Struct in file.c

I think with C++ classes you only have access to its virtual methods.

To be able to use memory allocated in C via a BlitzMax Type, you need to do some trickery. And you cant use all BlitzMax types, such as Strings/Objects/Arrays etc.

And this may brake if there are changes to the way BlitzMax handles types.

This is just one way of doing it, there are probably more.

test.bmx:

Import "test.c"

Extern "C"
	Type TStruct
		Field I:Int
		Field F:Float
		Field S:Byte Ptr
	EndType
	
	Function CreateStruct( struct:TStruct Var, i:Int, f:Float, s$z)
	Function CreateStruct2:TStruct( i:Int, f:Float, s$z)
	Function FreeStruct( struct:TStruct Var)
EndExtern

'Local struct:TStruct = CreateStruct2( 10, 1.5, "Hello World!")
Local struct:TStruct
CreateStruct( struct, 10, 1.5, "Hello World!")
Print "ptr: " + Int(Byte Ptr struct)
Print "i: " + struct.i
Print "f: " + struct.f
Print "s: " + String.FromCString(struct.S)
FreeStruct( struct)
Print "ptr: " + Int(Byte Ptr struct)

test.c:

typedef struct {
	int i;
	float f;
	char* s;
} STRUCT;

void CreateStruct( STRUCT** out, int i, float f, char* s) {
	STRUCT* sc = (STRUCT*)malloc( sizeof( STRUCT));
	sc->i = i;
	sc->f = f;
	sc->s = s;
	*out = (char*)sc - 4; // this is the important part!
}

STRUCT* CreateStruct2( int i, float f, char* s) {
	STRUCT* sc = (STRUCT*)malloc( sizeof( STRUCT));
	sc->i = i;
	sc->f = f;
	sc->s = s;
	return (char*)sc - 4; // this is the important part!
}

void FreeStruct( STRUCT** sc) {
	if( (*sc)->s) free( (*sc)->s); // make sure we free the string, if any
	free( *sc);
	*sc = (void*)0;
}