Why package a single enum in a struct?

Question

This is written by someone who has left the company. I can't see any reason to do this and am curious if there's something I am missing.

enum thing_type_e
{
   OPTION_A = 0,
   OPTION_B,
   OPTION_C,
   OPTION_D
};

struct thing_type_data_s
{
   enum_type_e mVariable;
};

I supposed it's possible he was going to add more to the structure, but after looking at how it is used, I don't think so.

Barring "he was going to add more to the structure," why package a single enum in a struct? Is there some motivation I'm not thinking of?

Update:

As asked in the comments, he used it in this fashion:

void process_thing_type(thing_type_data_s* ParamVariable)
{
    local_variable = ParamVariable->mVariable;
    ...
}

This was originally built with GCC 3.3.5 if it makes any difference.

Answer 1

Possibly to enforce some type safety. Old-style enums are implicitly convertible to integral types, and this is not always desirable. Besides this, they are unscoped.

C++11 adds scoped enumerations (or "class" enums) to fix both of these issues.

Here's an example:

void foo(int) {}

int main()
{
  foo(OPTION_A);  // OK
  thing_type_data_s s = { OPTION_A };
  foo(s);  // Error
}