gh-110014: Remove PY_TIMEOUT_MAX from limited C API
diff --git a/Doc/data/stable_abi.dat b/Doc/data/stable_abi.dat
index 07c6d514d19549..c189c78238f40f 100644
--- a/Doc/data/stable_abi.dat
+++ b/Doc/data/stable_abi.dat
@@ -1,5 +1,4 @@
 role,name,added,ifdef_note,struct_abi_kind
-var,PY_TIMEOUT_MAX,3.2,,
 macro,PY_VECTORCALL_ARGUMENTS_OFFSET,3.12,,
 function,PyAIter_Check,3.10,,
 function,PyArg_Parse,3.2,,
diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
index 1de5479a924375..3a1b283a75bf2e 100644
--- a/Doc/whatsnew/3.13.rst
+++ b/Doc/whatsnew/3.13.rst
@@ -1290,3 +1290,6 @@ removed, although there is currently no date scheduled for their removal.
   * :c:func:`PyThread_get_key_value`: use :c:func:`PyThread_tss_get`.
   * :c:func:`PyThread_delete_key_value`: use :c:func:`PyThread_tss_delete`.
   * :c:func:`PyThread_ReInitTLS`: no longer needed.
+
+* Remove undocumented ``PY_TIMEOUT_MAX`` constant from the limited C API.
+  (Contributed by Victor Stinner in :gh:`110014`.)
diff --git a/Include/cpython/pythread.h b/Include/cpython/pythread.h
index cd2aab72d52df3..03f710a9f7ef2e 100644
--- a/Include/cpython/pythread.h
+++ b/Include/cpython/pythread.h
@@ -2,6 +2,14 @@
 #  error "this header file must not be included directly"
 #endif
 
+// PY_TIMEOUT_MAX is the highest usable value (in microseconds) of PY_TIMEOUT_T
+// type, and depends on the system threading API.
+//
+// NOTE: this isn't the same value as `_thread.TIMEOUT_MAX`. The _thread module
+// exposes a higher-level API, with timeouts expressed in seconds and
+// floating-point numbers allowed.
+PyAPI_DATA(const long long) PY_TIMEOUT_MAX;
+
 #define PYTHREAD_INVALID_THREAD_ID ((unsigned long)-1)
 
 #ifdef HAVE_PTHREAD_H
diff --git a/Include/pythread.h b/Include/pythread.h
index 2c2fd63d724286..0784f6b2e5391f 100644
--- a/Include/pythread.h
+++ b/Include/pythread.h
@@ -33,27 +33,18 @@ PyAPI_FUNC(int) PyThread_acquire_lock(PyThread_type_lock, int);
 #define WAIT_LOCK       1
 #define NOWAIT_LOCK     0
 
-/* PY_TIMEOUT_T is the integral type used to specify timeouts when waiting
-   on a lock (see PyThread_acquire_lock_timed() below).
-   PY_TIMEOUT_MAX is the highest usable value (in microseconds) of that
-   type, and depends on the system threading API.
-
-   NOTE: this isn't the same value as `_thread.TIMEOUT_MAX`.  The _thread
-   module exposes a higher-level API, with timeouts expressed in seconds
-   and floating-point numbers allowed.
-*/
+// PY_TIMEOUT_T is the integral type used to specify timeouts when waiting
+// on a lock (see PyThread_acquire_lock_timed() below).
 #define PY_TIMEOUT_T long long
 
-PyAPI_DATA(const long long) PY_TIMEOUT_MAX;
-
 
 /* If microseconds == 0, the call is non-blocking: it returns immediately
    even when the lock can't be acquired.
    If microseconds > 0, the call waits up to the specified duration.
    If microseconds < 0, the call waits until success (or abnormal failure)
 
-   microseconds must be less than PY_TIMEOUT_MAX. Behaviour otherwise is
-   undefined.
+   If *microseconds* is greater than PY_TIMEOUT_MAX, clamp the timeout to
+   PY_TIMEOUT_MAX microseconds.
 
    If intr_flag is true and the acquire is interrupted by a signal, then the
    call will return PY_LOCK_INTR.  The caller may reattempt to acquire the
diff --git a/Lib/test/test_stable_abi_ctypes.py b/Lib/test/test_stable_abi_ctypes.py
index 6e9496d40da477..94f817f8e1d159 100644
--- a/Lib/test/test_stable_abi_ctypes.py
+++ b/Lib/test/test_stable_abi_ctypes.py
@@ -35,7 +35,6 @@ def test_windows_feature_macros(self):
 
 SYMBOL_NAMES = (
 
-    "PY_TIMEOUT_MAX",
     "PyAIter_Check",
     "PyArg_Parse",
     "PyArg_ParseTuple",
diff --git a/Misc/NEWS.d/next/C API/2023-10-02-13-39-57.gh-issue-110014.gfQ4jU.rst b/Misc/NEWS.d/next/C API/2023-10-02-13-39-57.gh-issue-110014.gfQ4jU.rst
new file mode 100644
index 00000000000000..3a5ff7d43bbc01
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2023-10-02-13-39-57.gh-issue-110014.gfQ4jU.rst	
@@ -0,0 +1,2 @@
+Remove undocumented ``PY_TIMEOUT_MAX`` constant from the limited C API.
+Patch by Victor Stinner.
diff --git a/Misc/stable_abi.toml b/Misc/stable_abi.toml
index 46e2307614e26d..8df3f85e61eec6 100644
--- a/Misc/stable_abi.toml
+++ b/Misc/stable_abi.toml
@@ -1843,10 +1843,6 @@
 [function.PyThread_start_new_thread]
     added = '3.2'
 
-# Not mentioned in PEP 384, was implemented as a macro in Python <= 3.12
-[data.PY_TIMEOUT_MAX]
-    added = '3.2'
-
 # The following were added in PC/python3.def in Python 3.3:
 # 7800f75827b1be557be16f3b18f5170fbf9fae08
 # 9c56409d3353b8cd4cfc19e0467bbe23fd34fc92
diff --git a/PC/python3dll.c b/PC/python3dll.c
index 75728c7d8057ed..2c1cc8098ce856 100755
--- a/PC/python3dll.c
+++ b/PC/python3dll.c
@@ -768,7 +768,6 @@ EXPORT_DATA(Py_FileSystemDefaultEncodeErrors)
 EXPORT_DATA(Py_FileSystemDefaultEncoding)
 EXPORT_DATA(Py_GenericAliasType)
 EXPORT_DATA(Py_HasFileSystemDefaultEncoding)
-EXPORT_DATA(PY_TIMEOUT_MAX)
 EXPORT_DATA(Py_UTF8Mode)
 EXPORT_DATA(Py_Version)
 EXPORT_DATA(PyBaseObject_Type)

If the timeout is greater than PY_TIMEOUT_MAX,
PyThread_acquire_lock_timed() uses a timeout of PY_TIMEOUT_MAX microseconds, which is around 280.6 years. This case is unlikely and limiting a timeout to 280.6 years sounds like a reasonable trade-off.

The constant PY_TIMEOUT_MAX is not used in PyPI top 5,000 projects.

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* Issue: gh-110014
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