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gh-133079: Remove Py_C_RECURSION_LIMIT & PyThreadState.c_recursion_remaining (GH-133080)

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Both were added in 3.13, are undocumented, and don't make sense in 3.14 due to
changes in the stack overflow detection machinery (gh-112282).

PEP 387 exception for skipping a deprecation period: https://github.com/python/steering-council/issues/288
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Petr Viktorin 2025-04-29 12:56:20 +02:00 • committed by GitHub
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5 changed files with 12 additions and 6 deletions
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7
Doc/whatsnew/3.14.rst
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@ -2280,3 +2280,10 @@ Removed
* Remove the private ``_Py_InitializeMain()`` function. It was a
:term:`provisional API` added to Python 3.8 by :pep:`587`.
(Contributed by Victor Stinner in :gh:`129033`.)
* The undocumented APIs :c:macro:`!Py_C_RECURSION_LIMIT` and
:c:member:`!PyThreadState.c_recursion_remaining`, added in 3.13, are removed
without a deprecation period.
Please use :c:func:`Py_EnterRecursiveCall` to guard against runaway recursion
in C code.
(Removed in :gh:`133079`, see also :gh:`130396`.)

4
Include/cpython/pystate.h
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@ -118,8 +118,6 @@ struct _ts {
int py_recursion_remaining;
int py_recursion_limit;
int c_recursion_remaining; /* Retained for backwards compatibility. Do not use */
int recursion_headroom; /* Allow 50 more calls to handle any errors. */
/* 'tracing' keeps track of the execution depth when tracing/profiling.
@ -210,8 +208,6 @@ struct _ts {
_PyRemoteDebuggerSupport remote_debugger_support;
};
# define Py_C_RECURSION_LIMIT 5000
/* other API */
/* Similar to PyThreadState_Get(), but don't issue a fatal error

3
Misc/NEWS.d/next/C_API/2025-04-28-13-27-48.gh-issue-133079.DJL2sK.rst Normal file
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@ -0,0 +1,3 @@
The undocumented APIs :c:macro:`!Py_C_RECURSION_LIMIT` and
:c:member:`!PyThreadState.c_recursion_remaining`, added in 3.13, are removed
without a deprecation period.

1
Python/pystate.c
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@ -1559,7 +1559,6 @@ init_threadstate(_PyThreadStateImpl *_tstate,
tstate->py_recursion_limit = interp->ceval.recursion_limit;
tstate->py_recursion_remaining = interp->ceval.recursion_limit;
tstate->c_recursion_remaining = 2;
tstate->exc_info = &tstate->exc_state;
// PyGILState_Release must not try to delete this thread state.

3
Python/vm-state.md
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@ -73,7 +73,8 @@ It will be more complex in the JIT.
Another important piece of VM state is the **thread state**, held in `tstate`.
The current frame pointer, `frame`, is always equal to `tstate->current_frame`.
The thread state also holds the exception state (`tstate->exc_info`) and the recursion counters (`tstate->c_recursion_remaining` and `tstate->py_recursion_remaining`).
The thread state also holds the exception state (`tstate->exc_info`) and
recursion tracking data (`tstate->py_recursion_remaining`, `tstate->c_stack*`).
The thread state is also used to access the **interpreter state** (`tstate->interp`), which is important since the "eval breaker" flags are stored there (`tstate->interp->ceval.eval_breaker`, an "atomic" variable), as well as the "PEP 523 function" (`tstate->interp->eval_frame`).
The interpreter state also holds the optimizer state (`optimizer` and some counters).