FGMPRawSig

FGMPRawSig

The one callback shape every backend normalises to.

Declared in Plugins/GMP/Source/GMP/GMP/GMPHub.h:31

using FGMPRawSig = TGMPFunction<void(const FGMPTypedAddr*, const FGMPExtra*)>;

The C++ face and the actual ABI are not the same shape

FGMPRawSig is the type you name in C++. What actually crosses the boundary, after TGMPFunction erases it, is a three-argument bare function pointer:

void (*)(void* Self, const FGMPTypedAddr* Params, const FGMPExtra* Extra);

Parameter	What it is
Self	the callable's own address — not a UObject, not a vtable pointer
Params	array of Extra->Size erased arguments — see FGMPTypedAddr
Extra	the dispatch context — see FGMPExtra

Because Self is the callable rather than an object with a vtable, the call is an indirect jump and not a virtual dispatch.

Why one shape for everything

C++, Blueprint and all five scripting languages reach the core through this signature. Adding a language means implementing this single entry point and translating (Params, Extra) into that language's values — not writing a marshalling layer per language.

Backend	What it does with (Params, Extra)
UnLua / slua	push onto the lua stack
Puerts	convert to v8 values
AngelScript	fill AngelScript arguments
C#	pass straight through to an [UnmanagedCallersOnly] entry

The C# variant

C# registers a bare function pointer of its own shape:

using FGMPOnFireFn = void (*)(int64 /*cbHandle*/, const FGMPTypedAddr* /*paddrs*/, int32 /*numArgs*/);

Structurally the same idea — context first, then arguments — with the context being a managed delegate id rather than a void* Self. Native never dereferences it; it is handed back untouched. No reflection and no marshalling on that path.

In Shipping

With GMP_WITH_TYPENAME off, FGMPTypedAddr is layout-identical to uint64, so Params is literally an array of addresses. Type information, if needed, comes from Extra->TypeNames and Extra->Size.

See also

TGMPFunction · FGMPTypedAddr · FGMPExtra · Transparent rewrite