From 2dae505e87e3815f087d4b07a71bb2c5cce22304 Mon Sep 17 00:00:00 2001
From: Sam Gross <colesbury@gmail.com>
Date: Fri, 3 May 2024 11:09:57 -0400
Subject: gh-117514: Add `sys._is_gil_enabled()` function (#118514)

The function returns `True` or `False` depending on whether the GIL is
currently enabled. In the default build, it always returns `True`
because the GIL is always enabled.
---
 Doc/library/sys.rst                                |  8 ++++++
 Lib/test/test_sys.py                               |  6 +++++
 .../2024-05-02-16-04-51.gh-issue-117514.CJiuC0.rst |  4 +++
 Python/clinic/sysmodule.c.h                        | 30 +++++++++++++++++++++-
 Python/sysmodule.c                                 | 20 +++++++++++++++
 5 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2024-05-02-16-04-51.gh-issue-117514.CJiuC0.rst

diff --git a/Doc/library/sys.rst b/Doc/library/sys.rst
index 19d6856..91afa9d 100644
--- a/Doc/library/sys.rst
+++ b/Doc/library/sys.rst
@@ -1199,6 +1199,14 @@ always available.
    return value of :func:`intern` around to benefit from it.
 
 
+.. function:: _is_gil_enabled()
+
+   Return :const:`True` if the :term:`GIL` is enabled and :const:`False` if
+   it is disabled.
+
+   .. versionadded:: 3.13
+
+
 .. function:: is_finalizing()
 
    Return :const:`True` if the main Python interpreter is
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 14ec51e..df0a6f0 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -1053,6 +1053,12 @@ class SysModuleTest(unittest.TestCase):
         c = sys.getallocatedblocks()
         self.assertIn(c, range(b - 50, b + 50))
 
+    def test_is_gil_enabled(self):
+        if support.Py_GIL_DISABLED:
+            self.assertIs(type(sys._is_gil_enabled()), bool)
+        else:
+            self.assertTrue(sys._is_gil_enabled())
+
     def test_is_finalizing(self):
         self.assertIs(sys.is_finalizing(), False)
         # Don't use the atexit module because _Py_Finalizing is only set
diff --git a/Misc/NEWS.d/next/Core and Builtins/2024-05-02-16-04-51.gh-issue-117514.CJiuC0.rst b/Misc/NEWS.d/next/Core and Builtins/2024-05-02-16-04-51.gh-issue-117514.CJiuC0.rst
new file mode 100644
index 0000000..fc162af
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2024-05-02-16-04-51.gh-issue-117514.CJiuC0.rst	
@@ -0,0 +1,4 @@
+Add ``sys._is_gil_enabled()`` function that returns whether the GIL is
+currently enabled.  In the default build it always returns ``True`` because
+the GIL is always enabled.  In the free-threaded build, it may return
+``True`` or ``False``.
diff --git a/Python/clinic/sysmodule.c.h b/Python/clinic/sysmodule.c.h
index 31f66e8..0a8704c 100644
--- a/Python/clinic/sysmodule.c.h
+++ b/Python/clinic/sysmodule.c.h
@@ -1485,6 +1485,34 @@ exit:
     return return_value;
 }
 
+PyDoc_STRVAR(sys__is_gil_enabled__doc__,
+"_is_gil_enabled($module, /)\n"
+"--\n"
+"\n"
+"Return True if the GIL is currently enabled and False otherwise.");
+
+#define SYS__IS_GIL_ENABLED_METHODDEF    \
+    {"_is_gil_enabled", (PyCFunction)sys__is_gil_enabled, METH_NOARGS, sys__is_gil_enabled__doc__},
+
+static int
+sys__is_gil_enabled_impl(PyObject *module);
+
+static PyObject *
+sys__is_gil_enabled(PyObject *module, PyObject *Py_UNUSED(ignored))
+{
+    PyObject *return_value = NULL;
+    int _return_value;
+
+    _return_value = sys__is_gil_enabled_impl(module);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyBool_FromLong((long)_return_value);
+
+exit:
+    return return_value;
+}
+
 #ifndef SYS_GETWINDOWSVERSION_METHODDEF
     #define SYS_GETWINDOWSVERSION_METHODDEF
 #endif /* !defined(SYS_GETWINDOWSVERSION_METHODDEF) */
@@ -1528,4 +1556,4 @@ exit:
 #ifndef SYS_GETANDROIDAPILEVEL_METHODDEF
     #define SYS_GETANDROIDAPILEVEL_METHODDEF
 #endif /* !defined(SYS_GETANDROIDAPILEVEL_METHODDEF) */
-/*[clinic end generated code: output=518424ee03e353b0 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=352ac7a0085e8a1f input=a9049054013a1b77]*/
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index d3fbfcd..f469f16 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -2393,6 +2393,25 @@ sys__get_cpu_count_config_impl(PyObject *module)
     return config->cpu_count;
 }
 
+/*[clinic input]
+sys._is_gil_enabled -> bool
+
+Return True if the GIL is currently enabled and False otherwise.
+[clinic start generated code]*/
+
+static int
+sys__is_gil_enabled_impl(PyObject *module)
+/*[clinic end generated code: output=57732cf53f5b9120 input=7e9c47f15a00e809]*/
+{
+#ifdef Py_GIL_DISABLED
+    PyInterpreterState *interp = _PyInterpreterState_GET();
+    return interp->ceval.gil->enabled;
+#else
+    return 1;
+#endif
+}
+
+
 static PerfMapState perf_map_state;
 
 PyAPI_FUNC(int) PyUnstable_PerfMapState_Init(void) {
@@ -2565,6 +2584,7 @@ static PyMethodDef sys_methods[] = {
     SYS__STATS_DUMP_METHODDEF
 #endif
     SYS__GET_CPU_COUNT_CONFIG_METHODDEF
+    SYS__IS_GIL_ENABLED_METHODDEF
     {NULL, NULL}  // sentinel
 };
 
-- 
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