Assuming the following C code:

struct Point {int x; int y;}; struct PointEx {int x; int y; int z;};

PointEx* getPointEx(); int length(Point*);

And its Scheme-interface:

(c-define-type Point "Point") (c-define-type Point* (pointer Point)) (c-define-type PointEx "PointEx") (c-define-type PointEx* (pointer PointEx))

(define get-PointEx (c-lambda () PointEx* "getPointEx")) (define Point-length (c-lambda (Point*) int "length"))

How do you use type tags properly? Doing (c-define-type PointEx* (pointer PointEx Point*)) still generates a warning in the case below. How do you write these so the C macro casts into Point* and not PointEx*?

(Point-length (get-PointEx))

The workaround is to write: (define Point-length (c-lambda (Point*) int "___result = length((Point*)___arg1);")) but I still want to clarify my understanding of tags and release functions.

BTW, I get many more warnings. I think it is because "int(x) = 3;" isn't a correct lvalue anymore. It does work because "int" is POD, but in fact this is a constructor call for any non-POD.