CVS difference for ais/ai-00216.txt

Differences between 1.6 and version 1.7
Log of other versions for file ais/ai-00216.txt

--- ais/ai-00216.txt	2002/02/05 02:06:24	1.6
+++ ais/ai-00216.txt	2002/02/07 04:56:41	1.7
@@ -674,4 +674,62 @@
 
 *************************************************************
 
+From: Randy Brukardt
+Sent: Monday, February  4, 2002 at  8:22 PM
+
+> 9) If a mechanism is introduced for reinstating suppressed checks
+>    (see AI-224), it must be made clear that the check suppression
+>    implied by an Unchecked_Union pragma is irrevocable.
+
+I'm not suppressing of checks is the right model here. An implementation is
+allowed to ignore check suppression anytime it wants. I'm not sure that an
+implementation could do any useful checking, but it seems like the model ought
+to be that there are no checks. That might be harder to define, though.
+
+*************************************************************
+
+From: Steve Baird
+Sent: Tuesday, February  5, 2002 at  6:01 PM
+
+I believe that suppression is the right model. An implementation
+is allowed to ignore check suppression in the case of an unchecked_union
+type. If an implementation is able to gather enough information from
+somewhere (certainly not from the zero-sized discriminant fields) to
+perform a check, it may do so.
+
+What is new about this form of suppression is that ignoring it
+is, in general, much harder (i.e. effectively impossible) than ignoring
+the suppression of other checks.
+
+I readily concede that the notion of a discriminant which exists in some
+theoretical sense (e.g. its value may be inferred in some cases)
+but occupies no storage is a bit odd.
+
+To me, the compelling advantage of this approach is its simplicity; only
+one line of RM text is needed because it uses an existing
+language mechanism.
+
+Inventing a similar-but-different set of rules expressly for
+Unchecked_Union would be much more complicated.
+
+*************************************************************
+
+From: Randy Brukardt
+Sent: Wednesday, February  6, 2002 at  6:05 PM
+
+> To me, the compelling advantage of this approach is its simplicity; only
+> one line of RM text is needed because it uses an existing language mechanism.
+
+Except that it messes up Unsuppress further; as the one with that short straw,
+I'm not amused :-)
+
+*************************************************************
+
+From: Robert Dewar
+Sent: Wednesday, February  6, 2002 at  7:30 PM
+
+You just say that Unsuppress unsupresses checks previously suppressed by
+Suppress, then that does not include the unchecked union stuff.
+
+*************************************************************
 

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