_Py_CheckRecursionLimit variable is no longer needed and can be removed. In Python 3.9, I added a recursion limit per interpreter. In Python 3.8 and older, it was used by _Py_MakeRecCheck() macro to check for recursion error. Previously, the _Py_CheckRecursionLimit variable was kept for backward compatibility with the stable ABI, but in Python 3.8 and older, Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() could not be used with the limited C API since these macros accessed PyThreadState structure member, whereas the structure is opaque in the limited C API. Attached PR removed the variable. --- (3) bpo-40513: Limit made per interpreter. commit 4e30ed3af06ae655f4cb8aad8cba21f341384250 Author: Victor Stinner <vstinner@python.org> Date: Tue May 5 16:52:52 2020 +0200 bpo-40513: Per-interpreter recursion_limit (GH-19929) Move recursion_limit member from _PyRuntimeState.ceval to PyInterpreterState.ceval. * Py_SetRecursionLimit() now only sets _Py_CheckRecursionLimit of ceval.c if the current Python thread is part of the main interpreter. * Inline _Py_MakeEndRecCheck() into _Py_LeaveRecursiveCall(). * Convert _Py_RecursionLimitLowerWaterMark() macro into a static inline function. --- (2) bpo-38644: The _Py_CheckRecursionLimit variable was used by Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() macros. I converted these macros into function calls in Python 3.9: commit f4b1e3d7c64985f5d5b00f6cc9a1c146bbbfd613 Author: Victor Stinner <vstinner@python.org> Date: Mon Nov 4 19:48:34 2019 +0100 bpo-38644: Add Py_EnterRecursiveCall() to the limited API (GH-17046) Provide Py_EnterRecursiveCall() and Py_LeaveRecursiveCall() as regular functions for the limited API. Previously, there were defined as macros, but these macros didn't work with the limited API which cannot access PyThreadState.recursion_depth field. Remove _Py_CheckRecursionLimit from the stable ABI. Add Include/cpython/ceval.h header file. In pycore_ceval.h, the function is overriden by a macro which points to an inline function which uses: * tstate->recursion_depth * tstate->interp->ceval.recursion_limit * tstate->stackcheck_counter (if USE_STACKCHECK macro is defined) --- (1) bpo-31857: Original change adding the FIXME. commit 1896793520a49a6f97ae360c0b288967e56b005e Author: pdox <pdox@alum.mit.edu> Date: Wed Oct 25 23:03:01 2017 -0700 bpo-31857: Make the behavior of USE_STACKCHECK deterministic (#4098) This change added the FIXME comment: /* Due to the macros in which it's used, _Py_CheckRecursionLimit is in the stable ABI. It should be removed therefrom when possible. */

 New changeset 19c3ac92bf73f1902cff846988552fd7bb8a8621 by Victor Stinner in branch 'master': bpo-41834: Remove _Py_CheckRecursionLimit variable (GH-22359) https://github.com/python/cpython/commit/19c3ac92bf73f1902cff846988552fd7bb8a8621