C++ is mostly a superset of C, but not always. In particular, while enumeration values in both C and C++ implicitly convert into int, the reverse isn't true: only in C do ints convert back into enumeration values. Thus, bitflags defined via enumeration declarations don't work correctly. Hence, this is OK in C, but not in C++:
typedef enum Foo
{
Foo_First = 1<<0,
Foo_Second = 1<<1,
} Foo;
int main(void)
{
Foo x = Foo_First | Foo_Second; // error in C++
return 0;
}
How should this problem be handled efficiently and correctly, ideally without harming the debugger-friendly nature of using Foo as the variable type (it decomposes into the component bitflags in watches etc.)?
Consider also that there may be hundreds of such flag enumerations, and many thousands of use-points. Ideally some kind of efficient operator overloading would do the trick, but it really ought to be efficient; the application I have in mind is compute-bound and has a reputation of being fast.
Clarification: I'm translating a large (>300K) C program into C++, so I'm looking for an efficient translation in both run-time and developer-time. Simply inserting casts in all the appropriate locations could take weeks.