gh-129983: fix data race in compile_template in sre.c (#130015)

diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-02-11-20-38-37.gh-issue-129983._1Fujo.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-11-20-38-37.gh-issue-129983._1Fujo.rst
new file mode 100644 (file)
index 0000000..9b43570
--- /dev/null
+++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-02-11-20-38-37.gh-issue-129983._1Fujo.rst
@@ -0,0 +1 @@
+Fix data race in compile_template in :file:`sre.c`.

diff --git a/Modules/_sre/sre.c b/Modules/_sre/sre.c
index 0d8d4843d33c1bc002c936e8c2bbfe8d26e7bc25..54f0e64d4819f1ad4a885e28f0d7cafebfc5c562 100644 (file)
--- a/Modules/_sre/sre.c
+++ b/Modules/_sre/sre.c
@@ -1167,13 +1167,21 @@ compile_template(_sremodulestate *module_state,
                  PatternObject *pattern, PyObject *template)
 {
     /* delegate to Python code */
-    PyObject *func = module_state->compile_template;
+    PyObject *func = FT_ATOMIC_LOAD_PTR(module_state->compile_template);
     if (func == NULL) {
         func = PyImport_ImportModuleAttrString("re", "_compile_template");
         if (func == NULL) {
             return NULL;
         }
+#ifdef Py_GIL_DISABLED
+        PyObject *other_func = NULL;
+        if (!_Py_atomic_compare_exchange_ptr(&module_state->compile_template, &other_func, func))  {
+            Py_DECREF(func);
+            func = other_func;
+        }
+#else
         Py_XSETREF(module_state->compile_template, func);
+#endif
     }
 
     PyObject *args[] = {(PyObject *)pattern, template};