Backport of r51379 from trunk:

Add asserts to check for 'impossible' NULL values, with comments.
In one place where I'm not 1000% sure about the non-NULL, raise
a RuntimeError for safety.

This should fix the klocwork issues that Neal sent me.  If so,
it should be applied to the release25-maint branch also.

diff --git a/Modules/_ctypes/_ctypes.c b/Modules/_ctypes/_ctypes.c
index ab83f8ceacf6a3e9ebce35b9d4832883d3e53e7d..5204a7fa3457ae210e51c06eaafa6ad1b1afa6c4 100644 (file)
--- a/Modules/_ctypes/_ctypes.c
+++ b/Modules/_ctypes/_ctypes.c
@@ -672,6 +672,7 @@ PointerType_from_param(PyObject *type, PyObject *value)
                return PyInt_FromLong(0); /* NULL pointer */
 
        typedict = PyType_stgdict(type);
+       assert(typedict); /* Cannot be NULL for pointer types */
 
        /* If we expect POINTER(<type>), but receive a <type> instance, accept
           it by calling byref(<type>).
@@ -3129,6 +3130,13 @@ _build_callargs(CFuncPtrObject *self, PyObject *argtypes,
                        }
                        ob = PyTuple_GET_ITEM(argtypes, i);
                        dict = PyType_stgdict(ob);
+                       if (dict == NULL) {
+                               /* Cannot happen: _validate_paramflags()
+                                 would not accept such an object */
+                               PyErr_Format(PyExc_RuntimeError,
+                                            "NULL stgdict unexpected");
+                               goto error;
+                       }
                        if (PyString_Check(dict->proto)) {
                                PyErr_Format(
                                        PyExc_TypeError,
@@ -3726,6 +3734,8 @@ Array_slice(PyObject *_self, Py_ssize_t ilow, Py_ssize_t ihigh)
        assert(stgdict); /* Cannot be NULL for array object instances */
        proto = stgdict->proto;
        itemdict = PyType_stgdict(proto);
+       assert(itemdict); /* proto is the item type of the array, a ctypes
+                            type, so this cannot be NULL */
        if (itemdict->getfunc == getentry("c")->getfunc) {
                char *ptr = (char *)self->b_ptr;
                return PyString_FromStringAndSize(ptr + ilow, len);
@@ -4159,6 +4169,9 @@ Pointer_item(PyObject *_self, Py_ssize_t index)
        proto = stgdict->proto;
        assert(proto);
        itemdict = PyType_stgdict(proto);
+       assert(itemdict); /* proto is the item type of the pointer, a ctypes
+                            type, so this cannot be NULL */
+
        size = itemdict->size;
        offset = index * itemdict->size;
 
@@ -4194,6 +4207,9 @@ Pointer_ass_item(PyObject *_self, Py_ssize_t index, PyObject *value)
        assert(proto);
 
        itemdict = PyType_stgdict(proto);
+       assert(itemdict); /* Cannot be NULL because the itemtype of a pointer
+                            is always a ctypes type */
+
        size = itemdict->size;
        offset = index * itemdict->size;