From 0785c685599aaa052f85d6163872bdecb9c66486 Mon Sep 17 00:00:00 2001
From: Kirill Podoprigora <kirill.bast9@mail.ru>
Date: Thu, 30 Nov 2023 13:12:49 +0300
Subject: [PATCH] gh-111972: Make Unicode name C APIcapsule initialization
 thread-safe (#112249)

---
 Include/internal/pycore_ucnhash.h |  2 ++
 Objects/unicodeobject.c           | 32 ++++++++++++++++++++-----------
 Python/codecs.c                   | 12 +++---------
 3 files changed, 26 insertions(+), 20 deletions(-)

diff --git a/Include/internal/pycore_ucnhash.h b/Include/internal/pycore_ucnhash.h
index 187dd68e734..1561dfbb315 100644
--- a/Include/internal/pycore_ucnhash.h
+++ b/Include/internal/pycore_ucnhash.h
@@ -28,6 +28,8 @@ typedef struct {
 
 } _PyUnicode_Name_CAPI;
 
+extern _PyUnicode_Name_CAPI* _PyUnicode_GetNameCAPI(void);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index cffc06297a9..10022e23c04 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -5869,6 +5869,23 @@ PyUnicode_AsUTF16String(PyObject *unicode)
     return _PyUnicode_EncodeUTF16(unicode, NULL, 0);
 }
 
+_PyUnicode_Name_CAPI *
+_PyUnicode_GetNameCAPI(void)
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    _PyUnicode_Name_CAPI *ucnhash_capi;
+
+    ucnhash_capi = _Py_atomic_load_ptr(&interp->unicode.ucnhash_capi);
+    if (ucnhash_capi == NULL) {
+        ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
+                PyUnicodeData_CAPSULE_NAME, 1);
+
+        // It's fine if we overwite the value here. It's always the same value.
+        _Py_atomic_store_ptr(&interp->unicode.ucnhash_capi, ucnhash_capi);
+    }
+    return ucnhash_capi;
+}
+
 /* --- Unicode Escape Codec ----------------------------------------------- */
 
 PyObject *
@@ -5884,7 +5901,6 @@ _PyUnicode_DecodeUnicodeEscapeInternal(const char *s,
     PyObject *errorHandler = NULL;
     PyObject *exc = NULL;
     _PyUnicode_Name_CAPI *ucnhash_capi;
-    PyInterpreterState *interp = _PyInterpreterState_GET();
 
     // so we can remember if we've seen an invalid escape char or not
     *first_invalid_escape = NULL;
@@ -6032,19 +6048,13 @@ _PyUnicode_DecodeUnicodeEscapeInternal(const char *s,
 
             /* \N{name} */
         case 'N':
-            ucnhash_capi = interp->unicode.ucnhash_capi;
+            ucnhash_capi = _PyUnicode_GetNameCAPI();
             if (ucnhash_capi == NULL) {
-                /* load the unicode data module */
-                ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
-                                                PyUnicodeData_CAPSULE_NAME, 1);
-                if (ucnhash_capi == NULL) {
-                    PyErr_SetString(
+                PyErr_SetString(
                         PyExc_UnicodeError,
                         "\\N escapes not supported (can't load unicodedata module)"
-                        );
-                    goto onError;
-                }
-                interp->unicode.ucnhash_capi = ucnhash_capi;
+                );
+                goto onError;
             }
 
             message = "malformed \\N character escape";
diff --git a/Python/codecs.c b/Python/codecs.c
index 545bf82e00d..d8fe7b22063 100644
--- a/Python/codecs.c
+++ b/Python/codecs.c
@@ -931,8 +931,6 @@ PyObject *PyCodec_BackslashReplaceErrors(PyObject *exc)
     return Py_BuildValue("(Nn)", res, end);
 }
 
-static _PyUnicode_Name_CAPI *ucnhash_capi = NULL;
-
 PyObject *PyCodec_NameReplaceErrors(PyObject *exc)
 {
     if (PyObject_TypeCheck(exc, (PyTypeObject *)PyExc_UnicodeEncodeError)) {
@@ -953,13 +951,9 @@ PyObject *PyCodec_NameReplaceErrors(PyObject *exc)
             return NULL;
         if (!(object = PyUnicodeEncodeError_GetObject(exc)))
             return NULL;
-        if (!ucnhash_capi) {
-            /* load the unicode data module */
-            ucnhash_capi = (_PyUnicode_Name_CAPI *)PyCapsule_Import(
-                                            PyUnicodeData_CAPSULE_NAME, 1);
-            if (!ucnhash_capi) {
-                return NULL;
-            }
+        _PyUnicode_Name_CAPI *ucnhash_capi = _PyUnicode_GetNameCAPI();
+        if (ucnhash_capi == NULL) {
+            return NULL;
         }
         for (i = start, ressize = 0; i < end; ++i) {
             /* object is guaranteed to be "ready" */