This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 112c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.
The following example ought to be well-formed, but the standard is insufficiently clear:
#define X <ciso646> ) #if __has_include( X && ( defined(X) ) #endif
Also, there is insufficient prohibition for the formation of __has_include by token pasting when performing macro replacement for the controlling expression of a conditional inclusion.