Semantics of p_c_pointer and PointerToCPtr

[certik]

Currently p_c_pointer(pointer(xi32), p) gets translated to:

         (= 
            (Var 6 p) 
            (PointerToCPtr 
               (GetPointer 
                  (Var 6 xi32) 
                  (Pointer 
                     (Integer 4 [])) ()) 
               (CPtr) ()) ()) 

and p_c_pointer(xi64, p) gets translated to:

         (= 
            (Var 6 p) 
            (PointerToCPtr 
               (Var 6 xi64) 
               (CPtr) ()) ()) 

What should be the recommended usage? It seems to me the second case is incorrect, as PointerToCPtr should only accepts pointers as the first argument?

The other issue is: we need to also have a CPython implementation of whatever syntax/semantics we choose. If it cannot be done for the above syntax, then we need to change it.

[czgdp1807]

We can use ctypes to run the code with CPython?

[certik]

Yes, we already do in ltypes.py.

[czgdp1807]

I see. So just importing stuff from ctypes into ltypes will allow CPython to at least run the code. However, I am wondering can CPython really call into C code. Like AFAIK, LPython generates an object file and that's linked to the object file of .c file (where we implement the C functions called in Python code). Now since CPython never generates an object file then how will the C functions linked to their definition.

[certik]

Yes, so callbacks cannot be done from CPython, I also just realized that, so we will simply not implement @ccallable in CPython. But calling into C is possible, and it works already. So all other features we'll get working.