Question: I can't figure out what the actual problem is with this. 

```
typedef struct _actor
{
   ...
} _actor, Actor;

class Actor
{
   ...
};

```

I get this weird error message `actor.cpp:31: error: using typedef-name ‘Actor’ after ‘class’`. 

Any idea what I did wrong here? Thank you :)

Answer: 
You are not allowed to define the symbol `Actor` more than once. The `typedef` statement already defines the symbol `Actor` as an alias for `struct _actor` before you attempt to declare a class with the same name.

I'm guessing you're using the `gcc` compiler. I get the following errors when I compile with `gcc`:

```
../src/main.cpp:113: error: using typedef-name ‘Actor’ after ‘class’
../src/main.cpp:111: error: ‘Actor’ has a previous declaration here

```

The first message (pointing the `class Actor` line in the program) states that you cannot declare a class with a `typedef-name` (`Actor` is already declared using `typedef`). The second message (pointing to the `typedef struct _actor` line in the program) is a little clearer and refers to the multiple declarations for `Actor`.

It is very common in C/C++ for a single class of error like this to result in multiple compiler errors and often the more helpful message is not the first reported.
for arduino hectop 3d printer:

Rename `fpos_t` variables in `SdBaseFile.h` and `SdBaseFile.cpp` to another name like `fpos_t1` and recompile.