Silly Q about circular references

[ppmoore]

Hello,

I have a silly question about circular references in C (note: not C++):

typedef void ( *FSM ) ( CALL_CB* );

typedef struct _fsm_cb
{

FSM fsm_entry;

} FSM_CB;

typedef struct _call_cb
{

FSM_CB *fsm;

} CALL_CB;

int main()
{

CALL_CB* call_cb;

return 1;

}

This can't compile because FSM_CB is referencing CALL_CB and vice versa:

test.c:4: syntax error before '*' token

I know that C++ has a solution to this, by simply declaring the second class before the first:

class Second;
class First
{

Second* m_second;

};
class Second
{

First* m_first;

};

main ()
{

First* aFirst;
Second* aSecond;

}

Can anyone help?

Thanks,
Paul

[Prelude]

>I know that C++ has a solution to this, by simply declaring the second class before the first
C has the same solution.

[SKeane]

struct _call_cb;

typedef void ( *FSM ) ( struct _call_cb* );

typedef struct _fsm_cb
{

    FSM fsm_entry;

} FSM_CB;

typedef struct _call_cb
{

    FSM_CB *fsm;

} CALL_CB;

int main()
{

    CALL_CB* call_cb;

    return 1;

}

Possibly

[ppmoore]

I had tried that, still doesn't work:

struct _call_cb;

typedef void ( *FSM ) ( CALL_CB* );

...

test.c:3: syntax error before '*' token

Any other ideas?
Paul

[SKeane]

Try reading what I actually posted?

I've highlighted the bit you missed.

[ppmoore]

Oops, thanks SKeane.

That worked! Great!
Paul

[SKeane]

Not saying it'll work mind!

[dwks]

You could also put the typedef beforehand (at least I think so, and Dinkumware does too):

typedef struct _call_cb CALL_CB;

typedef void ( *FSM ) ( CALL_CB* );

typedef struct _fsm_cb
{

    FSM fsm_entry;

} FSM_CB;

struct _call_cb
{

    FSM_CB *fsm;

};

int main()
{

    CALL_CB* call_cb;

    return 1;

}

[CornedBee]

Yes, that's valid. I would have posted it, but I was too lazy.