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.
Currently function types with different language linkage are not compatible, and 22.214.171.124 [expr.call] paragraph 1 makes it undefined behavior to call a function via a type with a different language linkage. These features are generally not enforced by most current implementations (although some do) between functions with C and C++ language linkage. Should these restrictions be relaxed, perhaps as conditionally-supported behavior?
Rationale (October, 2012):
CWG felt that this language design question would be better considered by EWG.
Any changes in this area should be pursued via a paper to EWG.