bpo-43422: Revert _decimal C API addition (GH-24960)

Stefan Krah requested the reversal of these (unreleased) changes, quoting him:
> The capsule API does not meet my testing standards, since I've focused
on the upstream mpdecimal in the last couple of months.
> Additionally, I'd like to refine the API, perhaps together with the
Arrow community.

Automerge-Triggered-By: GH:pitrou

4 files changed, 19 insertions, 276 deletions

diff --git a/Modules/_decimal/_decimal.c b/Modules/_decimal/_decimal.c
index 664d45a..83e237d 100644
--- a/Modules/_decimal/_decimal.c
+++ b/Modules/_decimal/_decimal.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2020 Stefan Krah. All rights reserved.
+ * Copyright (c) 2008-2012 Stefan Krah. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
@@ -33,8 +33,6 @@
 
 #include <stdlib.h>
 
-#define CPYTHON_DECIMAL_MODULE
-#include "pydecimal.h"
 #include "docstrings.h"
 
 
@@ -5570,175 +5568,6 @@ static PyTypeObject PyDecContext_Type =
 };
 
 
-/****************************************************************************/
-/*                                   C-API                                  */
-/****************************************************************************/
-
-/* Simple API */
-static int
-PyDec_TypeCheck(const PyObject *v)
-{
-    return PyDec_Check(v);
-}
-
-static int
-PyDec_IsSpecial(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_IsSpecial: argument must be a Decimal");
-        return -1;
-    }
-
-    return mpd_isspecial(MPD(v));
-}
-
-static int
-PyDec_IsNaN(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_IsNaN: argument must be a Decimal");
-        return -1;
-    }
-
-    return mpd_isnan(MPD(v));
-}
-
-static int
-PyDec_IsInfinite(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_IsInfinite: argument must be a Decimal");
-        return -1;
-    }
-
-    return mpd_isinfinite(MPD(v));
-}
-
-static int64_t
-PyDec_GetDigits(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_GetDigits: argument must be a Decimal");
-        return -1;
-    }
-
-    return MPD(v)->digits;
-}
-
-static mpd_uint128_triple_t
-PyDec_AsUint128Triple(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        mpd_uint128_triple_t triple = { MPD_TRIPLE_ERROR, 0, 0, 0, 0 };
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_AsUint128Triple: argument must be a Decimal");
-        return triple;
-    }
-
-    return mpd_as_uint128_triple(MPD(v));
-}
-
-static PyObject *
-PyDec_FromUint128Triple(const mpd_uint128_triple_t *triple)
-{
-    PyObject *context;
-    PyObject *result;
-    uint32_t status = 0;
-
-    CURRENT_CONTEXT(context);
-
-    result = dec_alloc();
-    if (result == NULL) {
-        return NULL;
-    }
-
-    if (mpd_from_uint128_triple(MPD(result), triple, &status) < 0) {
-        if (dec_addstatus(context, status)) {
-            Py_DECREF(result);
-            return NULL;
-        }
-    }
-
-    return result;
-}
-
-/* Advanced API */
-static PyObject *
-PyDec_Alloc(void)
-{
-    return dec_alloc();
-}
-
-static mpd_t *
-PyDec_Get(PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_Get: argument must be a Decimal");
-        return NULL;
-    }
-
-    return MPD(v);
-}
-
-static const mpd_t *
-PyDec_GetConst(const PyObject *v)
-{
-    if (!PyDec_Check(v)) {
-        PyErr_SetString(PyExc_TypeError,
-            "PyDec_GetConst: argument must be a Decimal");
-        return NULL;
-    }
-
-    return MPD(v);
-}
-
-static void
-destroy_api(PyObject *capsule)
-{
-    void *capi = PyCapsule_GetPointer(capsule, PyDec_CAPSULE_NAME);
-    PyMem_Free(capi);
-}
-
-static PyObject *
-init_api(void)
-{
-    void **_decimal_api = PyMem_Calloc(CPYTHON_DECIMAL_MAX_API, sizeof(void *));
-    if (_decimal_api == NULL) {
-        PyErr_NoMemory();
-        return NULL;
-    }
-
-    /* Simple API */
-    _decimal_api[PyDec_TypeCheck_INDEX] = (void *)PyDec_TypeCheck;
-    _decimal_api[PyDec_IsSpecial_INDEX] = (void *)PyDec_IsSpecial;
-    _decimal_api[PyDec_IsNaN_INDEX] = (void *)PyDec_IsNaN;
-    _decimal_api[PyDec_IsInfinite_INDEX] = (void *)PyDec_IsInfinite;
-    _decimal_api[PyDec_GetDigits_INDEX] = (void *)PyDec_GetDigits;
-    _decimal_api[PyDec_AsUint128Triple_INDEX] = (void *)PyDec_AsUint128Triple;
-    _decimal_api[PyDec_FromUint128Triple_INDEX] = (void *)PyDec_FromUint128Triple;
-
-    /* Advanced API */
-    _decimal_api[PyDec_Alloc_INDEX] = (void *)PyDec_Alloc;
-    _decimal_api[PyDec_Get_INDEX] = (void *)PyDec_Get;
-    _decimal_api[PyDec_GetConst_INDEX] = (void *)PyDec_GetConst;
-
-    PyObject *capsule = PyCapsule_New(_decimal_api, PyDec_CAPSULE_NAME, destroy_api);
-    if (!capsule) {
-        PyMem_Free(_decimal_api);
-    }
-    return capsule;
-}
-
-
-/****************************************************************************/
-/*                                  Module                                  */
-/****************************************************************************/
-
 static PyMethodDef _decimal_methods [] =
 {
   { "getcontext", (PyCFunction)PyDec_GetCurrentContext, METH_NOARGS, doc_getcontext},
@@ -5849,27 +5678,17 @@ PyInit__decimal(void)
     DecCondMap *cm;
     struct ssize_constmap *ssize_cm;
     struct int_constmap *int_cm;
-    static PyObject *capsule = NULL;
-    static int initialized = 0;
     int i;
 
 
     /* Init libmpdec */
-    if (!initialized) {
-        mpd_traphandler = dec_traphandler;
-        mpd_mallocfunc = PyMem_Malloc;
-        mpd_reallocfunc = PyMem_Realloc;
-        mpd_callocfunc = mpd_callocfunc_em;
-        mpd_free = PyMem_Free;
-        mpd_setminalloc(_Py_DEC_MINALLOC);
-
-        capsule = init_api();
-        if (capsule == NULL) {
-            return NULL;
-        }
+    mpd_traphandler = dec_traphandler;
+    mpd_mallocfunc = PyMem_Malloc;
+    mpd_reallocfunc = PyMem_Realloc;
+    mpd_callocfunc = mpd_callocfunc_em;
+    mpd_free = PyMem_Free;
+    mpd_setminalloc(_Py_DEC_MINALLOC);
 
-        initialized = 1;
-    }
 
     /* Init external C-API functions */
     _py_long_multiply = PyLong_Type.tp_as_number->nb_multiply;
@@ -6094,10 +5913,6 @@ PyInit__decimal(void)
     CHECK_INT(PyModule_AddStringConstant(m, "__version__", "1.70"));
     CHECK_INT(PyModule_AddStringConstant(m, "__libmpdec_version__", mpd_version()));
 
-    /* Add capsule API */
-    if (PyModule_AddObjectRef(m, "_API", capsule) < 0) {
-        goto error;
-    }
 
     return m;
 
@@ -6121,7 +5936,6 @@ error:
     Py_CLEAR(basic_context_template); /* GCOV_NOT_REACHED */
     Py_CLEAR(extended_context_template); /* GCOV_NOT_REACHED */
     Py_CLEAR(m); /* GCOV_NOT_REACHED */
-    Py_CLEAR(capsule); /* GCOV_NOT_REACHED */
 
     return NULL; /* GCOV_NOT_REACHED */
 }
diff --git a/Modules/_decimal/tests/bench.py b/Modules/_decimal/tests/bench.py
index 88fd7b5..3726db1 100644
--- a/Modules/_decimal/tests/bench.py
+++ b/Modules/_decimal/tests/bench.py
@@ -7,10 +7,13 @@
 
 
 import time
+try:
+    from test.support import import_fresh_module
+except ImportError:
+    from test.test_support import import_fresh_module
 
-import _decimal as C
-import _pydecimal as P
-
+C = import_fresh_module('decimal', fresh=['_decimal'])
+P = import_fresh_module('decimal', blocked=['_decimal'])
 
 #
 # NOTE: This is the pi function from the decimal documentation, modified
diff --git a/Modules/_decimal/tests/deccheck.py b/Modules/_decimal/tests/deccheck.py
index 5de57d1..98ecd50 100644
--- a/Modules/_decimal/tests/deccheck.py
+++ b/Modules/_decimal/tests/deccheck.py
@@ -47,18 +47,14 @@ from subprocess import PIPE, STDOUT
 from queue import Queue, Empty
 from threading import Thread, Event, Lock
 
+from test.support import import_fresh_module
 from randdec import randfloat, all_unary, all_binary, all_ternary
 from randdec import unary_optarg, binary_optarg, ternary_optarg
 from formathelper import rand_format, rand_locale
 from _pydecimal import _dec_from_triple
 
-from _testcapi import decimal_as_triple
-from _testcapi import decimal_from_triple
-
-import _decimal as C
-import _pydecimal as P
-
-
+C = import_fresh_module('decimal', fresh=['_decimal'])
+P = import_fresh_module('decimal', blocked=['_decimal'])
 EXIT_STATUS = 0
 
 
@@ -162,45 +158,6 @@ TernaryRestricted = ['__pow__', 'context.power']
 
 
 # ======================================================================
-#                            Triple tests
-# ======================================================================
-
-def c_as_triple(dec):
-    sign, hi, lo, exp = decimal_as_triple(dec)
-
-    coeff = hi * 2**64 + lo
-    return (sign, coeff, exp)
-
-def c_from_triple(triple):
-    sign, coeff, exp = triple
-
-    hi = coeff // 2**64
-    lo = coeff % 2**64
-    return decimal_from_triple((sign, hi, lo, exp))
-
-def p_as_triple(dec):
-    sign, digits, exp = dec.as_tuple()
-
-    s = "".join(str(d) for d in digits)
-    coeff = int(s) if s else 0
-
-    if coeff < 0 or coeff >= 2**128:
-        raise ValueError("value out of bounds for a uint128 triple")
-
-    return (sign, coeff, exp)
-
-def p_from_triple(triple):
-    sign, coeff, exp = triple
-
-    if coeff < 0 or coeff >= 2**128:
-        raise ValueError("value out of bounds for a uint128 triple")
-
-    digits = tuple(int(c) for c in str(coeff))
-
-    return P.Decimal((sign, digits, exp))
-
-
-# ======================================================================
 #                            Unified Context
 # ======================================================================
 
@@ -893,44 +850,12 @@ def verify(t, stat):
         t.presults.append(str(t.rp.imag))
         t.presults.append(str(t.rp.real))
 
-        ctriple = None
-        if str(t.rc) == str(t.rp): # see skip handler
-            try:
-                ctriple = c_as_triple(t.rc)
-            except ValueError:
-                try:
-                    ptriple = p_as_triple(t.rp)
-                except ValueError:
-                    pass
-                else:
-                    raise RuntimeError("ValueError not raised")
-            else:
-                cres = c_from_triple(ctriple)
-                t.cresults.append(ctriple)
-                t.cresults.append(str(cres))
-
-                ptriple = p_as_triple(t.rp)
-                pres = p_from_triple(ptriple)
-                t.presults.append(ptriple)
-                t.presults.append(str(pres))
-
         if t.with_maxcontext and isinstance(t.rmax, C.Decimal):
             t.maxresults.append(t.rmax.to_eng_string())
             t.maxresults.append(t.rmax.as_tuple())
             t.maxresults.append(str(t.rmax.imag))
             t.maxresults.append(str(t.rmax.real))
 
-            if ctriple is not None:
-                # NaN payloads etc. depend on precision and clamp.
-                if all_nan(t.rc) and all_nan(t.rmax):
-                    t.maxresults.append(ctriple)
-                    t.maxresults.append(str(cres))
-                else:
-                    maxtriple = c_as_triple(t.rmax)
-                    maxres = c_from_triple(maxtriple)
-                    t.maxresults.append(maxtriple)
-                    t.maxresults.append(str(maxres))
-
         nc = t.rc.number_class().lstrip('+-s')
         stat[nc] += 1
     else:
diff --git a/Modules/_decimal/tests/formathelper.py b/Modules/_decimal/tests/formathelper.py
index 482e02a..19b2aad 100644
--- a/Modules/_decimal/tests/formathelper.py
+++ b/Modules/_decimal/tests/formathelper.py
@@ -31,10 +31,11 @@
 
 import os, sys, locale, random
 import platform, subprocess
+from test.support import import_fresh_module
 from distutils.spawn import find_executable
 
-import _decimal as C
-import _pydecimal as P
+C = import_fresh_module('decimal', fresh=['_decimal'])
+P = import_fresh_module('decimal', blocked=['_decimal'])
 
 
 windows_lang_strings = [