Make PyUnstable_Unicode_GET_CACHED_HASH return -1 on PyPy (#157)

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: encukou

docs/api.rst

@@ -68,7 +68,7 @@ Python 3.15
 
    See `PyUnstable_Unicode_GET_CACHED_HASH() documentation  <https://docs.python.org/dev/c-api/unicode.html#c.PyUnstable_Unicode_GET_CACHED_HASH>`__.
 
-   Not available on PyPy.
+   On PyPy, always returns ``-1``.
 
 
 Python 3.14

pythoncapi_compat.h

@@ -2572,11 +2572,14 @@ PyTuple_FromArray(PyObject *const *array, Py_ssize_t size)
 #endif
 
 
-#if PY_VERSION_HEX < 0x030F00A1 && !defined(PYPY_VERSION)
+#if PY_VERSION_HEX < 0x030F00A1
 static inline Py_hash_t
 PyUnstable_Unicode_GET_CACHED_HASH(PyObject *op)
 {
-#if PY_VERSION_HEX >= 0x03000000
+#ifdef PYPY_VERSION
+    (void)op;  // unused argument
+    return -1;
+#elif PY_VERSION_HEX >= 0x03000000
     return ((PyASCIIObject*)op)->hash;
 #else
     return ((PyUnicodeObject*)op)->hash;

tests/test_pythoncapi_compat_cext.c

@@ -1611,8 +1611,10 @@ test_unicode(PyObject *Py_UNUSED(module), PyObject *Py_UNUSED(args))
     assert(PyErr_ExceptionMatches(PyExc_TypeError));
     PyErr_Clear();
 
-#ifndef PYPY_VERSION
     // Test PyUnstable_Unicode_GET_CACHED_HASH()
+#ifdef PYPY_VERSION
+    assert(PyUnstable_Unicode_GET_CACHED_HASH(abc) == -1);
+#else
     Py_hash_t hash = PyObject_Hash(abc);
     assert(hash != -1);
     assert(PyUnstable_Unicode_GET_CACHED_HASH(abc) == hash);