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gh-132775: Add _PyObject_GetXIDataWithFallback() #133482

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Merged
merged 4 commits into from
May 21, 2025
Merged

gh-132775: Add _PyObject_GetXIDataWithFallback() #133482

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55ccaa0
Add _PyObject_GetXIDataWithFallback().
ericsnowcurrently Apr 25, 2025
d8b73ab
Py_UNREACHABLE() -> Py_FatalError().
ericsnowcurrently May 13, 2025
8e017f8
Fix typos.
ericsnowcurrently May 20, 2025
9693a5d
_PyObject_GetXIDataWithFallback -> _PyObject_GetXIData
ericsnowcurrently May 20, 2025
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25 changes: 23 additions & 2 deletions Include/internal/pycore_crossinterp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -131,7 +131,23 @@ PyAPI_FUNC(void) _PyXIData_Clear(PyInterpreterState *, _PyXIData_t *);

/* getting cross-interpreter data */

typedef int (*xidatafunc)(PyThreadState *tstate, PyObject *, _PyXIData_t *);
typedef int xidata_fallback_t;
#define _PyXIDATA_XIDATA_ONLY (0)
#define _PyXIDATA_FULL_FALLBACK (1)
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Maybe flags like 0b111?

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I added these with the idea that there is conceptual room for other options and the actual values aren't so important. However, they don't need to be unioned, so I'm not sure there's much value in using another literal form.


// Technically, we don't need two different function types;
// we could go with just the fallback one. However, only container
// types like tuple need it, so always having the extra arg would be
// a bit unfortunate. It's also nice to be able to clearly distinguish
// between types that might call _PyObject_GetXIData() and those that won't.
//
typedef int (*xidatafunc)(PyThreadState *, PyObject *, _PyXIData_t *);
typedef int (*xidatafbfunc)(
PyThreadState *, PyObject *, xidata_fallback_t, _PyXIData_t *);
typedef struct {
xidatafunc basic;
xidatafbfunc fallback;
} _PyXIData_getdata_t;
Comment on lines +147 to +150
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@neonene neonene May 16, 2025 •
edited
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Does the layout imply that it would accept two functions in the future? If exclusive, is there any reason why it cannot be a void pointer (or xidatafunc) with a flag? (The C compilers could verify xidatafbfunc at REGISTER_FALLBACK().)

E: No change request from me as long as there are only two options.

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Yeah, I tried both and went with this because I don't expect other options. This is internal API so I wasn't going to worry about it too much for now. That said, maybe it would be better to take the void * approach now. I'll think about it.

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I'm inclined to leave it the way it is, since I anticipate only those two options will be needed and it's nice to keep the signature explicit (instead of void *).


PyAPI_FUNC(PyObject *) _PyXIData_GetNotShareableErrorType(PyThreadState *);
PyAPI_FUNC(void) _PyXIData_SetNotShareableError(PyThreadState *, const char *);
Expand All @@ -140,16 +156,21 @@ PyAPI_FUNC(void) _PyXIData_FormatNotShareableError(
const char *,
...);

PyAPI_FUNC(xidatafunc) _PyXIData_Lookup(
PyAPI_FUNC(_PyXIData_getdata_t) _PyXIData_Lookup(
PyThreadState *,
PyObject *);
PyAPI_FUNC(int) _PyObject_CheckXIData(
PyThreadState *,
PyObject *);

PyAPI_FUNC(int) _PyObject_GetXIDataNoFallback(
PyThreadState *,
PyObject *,
_PyXIData_t *);
PyAPI_FUNC(int) _PyObject_GetXIData(
PyThreadState *,
PyObject *,
xidata_fallback_t,
_PyXIData_t *);

// _PyObject_GetXIData() for bytes
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4 changes: 2 additions & 2 deletions Include/internal/pycore_crossinterp_data_registry.h
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ typedef struct _xid_regitem {
/* This is NULL for builtin types. */
PyObject *weakref;
size_t refcount;
xidatafunc getdata;
_PyXIData_getdata_t getdata;
} _PyXIData_regitem_t;

typedef struct {
Expand All @@ -30,7 +30,7 @@ typedef struct {
PyAPI_FUNC(int) _PyXIData_RegisterClass(
PyThreadState *,
PyTypeObject *,
xidatafunc);
_PyXIData_getdata_t);
PyAPI_FUNC(int) _PyXIData_UnregisterClass(
PyThreadState *,
PyTypeObject *);
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2 changes: 1 addition & 1 deletion Lib/test/support/import_helper.py
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Expand Up @@ -438,5 +438,5 @@ def ensure_module_imported(name, *, clearnone=True):
if sys.modules.get(name) is not None:
mod = sys.modules[name]
else:
mod, _, _ = _force_import(name, False, True, clearnone)
mod, _, _ = _ensure_module(name, False, True, clearnone)
return mod
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