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.
According to the grammar in 5.13.9 [lex.ext], a ud-suffix is an identifier. However, implementations seem to agree that "x"or"y" is equivalent to "xy"or and not to true. Should the Standard permit identifier-like alternative tokens as ud-suffixes?
Rationale (October, 2015):
The identifier in a ud-suffix is required to begin with an underscore, and the identifier-like alternative tokens do not satisfy this requirement.