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bpo-46361: Fix "small" int caching #30583

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Merged
mdickinson merged 7 commits into from
Jan 16, 2022
Merged

bpo-46361: Fix "small" int caching #30583

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9db7e9b
Add failing regression tests
brandtbucher Jan 12, 2022
53c4db3
Make sure small ints are properly cached
brandtbucher Jan 12, 2022
027551e
Clean things up a bit
brandtbucher Jan 13, 2022
9eff226
Fix leak
brandtbucher Jan 13, 2022
9f0bad1
blurb add
brandtbucher Jan 13, 2022
37374b1
Switch to a simpler implementation
brandtbucher Jan 13, 2022
5d7ad60
Fixup
brandtbucher Jan 13, 2022
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Clean things up a bit
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@brandtbucher
brandtbucher committed Jan 13, 2022
commit 027551ec74e6c09c8fcd8d22da022734f95ab58a
5 changes: 2 additions & 3 deletions Lib/test/test_decimal.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2551,12 +2551,11 @@ def test_int(self):
self.assertRaises(ValueError, int, Decimal('snan'))
self.assertRaises(OverflowError, int, Decimal('inf'))
self.assertRaises(OverflowError, int, Decimal('-inf'))

@cpython_only
def test_small_ints(self):
# bpo-46361
Decimal = self.decimal.Decimal

# bpo-46361
for x in range(-5, 257):
self.assertIs(int(Decimal(x)), x)

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1 change: 0 additions & 1 deletion Lib/test/test_long.py
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Expand Up @@ -1477,7 +1477,6 @@ def test_from_bytes_small(self):
for i in range(-5, 257):
b = i.to_bytes(2, signed=True)
self.assertIs(int.from_bytes(b, signed=True), i)


def test_access_to_nonexistent_digit_0(self):
# http://bugs.python.org/issue14630: A bug in _PyLong_Copy meant that
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32 changes: 20 additions & 12 deletions Modules/_decimal/_decimal.c
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Expand Up @@ -31,6 +31,7 @@

#include <Python.h>
#include "pycore_pystate.h" // _PyThreadState_GET()
#include "pycore_long.h" // _PyLong_SMALL_INTS
#include "complexobject.h"
#include "mpdecimal.h"

Expand Down Expand Up @@ -3348,6 +3349,7 @@ dec_as_long(PyObject *dec, PyObject *context, int round)
PyLongObject *pylong;
digit *ob_digit;
size_t n;
Py_ssize_t i;
mpd_t *x;
mpd_context_t workctx;
uint32_t status = 0;
Expand Down Expand Up @@ -3387,36 +3389,42 @@ dec_as_long(PyObject *dec, PyObject *context, int round)
#error "PYLONG_BITS_IN_DIGIT should be 15 or 30"
#endif

Py_ssize_t sign = mpd_isnegative(x) && !mpd_iszero(x) ? -1 : 1;
mpd_del(x);

if (n == SIZE_MAX) {
PyErr_NoMemory();
mpd_del(x);
return NULL;
}

assert(n > 0);
while ((n > 0) && (ob_digit[n - 1] == 0)) {
n--;
}
Py_ssize_t sign = mpd_isnegative(x) && !mpd_iszero(x) ? -1 : 1;

if (n < 2) {
pylong = (PyLongObject *)PyLong_FromLong(sign * ob_digit[0]);
mpd_free(ob_digit);
return (PyObject *)pylong;
if (n == 1) {
sdigit value = sign * ob_digit[0];
// If this is a "small" int, use the cached instance:
if (-_PY_NSMALLNEGINTS <= value && value < _PY_NSMALLPOSINTS) {
mpd_free(ob_digit);
return Py_NewRef(&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS + value]);
}
}

assert(n > 0);
pylong = _PyLong_New(n);
if (pylong == NULL) {
mpd_free(ob_digit);
mpd_del(x);
return NULL;
}

memcpy(pylong->ob_digit, ob_digit, n * sizeof(digit));
mpd_free(ob_digit);

Py_SET_SIZE(pylong, sign * n);
i = n;
while ((i > 0) && (pylong->ob_digit[i-1] == 0)) {
i--;
}

Py_SET_SIZE(pylong, sign * i);

mpd_del(x);
return (PyObject *) pylong;
}

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