gh-76785: Crossinterp utils additions (gh-111530)

This moves several general internal APIs out of _xxsubinterpretersmodule.c and into the new Python/crossinterp.c (and the corresponding internal headers).

Specifically:

* _Py_excinfo, etc.:  the initial implementation for non-object exception snapshots (in pycore_pyerrors.h and Python/errors.c)
* _PyXI_exception_info, etc.:  helpers for passing an exception beween interpreters (wraps _Py_excinfo)
* _PyXI_namespace, etc.:  helpers for copying a dict of attrs between interpreters
* _PyXI_Enter(), _PyXI_Exit():  functions that abstract out the transitions between one interpreter and a second that will do some work temporarily

Again, these were all abstracted out of _xxsubinterpretersmodule.c as generalizations.  I plan on proposing these as public API at some point.

1 files changed, 7 insertions, 0 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 3c57056fb81..ea84ca0b9c3 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -738,6 +738,7 @@ pycore_init_types(PyInterpreterState *interp)
     if (_PyStatus_EXCEPTION(status)) {
         return status;
     }
+
     return _PyStatus_OK();
 }
 
@@ -854,6 +855,11 @@ pycore_interp_init(PyThreadState *tstate)
         goto done;
     }
 
+    status = _PyXI_Init(interp);
+    if (_PyStatus_EXCEPTION(status)) {
+        goto done;
+    }
+
     const PyConfig *config = _PyInterpreterState_GetConfig(interp);
 
     status = _PyImport_InitCore(tstate, sysmod, config->_install_importlib);
@@ -1772,6 +1778,7 @@ finalize_interp_clear(PyThreadState *tstate)
 {
     int is_main_interp = _Py_IsMainInterpreter(tstate->interp);
 
+    _PyXI_Fini(tstate->interp);
     _PyExc_ClearExceptionGroupType(tstate->interp);
     _Py_clear_generic_types(tstate->interp);