introduce semantics that were never previously needed 
or agreed, only careful thought and drafting and textual review work in 
hundreds of individual cases can do so.  The definition in your document 
fully permits bounded undefined behavior to make daemons fly out of your 
nose, as that is not an out-of-bounds store.

Then you are building on the runtime-constraint mechanism and rsize_t of 
TR 24731-1.  TR 24731-1 is considered useless in the Linux world, and not 
implemented in the GNU C Library, and with good reason; see 
<http://sourceware.org/ml/libc-alpha/2007-09/msg00069.html>.  If you want 
general adoption in the Linux world you will need to extract those pieces 
from the pile of useless, duplicative and prior-art-ignoring functions 
that is most of TR 24731-1 and demonstrate that despite their background 
the runtime-constraints and rsize_t have more general utility.

-- 
Joseph S. Myers
joseph@codesourcery.com