This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 115d. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
2024-10-26
[Moved to DR at the October, 2012 meeting.]
According to 7.6.2.2 [expr.unary.op] paragraph 5,
The address of an object of incomplete type can be taken, but if the complete type of that object is a class type that declares operator&() as a member function, then the behavior is undefined (and no diagnostic is required).
This should actually be “ill-formed, no diagnostic required” instead of undefined behavior, since the problem could be detected by whole-program analysis. Also, it's not clear what this means for constant expressions.
Proposed resolution (February, 2012):
Change 7.6.2.2 [expr.unary.op] paragraph 5 as follows:
The address of an object of incomplete type can be taken, but if the complete type of that object is a class type that declares operator&() as a member function, then the behavior is undefined (and no diagnostic is required).If & is applied to an lvalue of incomplete class type and the complete type declares operator&(), it is unspecified whether the operator has the built-in meaning or the operator function is called. The operand of & shall not be a bit-field.