When is a semicolon after } mandated in c/c++?

Question

if(...) {
  ...
}

It seems in the above case a ; is optional,when is a semicolon after } necessary in c/c++?

Answer 1

int a[2] = {1,2}, j = 5;

When initialization of array or structure are done with {} all the subsequent variables are declared after ,.

Edit: As you changed your question; ; is mandatory after the class, enum, initialization syntax declarations.

class A {};  // same for `struct
enum E {};   // enum class (c++0x)
int a[] = {1,2};  // array or object initialization

And as per comment by @rubenvb:

do {} while(condition);