[dynamo] support Python 3.13t (pytorch#149549)

A few bug fixes to get Dynamo mostly working with 3.13 nogil. Dynamo encounters internal CPython assert errors in older versions of 3.13. The fix has been landed on [CPython's 3.13 branch](https://github.com/python/cpython/tree/3.13) and will be included in 3.13.3 (https://peps.python.org/pep-0719/ - april 8). If you wish to try `torch.compile` on the latest 3.13 branch, you can comment out the error checking (i.e. https://github.com/pytorch/pytorch/blob/70b6cd4e11fe61f8f9d6229b6da510c4d91a992b/torch/__init__.py#L2535 and https://github.com/pytorch/pytorch/blob/70b6cd4e11fe61f8f9d6229b6da510c4d91a992b/torch/_dynamo/eval_frame.py#L899).

We will work on getting PyTorch CI up for Dynamo/dynamo-wrapped/inductor once 3.13.3 is available.

Pull Request resolved: pytorch#149549
Approved by: https://github.com/jansel

Author: williamwen42

torch/__init__.py

@@ -2532,9 +2532,14 @@ def foo(x):
     _C._log_api_usage_once("torch.compile")
     if sys.version_info >= (3, 14):
         raise RuntimeError("torch.compile is not supported on Python 3.14+")
-    elif sysconfig.get_config_var("Py_GIL_DISABLED") == 1:
+    elif sysconfig.get_config_var("Py_GIL_DISABLED") == 1 and sys.version_info < (
+        3,
+        13,
+        3,
+    ):
         raise RuntimeError(
-            "torch.compile is not supported on Python built with GIL disabled"
+            "torch.compile is not supported on Python < 3.13.3 built with GIL disabled. "
+            "Please use Python 3.13.3+."
         )
 
     # Decorator mode

torch/_dynamo/eval_frame.py

@@ -896,9 +896,14 @@ def __call__(self, fn):
 def check_if_dynamo_supported():
     if sys.version_info >= (3, 14):
         raise RuntimeError("Python 3.14+ not yet supported for torch.compile")
-    elif sysconfig.get_config_var("Py_GIL_DISABLED") == 1:
+    elif sysconfig.get_config_var("Py_GIL_DISABLED") == 1 and sys.version_info < (
+        3,
+        13,
+        3,
+    ):
         raise RuntimeError(
-            "torch.compile is not supported on Python built with GIL disabled"
+            "torch.compile is not supported on Python < 3.13.3 built with GIL disabled. "
+            "Please use Python 3.13.3+."
         )
 
 

torch/_inductor/codecache.py

@@ -2283,7 +2283,7 @@ class CppPythonBindingsCodeCache(CppCodeCache):
                 return NULL;
             }}
             #ifdef Py_GIL_DISABLED
-                PyUnstable_Module_SetGIL(mod, Py_MOD_GIL_NOT_USED);
+                PyUnstable_Module_SetGIL(module, Py_MOD_GIL_NOT_USED);
             #endif
             return module;
         }}

torch/csrc/dynamo/eval_frame.c

@@ -589,7 +589,10 @@ static PyObject* set_skip_guard_eval_unsafe(
 }
 
 static PyObject* get_eval_frame_callback_py(PyObject* dummy, PyObject* args) {
-  return eval_frame_callback_get();
+  // New reference
+  PyObject* callback = eval_frame_callback_get();
+  Py_INCREF(callback);
+  return callback;
 }
 
 static PyObject* reset_code(PyObject* dummy, PyObject* code) {

torch/csrc/dynamo/guards.cpp

@@ -940,13 +940,13 @@ std::string get_exception_message() {
   PyErr_Fetch(&ptype, &pvalue, &ptraceback);
 
   PyObject* exc_message_pyobj = PyObject_Str(pvalue);
-  const char* exc_message = PyUnicode_AsUTF8(exc_message_pyobj);
+  std::string exc_message = PyUnicode_AsUTF8(exc_message_pyobj);
 
   Py_DECREF(exc_message_pyobj);
   Py_XDECREF(ptype);
   Py_XDECREF(pvalue);
   Py_XDECREF(ptraceback);
-  return std::string(exc_message);
+  return exc_message;
 }
 
 bool is_immutable_object(py::handle example_value) {