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.
[Moved to DR at the October, 2012 meeting.]
There does not appear to be wording that prohibits a block-scope extern object declaration from being a definition.
Proposed resolution (February, 2012):
Add the following as a new paragraph following 9.4 [dcl.init] paragraph 4:
[Note: Default arguments are more restricted; see 220.127.116.11 [dcl.fct.default].
The order of initialization of variables with static storage duration is described in 6.9.3 [basic.start] and 8.8 [stmt.dcl]. —end note]
To zero-initialize an object...