This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 110b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
[Voted into WP at the October, 2006 meeting.]
The following translation unit appears to be well-formed.
int x[true?throw 4:5];
According to 7.7 [expr.const], this appears to be an integral constant expression: it is a conditional expression, involves only literals, and no assignment, increment, decrement, function-call, or comma operators. However, if this is well-formed, the standard gives no meaning to this declaration, since the array bound (18.104.22.168 [dcl.array] paragraph 1) cannot be computed.
I believe the defect is that throw expressions should also be banned from constant expressions.
Notes from October 2002 meeting:
We should also check on new and delete.
Notes from the April, 2005 meeting:
Although it could be argued that all three of these operators potentially involve function calls — throw to std::terminate, new and delete to the corresponding allocation and deallocation functions — and thus would already be excluded from constant expressions, this reasoning was considered to be too subtle to allow closing the issue with no change. A modification that explicitly clarifies the status of these operators will be drafted.
Proposed resolution (October, 2005):
Change the last sentence of 7.7 [expr.const] as indicated:
In particular, except in sizeof expressions, functions, class objects, pointers, or references shall not be used, and assignment, increment, decrement,
function-call, orcomma operators shall not be used.
Note: this sentence is also changed by the resolution of issue 530.