pythongh-111389: Make PyHASH_MULTIPLIER constant public

Author: vstinner

Doc/c-api/hash.rst

@@ -29,6 +29,12 @@ See also the :c:member:`PyTypeObject.tp_hash` member and :ref:`numeric-hash`.
 
    .. versionadded:: 3.13
 
+.. c:macro:: PyHASH_MULTIPLIER
+
+   Prime multiplier used in string and various other hashes.
+
+   .. versionadded:: 3.13
+
 .. c:macro:: PyHASH_INF
 
    The hash value returned for a positive infinity.

Include/cpython/pyhash.h

@@ -3,7 +3,7 @@
 #endif
 
 /* Prime multiplier used in string and various other hashes. */
-#define _PyHASH_MULTIPLIER 1000003UL  /* 0xf4243 */
+#define PyHASH_MULTIPLIER 1000003UL  /* 0xf4243 */
 
 /* Parameters used for the numeric hash implementation.  See notes for
    _Py_HashDouble in Python/pyhash.c.  Numeric hashes are based on
@@ -17,7 +17,7 @@
 
 #define PyHASH_MODULUS (((size_t)1 << _PyHASH_BITS) - 1)
 #define PyHASH_INF 314159
-#define PyHASH_IMAG _PyHASH_MULTIPLIER
+#define PyHASH_IMAG PyHASH_MULTIPLIER
 
 /* Aliases kept for backward compatibility with Python 3.12 */
 #define _PyHASH_BITS PyHASH_BITS

Misc/NEWS.d/next/C API/2024-05-20-10-35-22.gh-issue-111389.a6axBk.rst

@@ -0,0 +1,2 @@
+Add :c:macro:`PyHASH_MULTIPLIER` constant: prime multiplier used in string
+and various other hashes. Patch by Victor Stinner.