Issue #14203: Remove obsolete support for view==NULL in PyBuffer_FillInfo()

and bytearray_getbuffer().  Both functions now raise BufferError in that
case.

Misc/NEWS

@@ -1560,6 +1560,10 @@ Build
 C API
 -----
 
+- Issue #14203: Remove obsolete support for view==NULL in PyBuffer_FillInfo()
+  and bytearray_getbuffer().  Both functions now raise BufferError in that
+  case.
+
 - Issue #22445: PyBuffer_IsContiguous() now implements precise contiguity
   tests, compatible with NumPy's NPY_RELAXED_STRIDES_CHECKING compilation
   flag.  Previously the function reported false negatives for corner cases.

Modules/_testcapimodule.c

@@ -2519,6 +2519,39 @@ test_from_contiguous(PyObject* self, PyObject *noargs)
     Py_RETURN_NONE;
 }
  
+static PyObject *
+test_pep3118_obsolete_write_locks(PyObject* self, PyObject *noargs)
+{
+    PyObject *b;
+    char *dummy[1];
+    int ret, match;
+
+    ret = PyBuffer_FillInfo(NULL, NULL, dummy, 1, 0, PyBUF_SIMPLE);
+    match = PyErr_Occurred() && PyErr_ExceptionMatches(PyExc_BufferError);
+    PyErr_Clear();
+    if (ret != -1 || match == 0)
+        goto error;
+
+    b = PyByteArray_FromStringAndSize("", 0);
+    if (b == NULL) {
+        return NULL;
+    }
+
+    ret = PyObject_GetBuffer(b, NULL, PyBUF_SIMPLE);
+    Py_DECREF(b);
+    match = PyErr_Occurred() && PyErr_ExceptionMatches(PyExc_BufferError);
+    PyErr_Clear();
+    if (ret != -1 || match == 0)
+        goto error;
+
+    Py_RETURN_NONE;
+
+error:
+    PyErr_SetString(TestError,
+        "test_pep3118_obsolete_write_locks: failure");
+    return NULL;
+}
+
 /* Test that the fatal error from not having a current thread doesn't
    cause an infinite loop.  Run via Lib/test/test_capi.py */
 static PyObject *
@@ -3179,6 +3212,7 @@ static PyMethodDef TestMethods[] = {
     {"test_unicode_compare_with_ascii", (PyCFunction)test_unicode_compare_with_ascii, METH_NOARGS},
     {"test_capsule", (PyCFunction)test_capsule, METH_NOARGS},
     {"test_from_contiguous", (PyCFunction)test_from_contiguous, METH_NOARGS},
+    {"test_pep3118_obsolete_write_locks", (PyCFunction)test_pep3118_obsolete_write_locks, METH_NOARGS},
     {"getargs_tuple",           getargs_tuple,                   METH_VARARGS},
     {"getargs_keywords", (PyCFunction)getargs_keywords,
       METH_VARARGS|METH_KEYWORDS},

Objects/abstract.c

@@ -612,7 +612,12 @@ int
 PyBuffer_FillInfo(Py_buffer *view, PyObject *obj, void *buf, Py_ssize_t len,
                   int readonly, int flags)
 {
-    if (view == NULL) return 0; /* XXX why not -1? */
+    if (view == NULL) {
+        PyErr_SetString(PyExc_BufferError,
+            "PyBuffer_FillInfo: view==NULL argument is obsolete");
+        return -1;
+    }
+
     if (((flags & PyBUF_WRITABLE) == PyBUF_WRITABLE) &&
         (readonly == 1)) {
         PyErr_SetString(PyExc_BufferError,

Objects/bytearrayobject.c

@@ -60,18 +60,17 @@ _getbytevalue(PyObject* arg, int *value)
 static int
 bytearray_getbuffer(PyByteArrayObject *obj, Py_buffer *view, int flags)
 {
-    int ret;
     void *ptr;
     if (view == NULL) {
-        obj->ob_exports++;
-        return 0;
+        PyErr_SetString(PyExc_BufferError,
+            "bytearray_getbuffer: view==NULL argument is obsolete");
+        return -1;
     }
     ptr = (void *) PyByteArray_AS_STRING(obj);
-    ret = PyBuffer_FillInfo(view, (PyObject*)obj, ptr, Py_SIZE(obj), 0, flags);
-    if (ret >= 0) {
-        obj->ob_exports++;
-    }
-    return ret;
+    /* cannot fail if view != NULL and readonly == 0 */
+    (void)PyBuffer_FillInfo(view, (PyObject*)obj, ptr, Py_SIZE(obj), 0, flags);
+    obj->ob_exports++;
+    return 0;
 }
 
 static void