gh-108867: Add PyThreadState_GetUnsafe() function

Add PyThreadState_GetUnsafe() function: similar to
PyThreadState_Get(), but don't issue a fatal error if it is NULL. The
caller is responsible to check if the result is NULL. Previously,
this function was private and known as _PyThreadState_UncheckedGet().

Author: vstinner

Doc/c-api/init.rst

@@ -871,6 +871,17 @@ code, or when embedding the Python interpreter:
    the caller needn't check for ``NULL``).
 
 
+.. c:function:: PyThreadState* PyThreadState_GetUnsafe()
+
+   Similar to :c:func:`PyThreadState_Get`, but don't kill the process with a
+   fatal error if it is NULL. The caller is responsible to check if the result
+   is NULL.
+
+   .. versionadded:: 3.13
+      In Python 3.5, the function was private and known as
+      ``_PyThreadState_UncheckedGet()``.
+
+
 .. c:function:: PyThreadState* PyThreadState_Swap(PyThreadState *tstate)
 
    Swap the current thread state with the thread state given by the argument

Doc/whatsnew/3.13.rst

@@ -924,6 +924,13 @@ New Features
   references) now supports the :ref:`Limited API <limited-c-api>`.
   (Contributed by Victor Stinner in :gh:`108634`.)
 
+* Add :c:func:`PyThreadState_GetUnsafe()` function: similar to
+  :c:func:`PyThreadState_Get()`, but don't kill the process with a fatal error
+  if it is NULL. The caller is responsible to check if the result is NULL.
+  Previously, the function was private and known as
+  ``_PyThreadState_UncheckedGet()``.
+  (Contributed by Victor Stinner in :gh:`108867`.)
+
 Porting to Python 3.13
 ----------------------
 

Include/cpython/object.h

@@ -425,7 +425,7 @@ PyAPI_FUNC(int) _PyTrash_cond(PyObject *op, destructor dealloc);
         /* If "cond" is false, then _tstate remains NULL and the deallocator \
          * is run normally without involving the trashcan */ \
         if (cond) { \
-            _tstate = _PyThreadState_UncheckedGet(); \
+            _tstate = PyThreadState_GetUnsafe(); \
             if (_PyTrash_begin(_tstate, _PyObject_CAST(op))) { \
                 break; \
             } \

Include/cpython/pystate.h

@@ -210,7 +210,7 @@ struct _ts {
 
 /* Similar to PyThreadState_Get(), but don't issue a fatal error
  * if it is NULL. */
-PyAPI_FUNC(PyThreadState *) _PyThreadState_UncheckedGet(void);
+PyAPI_FUNC(PyThreadState *) PyThreadState_GetUnsafe(void);
 
 // Disable tracing and profiling.
 PyAPI_FUNC(void) PyThreadState_EnterTracing(PyThreadState *tstate);

Include/internal/pycore_pystate.h

@@ -77,7 +77,7 @@ PyAPI_FUNC(PyThreadState *) _PyThreadState_GetCurrent(void);
 
    The caller must hold the GIL.
 
-   See also PyThreadState_Get() and _PyThreadState_UncheckedGet(). */
+   See also PyThreadState_Get() and PyThreadState_GetUnsafe(). */
 static inline PyThreadState*
 _PyThreadState_GET(void)
 {

Include/pystate.h

@@ -56,7 +56,7 @@ PyAPI_FUNC(void) PyThreadState_Delete(PyThreadState *);
 
    The caller must hold the GIL.
 
-   See also _PyThreadState_UncheckedGet() and _PyThreadState_GET(). */
+   See also PyThreadState_GetUnsafe() and _PyThreadState_GET(). */
 PyAPI_FUNC(PyThreadState *) PyThreadState_Get(void);
 
 // Alias to PyThreadState_Get()

Misc/NEWS.d/next/C API/2023-09-04-11-47-12.gh-issue-108867.Cr_LKd.rst

@@ -0,0 +1,5 @@
+Add :c:func:`PyThreadState_GetUnsafe()` function: similar to
+:c:`PyThreadState_Get()`, but don't kill the process with a fatal error if
+it is NULL. The caller is responsible to check if the result is NULL.
+Previously, the function was private and known as
+``_PyThreadState_UncheckedGet()``. Patch by Victor Stinner.

Modules/_testcapimodule.c

@@ -2445,8 +2445,8 @@ test_tstate_capi(PyObject *self, PyObject *Py_UNUSED(args))
     PyThreadState *tstate2 = PyThreadState_Get();
     assert(tstate2 == tstate);
 
-    // private _PyThreadState_UncheckedGet()
-    PyThreadState *tstate3 = _PyThreadState_UncheckedGet();
+    // PyThreadState_GetUnsafe()
+    PyThreadState *tstate3 = PyThreadState_GetUnsafe();
     assert(tstate3 == tstate);
 
     // PyThreadState_EnterTracing(), PyThreadState_LeaveTracing()

Modules/getpath.c

@@ -6,6 +6,7 @@
 #include "pycore_pathconfig.h"    // _PyPathConfig_ReadGlobal()
 #include "pycore_pyerrors.h"      // _PyErr_WriteUnraisableMsg()
 #include "pycore_pymem.h"         // _PyMem_RawWcsdup()
+#include "pycore_pystate.h"       // _PyThreadState_GET()
 
 #include "marshal.h"              // PyMarshal_ReadObjectFromString
 #include "osdefs.h"               // DELIM
@@ -821,7 +822,7 @@ _PyConfig_InitPathConfig(PyConfig *config, int compute_path_config)
         return status;
     }
 
-    if (!_PyThreadState_UncheckedGet()) {
+    if (!_PyThreadState_GET()) {
         return PyStatus_Error("cannot calculate path configuration without GIL");
     }
 

Python/pystate.c

@@ -1828,7 +1828,7 @@ PyThreadState_SetAsyncExc(unsigned long id, PyObject *exc)
 //---------------------------------
 
 PyThreadState *
-_PyThreadState_UncheckedGet(void)
+PyThreadState_GetUnsafe(void)
 {
     return current_fast_get(&_PyRuntime);
 }