Cyclic header dependency

[pallav]

I have to header files, circuit.h and latch.h that reference each
other and are causing a cyclic dependency.

latch.h file

#include "circuit.h"
typedef boost::shared_ptr<struct Latch> LatchPtr;

class Latch
{
...
CircuitPtr circuit;
};

circuit.h file

#include "latch.h"
typedef boost::shared_ptr<struct Circuit> CircuitPtr;

class Circuit
{
...
list<LatchPtr> latches;
};

As you can see there is a cyclic dependency. To get things to compile,
what I've done is
I've changed the circuit.h file as follows:

new circuit.h file

// defined in latch.h, can't do #include "latch.h" as that will
introduce cyclic dependency
extern typedef boost::shared_ptr<struct Latch> LatchPtr;

typedef boost::shared_ptr<struct Circuit> CircuitPtr;

class Circuit
{
...
list<LatchPtr> latches;
};

This solves the problem, but I'm wondering if this is the way to fix
such issues. I know C++ has forward declarations but I"m still trying
to figure out how to use them and if they'll solve this. The other
option is to combine the two header files but I would prefer not to do
that.

Is the above fix bad practice? thanks for your time.

 

[anon]

I have to header files, circuit.h and latch.h that reference each
other and are causing a cyclic dependency.

latch.h file

#include "circuit.h"
typedef boost::shared_ptr<struct Latch> LatchPtr;

class Latch
{
...
CircuitPtr circuit;
};

circuit.h file

#include "latch.h"
typedef boost::shared_ptr<struct Circuit> CircuitPtr;

class Circuit
{
...
list<LatchPtr> latches;
};

As you can see there is a cyclic dependency. To get things to compile,
what I've done is
I've changed the circuit.h file as follows:

new circuit.h file

// defined in latch.h, can't do #include "latch.h" as that will
introduce cyclic dependency
extern typedef boost::shared_ptr<struct Latch> LatchPtr;

typedef boost::shared_ptr<struct Circuit> CircuitPtr;

class Circuit
{
...
list<LatchPtr> latches;
};

This solves the problem, but I'm wondering if this is the way to fix
such issues. I know C++ has forward declarations but I"m still trying
to figure out how to use them and if they'll solve this. The other
option is to combine the two header files but I would prefer not to do
that.

Is the above fix bad practice? thanks for your time.

1) declare in the header file - implement (define) in the source file
2) if you really want to do like you did, then do this:
In circuit.h, do not include latch.h, but declare Latch class:

class Latch;
typedef boost::shared_ptr<class Latch> LatchPtr;

class Circuit
{
...
list<LatchPtr> latches;
};


BTW you had an error in your typedef