[cpyrt] Use GetActualClass in cast_actual (#90)

cast_actual kept the static class, so comparing two proxies of the same
object through different base subobjects compared unequal addresses.
Reachable when a proxy is not downcast on creation, e.g. for a pinned
type. Also drops a stray '&' from the ostream operand name used for the
operator<< lookup, and fixes two comment typos.

Author: aaronj0

src/cpyrt/CPPInstance.cxx

@@ -281,7 +281,7 @@ static PyObject* op_destruct(CPPInstance* self) {
 
 //= cpyrt object dispatch support =========================================
 static PyObject* op_dispatch(PyObject* self, PyObject* args,
-                             PyObject* /* kdws */) {
+                             PyObject* /* kwds */) {
   // User-side __dispatch__ method to allow selection of a specific overloaded
   // method. The actual selection is in the __overload__() method of
   // CPPOverload.
@@ -554,8 +554,7 @@ static inline void* cast_actual(void* obj) {
     return address;
 
   interop::TCppScope_t klass = ((CPPClass*)Py_TYPE((PyObject*)obj))->fCppType;
-  interop::TCppScope_t clActual =
-      klass /* XXX: interop::GetActualClass(klass, address) */;
+  interop::TCppScope_t clActual = interop::GetActualClass(klass, address);
   if (clActual && clActual != klass) {
     intptr_t offset = interop::GetBaseOffset(
         clActual, klass, address, -1 /* down-cast */, true /* report errors */);
@@ -827,7 +826,7 @@ static PyObject* op_str(CPPInstance* self) {
         interop::TCppScope_t rnsID =
             interop::GetScope(TypeManip::extract_namespace(rcname));
         PyCallable* pyfunc =
-            Utility::FindBinaryOperator("std::ostream&", rcname, "<<", rnsID);
+            Utility::FindBinaryOperator("std::ostream", rcname, "<<", rnsID);
         if (!pyfunc)
           continue;
 

src/cpyrt/CPPMethod.cxx

@@ -297,7 +297,7 @@ void cpyrt::CPPMethod::SetPyError_(PyObject* msg) {
   //      C++ method to give some context.
   //   2. A C++ exception has occured:
   //      Augment the exception message with the docstring of this method
-  //   3. A Python exception has occured with a traceback:
+  //   3. A Python exception has occurred with a traceback:
   //      Do nothing, Python exceptions are already informative enough
   //   4. If the Python exception has no traceback hinting to an internally set
   //   error stack,

test/test_pythonify.py

@@ -617,3 +617,32 @@ def test03_write_access_to_globals(self):
         assert proxy.__get__(proxy, None) == 3
 
         cppjit.gbl.ns_example01.gMyGlobalInt = oldval
+
+
+class TestPINNEDCOMPARISON:
+    def test01_pinned_base_compares_equal(self):
+        """Comparison downcasts to the actual class before comparing addresses"""
+
+        import cppjit
+        from cppjit._pythonization import pin_type
+
+        cppjit.cppdef("""\
+        namespace PinnedCmp {
+            struct B1 { virtual ~B1() {} int a = 1; };
+            struct B2 { virtual ~B2() {} int b = 2; };
+            struct D : B1, B2 {};
+            D  g_d;
+            D*  get_d()  { return &g_d; }
+            B2* get_b2() { return static_cast<B2*>(&g_d); }
+        }""")
+
+        ns = cppjit.gbl.PinnedCmp
+
+        # pinning keeps the B2 proxy from being downcast on creation, so the
+        # B2 subobject address is what reaches the comparison
+        pin_type(ns.B2)
+        d, b2 = ns.get_d(), ns.get_b2()
+        assert type(b2).__cpp_name__ == "PinnedCmp::B2"
+
+        assert d == b2
+        assert not (d != b2)