🚀 go-pugleaf

In article <1992Dec30.075041.10907@sq.sq.com> msb@sq.sq.com (Mark Brader) writes:
+
+> #2)  GCC fails to detect the error in the following code, even when the
+>      -pedantic-errors option is used.
+> 
+> unsigned long overflow = LONG_MAX + 3; /* ERROR */
+
+I presume this is being called erroneous because of the constraint:
+
+#  Each constant expression shall evaluate to a constant that
+#  is in the range of representable values for its type.

Yes.

+in section 3.4 (ANSI) / 6.4 (ISO).  However, 3.4/6.4 also says:
+
+#  The semantic rules for evaluation of a constant expression
+#  are the same as for non-constant expressions.
+
+This presumably includes the assertion in 3.3/6.3:
+
+#  If an "exception" occurs during the evaluation of an expression
+#  (that is, if the result is not mathematically defined or not in
+#  the range of representable values for its type), the behavior
+#  is undefined.
+
+Since the constraint on the constant-expression applies to the *result*
+of evaluating it, but the undefined behavior due to overflow applies
+*during* the evaluation, I think "undefined behavior" wins.

Well, you're wrong.  x3j11 has already ruled on this exact issue. In
Technical Information Bulletin #1, request for interpretation #31
(and its response) make it quite clear that as fas as x3j11 is concerned,
the expression (LONG_MAX + 3), when appearing in a context requiring
a constant expression, is a constraint violation.  Interestingly enough,
it is also x3j11's interpretation (or so I have been led to believe)
that the expression (ULONG_MAX + 3) does *not* violate any constraint!
(But that's an entirely separate issue.)


// Ron ("Loose Cannon") Guilmette    uucp: ...uunet!lupine!segfault!rfg
//
//      "On the one hand I knew that programs could have a compelling
//       and deep logical beauty, on the other hand I was forced to
//       admit that most programs are presented in a way fit for
//       mechanical execution, but even if of any beauty at all,
//       totally unfit for human appreciation."
//                                              -- Edsger W. Dijkstra
-- 

// Ron ("Loose Cannon") Guilmette    uucp: ...uunet!lupine!segfault!rfg
//
//      "On the one hand I knew that programs could have a compelling
//       and deep logical beauty, on the other hand I was forced to
//       admit that most programs are presented in a way fit for
//       mechanical execution, but even if of any beauty at all,
//       totally unfit for human appreciation."
//                                              -- Edsger W. Dijkstra