Paul Schlie wrote: >> Joseph Myers wrote: >> DR#260 seems clear enough that indeterminate values may be treated >> distinctly from determinate values including randomly changing at any >> time. <http://www.open-std.org/jtc1/sc22/wg14/www/docs/dr_260.htm> > > One can only hope that the recommendations won't see the light of day in > their present form, as it's fairly clear that once an unspecified value is > read (presuming absents of a trap representation), it becomes logically > visible, and thereby clearly no longer logically indeterminate.
It's not "fairly clear" to me; in fact, it seems to ignore the specific definition of "indeterminate" which overrides any preconceived or more general notion of what the word might mean in other contexts. The only relevant definitions/meanings of "indeterminate" are those found in the standard and its corrigenda. > Further, regardless of the recommendations; and presuming absents of any > possibility of a trap representation for a given implementation; x ^= x > remains well defined, although not necessarily equivalent to 0; as although > lvalue x remains well defined, its rvalue is proposed to remain repetitively > unspecified until being assigned the result of the dynamically evaluated xor > operation having two potentially differing unspecified operand values. > > (as the undefined behavior referenced in the DR is related to a pointer > becoming indeterminate because it was assigned an indeterminate value, or > the object it had referenced has been freed and thereby no longer a valid > object of the pointer's type, and thereby although the pointer's value has > not changed, it's value is now considered a trap representation; not because > the value it references has been assigned an indeterminate value) No, that's just an example: the text makes it clear that this isn't an issue just about pointers. (The resolution of DR#260 covers a number of related points, which may cause this apparent lack of clarity.) Note that DR#260's resolution says "While an object holds an indeterminate value it is indeterminate. Successive reads from an object that is indeterminate might return different results." Nothing about pointers; this applies to all objects. -- James
