Function pointers

Global Pointer

Test()
CallFunction( Pointer ) ;<--- This is the C function that calls the Blitz function by it's pointer
WaitKey()
End

Function Test()
	Pointer = FunctionPointer() ;<--- This is the C function that returns the function pointer
	
	Print "This works! Function pointer: " + Pointer

	Return  ;<--- This works fine when the function is called by Blitz
	;however, when the DLL calls this function, 'Return' leads to a MAV
End Function

Global Pointer, Call

Print Test()
CallFunction( Pointer )
WaitKey()
End

Function Test()
	Pointer = FunctionPointer()
	
	Print "Works! Call no. " + Call
	
	Call = Call + 1
	
	If Call = 1 Then
		Return 5
	Else
		ReturnInt( 5 )
	EndIf
End Function

#define BBEXPORT extern "C" _declspec(dllexport)

void (__stdcall *JumpFunction)(void);

BBEXPORT int __stdcall FunctionPointer() {
	unsigned int StackPosition, Adress;

	__asm {
		mov StackPosition,esp
		mov esp,ebp
		add esp,4
		pop Adress
		mov esp,StackPosition
	}

	return Adress - 8;
}

BBEXPORT int __stdcall CallFunction( int (__stdcall *B3DFunction)(void) ) {
	unsigned int StackPosition;

	__asm {
		mov StackPosition,esp
		mov esp,ebp
		add esp,4
		pop JumpFunction
		mov esp,StackPosition
	}

	return B3DFunction();
}

BBEXPORT void __stdcall ReturnInt( int Value ) {
	__asm {
		mov eax,[Value]
	}

	JumpFunction();
}

Global Pointer
GoSub Test

CallFunction( Pointer )
WaitKey()
End

.Test
	Pointer = FunctionPointer()
	Print "Hello, I am called from both Blitz and C!"
Return ;<---- With GoSub instead of Function, 'Return' works without a Memory Access Violation

Global Pointer, FirstCall = True
GoSub Test

CallFunction( Pointer )
WaitKey()
End

.Test
	Pointer = FunctionPointer()
	
	If FirstCall Then
		FirstCall = False
		Return
	Else
		B3DFunction()
	EndIf
Return

Function B3DFunction()
	StringVar$ = "This function can handle strings without a problem!"
	
	Print StringVar
End Function

'++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
' Pointeur de fonction / Gosub-Return
'++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
#COMPILER PBWIN 9
#COMPILE DLL
'
FUNCTION FunctionPointer ALIAS "FunctionPointer" () EXPORT AS LONG
    DIM StackPosition AS LONG
    DIM Adress AS LONG

      !  mov StackPosition,esp
      !  mov esp,ebp
      !  add esp,4
      !  pop Adress
      !  mov esp,StackPosition

    FUNCTION = Adress - 8
END FUNCTION

SUB GOSUB_EXTRN ALIAS "Gosub_Extrn" (BYVAL Adresse AS LONG PTR) EXPORT
    GOSUB DWORD Adresse
END SUB

.lib "BLITZ_FP.DLL"

FunctionPointer%()    : "FunctionPointer"
Gosub_Extrn(Adresse%) : "Gosub_Extrn"

Global V$      ; No Pb with string. works well in Debug or Release Mode
Global Pointer ; Init pointer
Gosub Test            ; Call From Blitz3D
Gosub_Extrn(Pointer) ; Call From/By the DLL
WaitKey()
End

.Test
	Pointer = FunctionPointer()
        v$="Pointer value is " + Pointer
	Print "Hello, I am called from both Blitz and C!"
        Print V$
Return 

'
FUNCTION FunctionPointer ALIAS "FunctionPointer" ()  AS UInteger Export
    DIM StackPosition AS UInteger
    DIM Adress AS UInteger
    Asm
      	mov [StackPosition],esp
      	mov esp,ebp
      	Add esp,4
      	pop [Adress]
      	mov esp,[StackPosition]
    End Asm
    Return Adress - 8
END FUNCTION

SUB GOSUB_EXTRN ALIAS "Gosub_Extrn" (BYVAL Adresse AS UInteger PTR) EXPORT
    Asm Call [Adresse]
END SUB

.lib "BLITZFB_FP.DLL"

FunctionPointer%()    : "FunctionPointer@0"
Gosub_Extrn(Adresse%) : "Gosub_Extrn@4"

FunctionPointer% ()
DataPointer% ()
LabelPointer% ()
ArrayPointer% ()
VarPointer% ()
TypePointer% (type*)

CallFunction% (FunctionPointer%)
CallFunctionVarInt% (FunctionPointer%, value%)
CallFunctionVarFloat% (FunctionPointer%, value#)
CallFunctionVarType% (FunctionPointer%, value*)

GotoPointer% (LabelPointer%)
GosubPointer% (LabelPointer%)

CreateThread% (FunctionPointer%, Value%)
FreeThread% (Thread%)
PriorityThread% (Thread%, Priority%)
PauseThread% (Thread%)
ResumeThread% (Thread%)
WaitThread% (Thread%, Timeout%)
IsThread% (Thread%)

...

MyFunctionFirstPointer = FunctionPointer()
	Goto skip
	MyFunctionFirst()
	.skip

MyFirstLabelPointer = LabelPointer()
	Goto skip
	Goto MyFirstLabel
	.skip

Blitz source

; Init The pointer. Do not change this structure
;++++++++++++++++++++++++++++++++++++
Pointer = GetPointer()
	Goto skip
	Goto Test
	.skip
;++++++++++++++++++++++++++++++++++++

While Not KeyDown(1)
	a=a+1
	Print "This is the main " + A
	Delay 100
	If a=30 Then Gosub_Ex pointer
Wend
End 

.Test
	Print "Hello, I am called from the DLL"
	For i=1 To 1000
		Delay 1
		Print ">>>> CALL BY THE DLL "+ i
    Next
Return 

#COMPILER PBWIN 9
#COMPILE DLL
'
FUNCTION GetPointer ALIAS "GetPointer" () EXPORT AS LONG
    DIM StackPosition AS LONG
    DIM Adress AS LONG

      !  mov StackPosition,esp
      !  mov esp,ebp
      !  add esp,4
      !  pop Adress
      !  mov esp,StackPosition

    FUNCTION = Adress + 8
END FUNCTION

SUB Gosub_Ex ALIAS "Gosub_Ex" (BYVAL Adresse AS LONG PTR) EXPORT
    GOSUB DWORD Adresse
END SUB

BBAEXPint CreateSampleMesh()
{
	int mesh = bb_CreateMesh(0);
	int surf = bb_CreateSurface(mesh,0);
	bb_AddVertex (surf, -1.0f,+1.0f,0.0f, 0.0f,0.0f,0.0f);
	bb_AddVertex (surf, +1.0f,+1.0f,0.0f, 1.0f,0.0f,0.0f);
	bb_AddVertex (surf, +0.0f,-1.0f,0.0f, 0.5f,1.0f,0.0f);
	bb_AddTriangle (surf,0,1,2);
	return mesh;
};

BBAEXPint CreateSampleMesh()
{
	int mesh = bb_CreateMesh(0);
	int surf = bb_CreateSurface(mesh,0);
	int a = bb_AddVertex (surf, -1.0f,+1.0f,0.0f, 0.0f,0.0f,0.0f);
	int b = bb_AddVertex (surf, +1.0f,+1.0f,0.0f, 1.0f,0.0f,0.0f);
	int c = bb_AddVertex (surf, +0.0f,-1.0f,0.0f, 0.5f,1.0f,0.0f);
	int t = bb_AddTriangle (surf,a,b,c);
	return mesh;
};