Question

Possible Duplicate:
Is the typedef-name optional in a typedef declaration?

I’m on Visual Studio 2008 and I saw this:

typedef enum testfoo
{
    enum1,
    enum2,
    enum3
};

Normally the C-style way of using typedef this way requires one additional piece (the name):

typedef enum testfoo
{
    enum1,
    enum2,
    enum3
} testfoo_name;

What is the former example doing? Strangely it compiles, but not sure what it’s actually defining.

Answer 1

There is a difference. The second creates an alias for the enum but the first doesn’t. The typedef in the first example doesn’t actually do anything. This gives me a warning in GCC so I suspect you can take it out.

In C, it’s common to typedef structs and enums so as to avoid instantiating with the struct or enum name. For instance:

struct A {};

struct A a;

To shorten this, a typedef does the trick:

typedef struct {} A;

This is no longer necessary in C++ so I’m deriving my assumption of his misconception with this concept. Or maybe the author forgot to give it a name…

The same thing occurs when using classes or structs:

typedef struct A {}; // simply a class-declaration, generates a warning