[3.15] gh-152870: Fix compile error with decimal when EXTRA_FUNCTIONALITY enabled (GH-152871) (#152937)

gh-152870: Fix compile error with decimal when EXTRA_FUNCTIONALITY enabled (GH-152871)
(cherry picked from commit c4739533f3)

Co-authored-by: Xiaowei Lu <weixlu420302@gmail.com>

Lib/test/test_decimal.py

@@ -4967,6 +4967,14 @@ class CFunctionality(unittest.TestCase):
         self.assertEqual(c._flags, C.DecClamped)
         self.assertEqual(c._traps, C.DecRounded)
 
+    @requires_extra_functionality
+    def test_c_context_apply(self):
+        c = C.Context(prec=3)
+        self.assertEqual(c.apply(C.Decimal('1.23456')), C.Decimal('1.23'))
+        # A higher precision won't see them as equal.
+        c = C.Context(prec=5)
+        self.assertNotEqual(c.apply(C.Decimal('1.23456')), C.Decimal('1.23'))
+
     @requires_extra_functionality
     def test_constants(self):
         # Condition flags

Misc/NEWS.d/next/Build/2026-07-02-16-25-13.gh-issue-152870.oh9eD1.rst

@@ -0,0 +1,4 @@
+Fix a compilation error in the :mod:`decimal` C extension (``_decimal``) when
+it is built with ``EXTRA_FUNCTIONALITY``. ``Context.apply()`` called the
+internal ``_apply`` helper using its pre-Argument-Clinic signature; the call is
+now made through the generated ``_impl`` function.

Modules/_decimal/_decimal.c

@@ -6993,7 +6993,7 @@ _decimal_Context_apply_impl(PyObject *context, PyTypeObject *cls,
                             PyObject *x)
 /*[clinic end generated code: output=f8a7142d47ad4ff3 input=388e66ca82733516]*/
 {
-    return _decimal_Context__apply(context, x);
+    return _decimal_Context__apply_impl(context, cls, x);
 }
 #endif