Improve the "underlying C/C++ object has been deleted" message

python-tqt is reporting "underlying C/C++ object has been deleted". This
is rather unhelpful. A little code has been backported from the equivalent
source files in sip 4.19.23 to make it a little clearer about what is
going wrong (original author Riverbank Computing Limited
<info@riverbankcomputing.com>, licensed under GPL version 2 or 3).

Signed-off-by: aneejit1 <aneejit1@gmail.com>

siplib/sip-tqt.h

@@ -1432,6 +1432,7 @@ typedef struct _sipTQtAPI {
 #define SIP_SHARE_MAP       0x0040  /* If the map slot might be occupied. */
 #define SIP_CPP_HAS_REF     0x0080  /* If C/C++ has a reference. */
 #define SIP_POSSIBLE_PROXY  0x0100  /* If there might be a proxy slot. */
+#define SIP_CREATED         0x1000  /* If the C/C++ object has been created. */
 
 #define sipIsPyOwned(w)     ((w)->flags & SIP_PY_OWNED)
 #define sipSetPyOwned(w)    ((w)->flags |= SIP_PY_OWNED)
@@ -1446,6 +1447,7 @@ typedef struct _sipTQtAPI {
 #define sipResetCppHasRef(w)    ((w)->flags &= ~SIP_CPP_HAS_REF)
 #define sipPossibleProxy(w) ((w)->flags & SIP_POSSIBLE_PROXY)
 #define sipSetPossibleProxy(w)  ((w)->flags |= SIP_POSSIBLE_PROXY)
+#define sipWasCreated(sw)   ((sw)->flags & SIP_CREATED)
 
 
 #define SIP_TYPE_TYPE_MASK  0x0007  /* The type type mask. */

siplib/siplib.c

@@ -551,7 +551,7 @@ static int getSelfFromArgs(sipTypeDef *td, PyObject *args, int argnr,
         sipSimpleWrapper **selfp);
 static PyObject *createEnumMember(sipTypeDef *td, sipEnumMemberDef *enm);
 static int compareTypedefName(const void *key, const void *el);
-static int checkPointer(void *ptr);
+static int checkPointer(void *ptr, sipSimpleWrapper *sw);
 static void *cast_cpp_ptr(void *ptr, PyTypeObject *src_type,
         const sipTypeDef *dst_type);
 static void finalise(void);
@@ -1040,7 +1040,7 @@ static PyObject *callDtor(PyObject *self, PyObject *args)
 
     addr = getPtrTypeDef(sw, &ctd);
 
-    if (checkPointer(addr) < 0)
+    if (checkPointer(addr, sw) < 0)
         return NULL;
 
     if (PyObject_TypeCheck((PyObject *)sw, (PyTypeObject *)&sipWrapper_Type))
@@ -7418,7 +7418,7 @@ void *sip_api_get_cpp_ptr(sipSimpleWrapper *sw, const sipTypeDef *td)
 {
     void *ptr = sipGetAddress(sw);
 
-    if (checkPointer(ptr) < 0)
+    if (checkPointer(ptr, sw) < 0)
         return NULL;
 
     if (td != NULL)
@@ -7454,12 +7454,14 @@ static void *cast_cpp_ptr(void *ptr, PyTypeObject *src_type,
 /*
  * Check that a pointer is non-NULL.
  */
-static int checkPointer(void *ptr)
+static int checkPointer(void *ptr, sipSimpleWrapper *sw)
 {
     if (ptr == NULL)
     {
-        PyErr_SetString(PyExc_RuntimeError,
+        PyErr_Format(PyExc_RuntimeError, (sipWasCreated(sw) ?
-                "underlying C/C++ object has been deleted");
+                        "wrapped C/C++ object of type %s has been deleted" :
+                        "super-class __init__() of type %s was never called"),
+                Py_TYPE(sw)->tp_name);
         return -1;
     }
 
@@ -8701,7 +8703,7 @@ static int sipSimpleWrapper_init(sipSimpleWrapper *self, PyObject *args,
     }
 
     self->u.cppPtr = sipNew;
-    self->flags = sipFlags;
+    self->flags = sipFlags | SIP_CREATED;
 
     if (!sipNotInMap(self))
         sipOMAddObject(&cppPyMap, self);