From 0f611aca8f3e372cefcfa5497f49b30b9b9eba7b Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Sun, 15 Nov 2026 12:13:25 +0100
Subject: [PATCH] Rework PyLong import/export functions

* Only call _PyLong_GetDigits() once in PyLongWriter_Finish().
* _PyLong_DigitCount() now uses Py_ABS(Py_SIZE(obj)).
* Enhance PyLong_Export() tests: test negative value and test
  PyObject_Str().
---
 pythoncapi_compat.h                 |  8 +++++---
 tests/test_pythoncapi_compat_cext.c | 11 ++++++++++-
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/pythoncapi_compat.h b/pythoncapi_compat.h
index 3fee8d2..a3521d4 100644
--- a/pythoncapi_compat.h
+++ b/pythoncapi_compat.h
@@ -2064,7 +2064,8 @@ _PyLong_DigitCount(const PyLongObject *op)
 #if PY_VERSION_HEX >= _Py_PACK_VERSION(3, 12)
     return (Py_ssize_t)(op->long_value.lv_tag >> 3);
 #else
-    return _PyLong_Sign((PyObject*)op) < 0 ? -Py_SIZE(op) : Py_SIZE(op);
+    Py_ssize_t size = Py_SIZE(op);
+    return Py_ABS(size);
 #endif
 }
 
@@ -2201,7 +2202,8 @@ PyLongWriter_Finish(PyLongWriter *writer)
     assert(Py_REFCNT(obj) == 1);
 
     // Normalize and get singleton if possible
-    while (i > 0 && _PyLong_GetDigits(self)[i-1] == 0) {
+    digit *digits = _PyLong_GetDigits(self);
+    while (i > 0 && digits[i-1] == 0) {
         --i;
     }
     if (i != j) {
@@ -2211,7 +2213,7 @@ PyLongWriter_Finish(PyLongWriter *writer)
         _PyLong_SetSignAndDigitCount(self, sign, i);
     }
     if (i <= 1) {
-        long val = sign * (long)(_PyLong_GetDigits(self)[0]);
+        long val = sign * (long)digits[0];
         Py_DECREF(obj);
         return PyLong_FromLong(val);
     }
diff --git a/tests/test_pythoncapi_compat_cext.c b/tests/test_pythoncapi_compat_cext.c
index 0f8039b..c75005b 100644
--- a/tests/test_pythoncapi_compat_cext.c
+++ b/tests/test_pythoncapi_compat_cext.c
@@ -1457,11 +1457,13 @@ test_long_import_export()
         return -1;
     }
     assert(long_export.value == -123);
+    assert(long_export.negative == 0);
+    assert(long_export.ndigits == 0);
     assert(long_export.digits == NULL);
     PyLong_FreeExport(&long_export);
     Py_DECREF(obj);
 
-    writer = PyLongWriter_Create(0, 5, (void **)&digits);
+    writer = PyLongWriter_Create(1, 5, (void **)&digits);
     if (writer == NULL) {
         return -1;
     }
@@ -1475,10 +1477,17 @@ test_long_import_export()
         return -1;
     }
 
+    PyObject *str = PyObject_Str(obj);
+    assert(str != NULL);
+    assert(PyUnicode_EqualToUTF8(str, "-1329227995784915872903807060280344577") == 1);
+    Py_DECREF(str);
+
     if (PyLong_Export(obj, &long_export) < 0) {
         return -1;
     }
     assert(long_export.value == 0);
+    assert(long_export.negative == 1);
+    assert(long_export.ndigits == 5);
     digits = (uint32_t*)long_export.digits;
     assert(digits[0] == 1);
     assert(digits[1] == 0);