$function

The Xc++ language allows for reflecting free functions using $function.

For example the following is a $function declaration and typically appears in a public header:

// Function declaration in public header
$function+ void f();

The following is a $function definition and typically appears in a cpp file:

// Function definition in cpp file
$function+ void f()
{
}

The + is called the public modifier and means that the free function is public - so it is reflected and exported by the library.

Normally a $function in a public header of a library will use the public modifier, therefore Xcpp generates a warning if a $function is declared in a public header without the +.

When a $function is reflected an instance of a ReflectedGlobalFunction is registered in the ReflectedGlobalFunction registry.

The reflection information is sufficient to allow the cxPython library to call a registered $function from python.

Extern functions

<<extern>> allows a $function to be reflected and registered even though it is implemented in another library.

In that case there will be a $function declaration using <<extern>>, but there will be no $function definition (i.e. with a function body).

$function+ <<extern>> TcpMsgServer* CreateTcpMsgServer(
    IoContextPool* pool,
    EProtocol protocol,
    int32 port,
    bool reuse_addr, 
    ITcpMsgEndPoint& ep,
    const TcpMsgSessionSettings& sessionSettings);

For example this is needed for the free functions CreateIoContextPool(), CreateTcpMsgServer() and CreateTcpMsgClient() which are implemented in the cxMessage2 library which is not an xcpp project.

Inline functions

Inlined $functions are supported. Typically an inlined function appears in a public header of a library. It both declares and defines the function. It is reflected and registered in the normal way, however it is available as an inlined free function in C++.

The following is an example which appears in the ceda-core header IPersistable.h

$function+ inline OID GetOid(ptr<const IPersistable> po) 
{ 
    return po->GetPersistObjState().m_oid; 
}

Default parameters

A $function declaration supports default parameters. For example the following appears in the ceda-core header IPersistStore.h

$function+ PSpace* OpenPSpace(
    PersistStore* ps, 
    ConstStringZ name, 
    EOpenMode openMode = OM_OPEN_ALWAYS, 
    CSpace* cspace = nullptr);