gh-101758: Add _PyState_AddModule() Back for the Stable ABI (gh-101956)

We're adding the function back, only for the stable ABI symbol and not as any form of API. I had removed it yesterday.

This undocumented "private" function was added with the implementation for PEP 3121 (3.0, 2007) for internal use and later moved out of the limited API (3.6, 2016) and then into the internal API (3.9, 2019). I removed it completely yesterday, including from the stable ABI manifest (where it was added because the symbol happened to be exported). It's unlikely that anyone is using _PyState_AddModule(), especially any stable ABI extensions built against 3.2-3.5, but we're playing it safe.

#101758

Author: ericsnowcurrently

Include/internal/pycore_pystate.h

@@ -152,6 +152,12 @@ extern void _PySignal_AfterFork(void);
 #endif
 
 
+PyAPI_FUNC(int) _PyState_AddModule(
+    PyThreadState *tstate,
+    PyObject* module,
+    PyModuleDef* def);
+
+
 PyAPI_FUNC(int) _PyOS_InterruptOccurred(PyThreadState *tstate);
 
 #define HEAD_LOCK(runtime) \

Lib/test/test_stable_abi_ctypes.py

@@ -1684,6 +1684,9 @@
 [function._PyObject_NewVar]
     added = '3.2'
     abi_only = true
+[function._PyState_AddModule]
+    added = '3.2'
+    abi_only = true
 [function._PyThreadState_Init]
     added = '3.2'
     abi_only = true

Misc/stable_abi.toml

@@ -487,6 +487,26 @@ PyState_FindModule(PyModuleDef* module)
     return _modules_by_index_get(interp, module);
 }
 
+/* _PyState_AddModule() has been completely removed from the C-API
+   (and was removed from the limited API in 3.6).  However, we're
+   playing it safe and keeping it around for any stable ABI extensions
+   built against 3.2-3.5. */
+int
+_PyState_AddModule(PyThreadState *tstate, PyObject* module, PyModuleDef* def)
+{
+    if (!def) {
+        assert(_PyErr_Occurred(tstate));
+        return -1;
+    }
+    if (def->m_slots) {
+        _PyErr_SetString(tstate,
+                         PyExc_SystemError,
+                         "PyState_AddModule called on module with slots");
+        return -1;
+    }
+    return _modules_by_index_set(tstate->interp, def, module);
+}
+
 int
 PyState_AddModule(PyObject* module, PyModuleDef* def)
 {