C++ :: Ioquake3 Engine - Accessing Limited Struct Fields

I'm currently working on the ioquake3 engine . The ioquake3 engine is separated into 2 different main threads at runtime: the gamecode and the engine. Both are communicating but not all information and my problem resides here.

In the gamecode, there's a struct called gentity_t which contains a lot of fields:

Code:
typedef struct gentity_s gentity_t;
struct gentity_s {
entityState_ts;// communicated by server to clients
entityShared_tr;// shared by both the server system and game
// DO NOT MODIFY ANYTHING ABOVE THIS, THE SERVER
// EXPECTS THE FIELDS IN THAT ORDER!
//================================
struct gclient_s*client;// NULL if not a client

[Code] ....

This whole entity is passed to the engine at runtime, but only the first two fields are declared for the engine:

Code:
// the server looks at a sharedEntity, which is the start of the game's gentity_t structure
typedef struct {
entityState_ts;// communicated by server to clients
entityShared_tr;// shared by both the server system and game
} sharedEntity_t;

My problem is that I need to access the health field of gentity_t from the engine. Technically, this is possible, but the health field is not declared in sharedEntity (which is the same memory address than gentity_t in the gamecode), so this is not straightforward.

I am looking for an elegant way to do this, and my constraint is that I must not edit the gamecode, only the engine.

The solutions I've thought:

- Just copy the whole gentity_t fields into sharedEntity_t. This would work I think but would be redundant, and I would like to avoid copying this huge set of fields.

- Include the two headers files declaring the gentity_t and sharedEntity_t structs, and create a Getter and a Setter functions that would cast a gentity_t over a sharedEntity_t and return/set a field. The problem is that I can't simply include them because they are both including some common headers files and this produce a recursive include error (and I can't modify the files to add a check, these are normally in the gamecode).

- Directly access the health field using a clever memory pointer, but I don't even know if that's possible given the huge number of fields prior health with many different types?