Named struct vs. type alias for an unnamed struct

Question

In C++, is it semantically equivalent to have a named struct

struct S { int x; };

vs. a type alias for an unnamed struct

using S = struct { int x; }

?

Are there any differences in using the first or second version of S or are those variants completely interchangeable? Or is it very likely that some compiler have issues with the second version?

Answer 1

The using keyword with that context was introduced in C++11 which means that older compilers that work with the C++98 standard will not be able to compile it.

You will also not be able to forward declare your struct.

As such, no they are not 100% equivalent; but in some cases the using could be substituted for the usual declaration.