bpo-39489: Remove COUNT_ALLOCS special build (pythonGH-18259)

Remove:

* COUNT_ALLOCS macro
* sys.getcounts() function
* SHOW_ALLOC_COUNT code in listobject.c
* SHOW_TRACK_COUNT code in tupleobject.c
* PyConfig.show_alloc_count field
* -X showalloccount command line option
* @test.support.requires_type_collecting decorator

Author: vstinner

Doc/c-api/init_config.rst

@@ -627,14 +627,6 @@ PyConfig
 
       ``python3 -m MODULE`` argument. Used by :c:func:`Py_RunMain`.
 
-   .. c:member:: int show_alloc_count
-
-      Show allocation counts at exit?
-
-      Set to 1 by :option:`-X showalloccount <-X>` command line option.
-
-      Need a special Python build with ``COUNT_ALLOCS`` macro defined.
-
    .. c:member:: int show_ref_count
 
       Show total reference count at exit?
@@ -702,6 +694,10 @@ arguments are stripped from ``argv``: see :ref:`Command Line Arguments
 The ``xoptions`` options are parsed to set other options: see :option:`-X`
 option.
 
+.. versionchanged:: 3.9
+
+   The ``show_alloc_count`` field has been removed.
+
 
 Initialization with PyConfig
 ----------------------------

Doc/c-api/typeobj.rst

@@ -148,15 +148,6 @@ Quick Reference
    | :c:member:`~PyTypeObject.tp_vectorcall`        | :c:type:`vectorcallfunc`          |                   |   |   |   |   |
    +------------------------------------------------+-----------------------------------+-------------------+---+---+---+---+
 
-If :const:`COUNT_ALLOCS` is defined then the following (internal-only)
-fields exist as well:
-
-* :c:member:`~PyTypeObject.tp_allocs`
-* :c:member:`~PyTypeObject.tp_frees`
-* :c:member:`~PyTypeObject.tp_maxalloc`
-* :c:member:`~PyTypeObject.tp_prev`
-* :c:member:`~PyTypeObject.tp_next`
-
 .. [#slots]
    A slot name in parentheses indicates it is (effectively) deprecated.
    Names in angle brackets should be treated as read-only.
@@ -1904,31 +1895,6 @@ and :c:type:`PyType_Type` effectively act as defaults.)
    .. versionadded:: 3.9 (the field exists since 3.8 but it's only used since 3.9)
 
 
-The remaining fields are only defined if the feature test macro
-:const:`COUNT_ALLOCS` is defined, and are for internal use only. They are
-documented here for completeness.  None of these fields are inherited by
-subtypes.
-
-.. c:member:: Py_ssize_t PyTypeObject.tp_allocs
-
-   Number of allocations.
-
-.. c:member:: Py_ssize_t PyTypeObject.tp_frees
-
-   Number of frees.
-
-.. c:member:: Py_ssize_t PyTypeObject.tp_maxalloc
-
-   Maximum simultaneously allocated objects.
-
-.. c:member:: PyTypeObject* PyTypeObject.tp_prev
-
-   Pointer to the previous type object with a non-zero :c:member:`~PyTypeObject.tp_allocs` field.
-
-.. c:member:: PyTypeObject* PyTypeObject.tp_next
-
-   Pointer to the next type object with a non-zero :c:member:`~PyTypeObject.tp_allocs` field.
-
 Also, note that, in a garbage collected Python, :c:member:`~PyTypeObject.tp_dealloc` may be called from
 any Python thread, not just the thread which created the object (if the object
 becomes part of a refcount cycle, that cycle might be collected by a garbage

Doc/using/cmdline.rst

@@ -434,9 +434,6 @@ Miscellaneous options
      stored in a traceback of a trace. Use ``-X tracemalloc=NFRAME`` to start
      tracing with a traceback limit of *NFRAME* frames. See the
      :func:`tracemalloc.start` for more information.
-   * ``-X showalloccount`` to output the total count of allocated objects for
-     each type when the program finishes. This only works when Python was built with
-     ``COUNT_ALLOCS`` defined.
    * ``-X importtime`` to show how long each import takes. It shows module
      name, cumulative time (including nested imports) and self time (excluding
      nested imports).  Note that its output may be broken in multi-threaded
@@ -479,6 +476,8 @@ Miscellaneous options
       Using ``-X dev`` option, check *encoding* and *errors* arguments on
       string encoding and decoding operations.
 
+      The ``-X showalloccount`` option has been removed.
+
 
 Options you shouldn't use
 ~~~~~~~~~~~~~~~~~~~~~~~~~

Doc/whatsnew/3.9.rst

@@ -348,6 +348,9 @@ Build and C API Changes
   functions are now required to build Python.
   (Contributed by Victor Stinner in :issue:`39395`.)
 
+* The ``COUNT_ALLOCS`` special build macro has been removed.
+  (Contributed by Victor Stinner in :issue:`39489`.)
+
 
 Deprecated
 ==========
@@ -484,6 +487,12 @@ Removed
   ``asyncio.Condition`` and ``asyncio.Semaphore``.
   (Contributed by Andrew Svetlov in :issue:`34793`.)
 
+* The :func:`sys.getcounts` function, the ``-X showalloccount`` command line
+  option and the ``show_alloc_count`` field of the C structure
+  :c:type:`PyConfig` have been removed. They required a special Python build by
+  defining ``COUNT_ALLOCS`` macro.
+  (Contributed by Victor Stinner in :issue:`39489`.)
+
 
 Porting to Python 3.9
 =====================

Include/cpython/initconfig.h

@@ -153,7 +153,6 @@ typedef struct {
 
     int import_time;        /* PYTHONPROFILEIMPORTTIME, -X importtime */
     int show_ref_count;     /* -X showrefcount */
-    int show_alloc_count;   /* -X showalloccount */
     int dump_refs;          /* PYTHONDUMPREFS */
     int malloc_stats;       /* PYTHONMALLOCSTATS */
 

Include/cpython/object.h

@@ -255,15 +255,6 @@ typedef struct _typeobject {
 
     destructor tp_finalize;
     vectorcallfunc tp_vectorcall;
-
-#ifdef COUNT_ALLOCS
-    /* these must be last and never explicitly initialized */
-    Py_ssize_t tp_allocs;
-    Py_ssize_t tp_frees;
-    Py_ssize_t tp_maxalloc;
-    struct _typeobject *tp_prev;
-    struct _typeobject *tp_next;
-#endif
 } PyTypeObject;
 
 /* The *real* layout of a type object when allocated on the heap */
@@ -341,8 +332,6 @@ static inline void _Py_Dealloc_inline(PyObject *op)
     destructor dealloc = Py_TYPE(op)->tp_dealloc;
 #ifdef Py_TRACE_REFS
     _Py_ForgetReference(op);
-#else
-    _Py_INC_TPFREES(op);
 #endif
     (*dealloc)(op);
 }

Include/object.h

@@ -405,20 +405,6 @@ PyAPI_FUNC(void) _PyDebug_PrintTotalRefs(void);
 #define _Py_DEC_REFTOTAL
 #endif /* Py_REF_DEBUG */
 
-#ifdef COUNT_ALLOCS
-PyAPI_FUNC(void) _Py_inc_count(struct _typeobject *);
-PyAPI_FUNC(void) _Py_dec_count(struct _typeobject *);
-#define _Py_INC_TPALLOCS(OP)    _Py_inc_count(Py_TYPE(OP))
-#define _Py_INC_TPFREES(OP)     _Py_dec_count(Py_TYPE(OP))
-#define _Py_DEC_TPFREES(OP)     Py_TYPE(OP)->tp_frees--
-#define _Py_COUNT_ALLOCS_COMMA  ,
-#else
-#define _Py_INC_TPALLOCS(OP)
-#define _Py_INC_TPFREES(OP)
-#define _Py_DEC_TPFREES(OP)
-#define _Py_COUNT_ALLOCS_COMMA
-#endif /* COUNT_ALLOCS */
-
 /* Update the Python traceback of an object. This function must be called
    when a memory block is reused from a free list. */
 PyAPI_FUNC(int) _PyTraceMalloc_NewReference(PyObject *op);
@@ -438,15 +424,13 @@ static inline void _Py_NewReference(PyObject *op)
     if (_Py_tracemalloc_config.tracing) {
         _PyTraceMalloc_NewReference(op);
     }
-    _Py_INC_TPALLOCS(op);
     _Py_INC_REFTOTAL;
     Py_REFCNT(op) = 1;
 }
 
-static inline void _Py_ForgetReference(PyObject *op)
+static inline void _Py_ForgetReference(PyObject *Py_UNUSED(op))
 {
-    (void)op; /* may be unused, shut up -Wunused-parameter */
-    _Py_INC_TPFREES(op);
+    /* nothing to do */
 }
 #endif /* !Py_TRACE_REFS */
 

Lib/subprocess.py

@@ -325,7 +325,7 @@ def _args_from_interpreter_flags():
     if dev_mode:
         args.extend(('-X', 'dev'))
     for opt in ('faulthandler', 'tracemalloc', 'importtime',
-                'showalloccount', 'showrefcount', 'utf8'):
+                'showrefcount', 'utf8'):
         if opt in xoptions:
             value = xoptions[opt]
             if value is True:

Lib/test/support/__init__.py

@@ -2512,9 +2512,6 @@ def swap_item(obj, item, new_val):
             if item in obj:
                 del obj[item]
 
-requires_type_collecting = unittest.skipIf(hasattr(sys, 'getcounts'),
-                        'types are immortal if COUNT_ALLOCS is defined')
-
 def args_from_interpreter_flags():
     """Return a list of command-line arguments reproducing the current
     settings in sys.flags and sys.warnoptions."""

Lib/test/test_embed.py

@@ -356,7 +356,6 @@ class InitConfigTests(EmbeddingTestsMixin, unittest.TestCase):
         'tracemalloc': 0,
         'import_time': 0,
         'show_ref_count': 0,
-        'show_alloc_count': 0,
         'dump_refs': 0,
         'malloc_stats': 0,
 
@@ -729,7 +728,6 @@ def test_init_from_config(self):
             'tracemalloc': 2,
             'import_time': 1,
             'show_ref_count': 1,
-            'show_alloc_count': 1,
             'malloc_stats': 1,
 
             'stdio_encoding': 'iso8859-1',