For example, the following code is valid both in C++ 2011 and in
this revision of C++, but the macro invocation produces different outcomes
because the single quotes delimit a
character-literal in C++ 2011, whereas they are digit
separators in this revision of C++:
#define M(x, ...) __VA_ARGS__
int x[2] = { M(1'2,3'4, 5) };