This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
[Voted into WP at October, 2009 meeting.]
There is no reason for the prohibition of using sizeof on “an enumeration type before all its enumerators have been declared” (18.104.22.168 [expr.sizeof] paragraph 1) if the underlying type of the enumeration is fixed.
Proposed resolution (July, 2009):
Change 22.214.171.124 [expr.sizeof] paragraph 1 as follows:
...The sizeof operator shall not be applied to an expression that has function or incomplete type, or to an enumeration type before all its enumerators have been declared, or to the parenthesized name of such types, or to an lvalue that designates a bit-field...