include/cpython/pystate.h

#ifndef Py_CPYTHON_PYSTATE_H
#  error "this header file must not be included directly"
#endif

PyAPI_FUNC(int) _PyInterpreterState_RequiresIDRef(PyInterpreterState *);
PyAPI_FUNC(void) _PyInterpreterState_RequireIDRef(PyInterpreterState *, int);

PyAPI_FUNC(PyObject *) _PyInterpreterState_GetMainModule(PyInterpreterState *);

/* State unique per thread */

/* Py_tracefunc return -1 when raising an exception, or 0 for success. */
typedef int (*Py_tracefunc)(PyObject *, PyFrameObject *, int, PyObject *);

/* The following values are used for 'what' for tracefunc functions
 *
 * To add a new kind of trace event, also update "trace_init" in
 * Python/sysmodule.c to define the Python level event name
 */
#define PyTrace_CALL 0
#define PyTrace_EXCEPTION 1
#define PyTrace_LINE 2
#define PyTrace_RETURN 3
#define PyTrace_C_CALL 4
#define PyTrace_C_EXCEPTION 5
#define PyTrace_C_RETURN 6
#define PyTrace_OPCODE 7


typedef struct _cframe {
    /* This struct will be threaded through the C stack
     * allowing fast access to per-thread state that needs
     * to be accessed quickly by the interpreter, but can
     * be modified outside of the interpreter.
     *
     * WARNING: This makes data on the C stack accessible from
     * heap objects. Care must be taken to maintain stack
     * discipline and make sure that instances of this struct cannot
     * accessed outside of their lifetime.
     */
    int use_tracing;
    struct _cframe *previous;
} CFrame;

typedef struct _err_stackitem {
    /* This struct represents an entry on the exception stack, which is a
     * per-coroutine state. (Coroutine in the computer science sense,
     * including the thread and generators).
     * This ensures that the exception state is not impacted by "yields"
     * from an except handler.
     */
    PyObject *exc_type, *exc_value, *exc_traceback;

    struct _err_stackitem *previous_item;

} _PyErr_StackItem;


// The PyThreadState typedef is in Include/pystate.h.
struct _ts {
    /* See Python/ceval.c for comments explaining most fields */

    struct _ts *prev;
    struct _ts *next;
    PyInterpreterState *interp;

    /* Borrowed reference to the current frame (it can be NULL) */
    PyFrameObject *frame;
    int recursion_depth;
    int recursion_headroom; /* Allow 50 more calls to handle any errors. */
    int stackcheck_counter;

    /* 'tracing' keeps track of the execution depth when tracing/profiling.
       This is to prevent the actual trace/profile code from being recorded in
       the trace/profile. */
    int tracing;

    /* Pointer to current CFrame in the C stack frame of the currently,
     * or most recently, executing _PyEval_EvalFrameDefault. */
    CFrame *cframe;

    Py_tracefunc c_profilefunc;
    Py_tracefunc c_tracefunc;
    PyObject *c_profileobj;
    PyObject *c_traceobj;

    /* The exception currently being raised */
    PyObject *curexc_type;
    PyObject *curexc_value;
    PyObject *curexc_traceback;

    /* The exception currently being handled, if no coroutines/generators
     * are present. Always last element on the stack referred to be exc_info.
     */
    _PyErr_StackItem exc_state;

    /* Pointer to the top of the stack of the exceptions currently
     * being handled */
    _PyErr_StackItem *exc_info;

    PyObject *dict;  /* Stores per-thread state */

    int gilstate_counter;

    PyObject *async_exc; /* Asynchronous exception to raise */
    unsigned long thread_id; /* Thread id where this tstate was created */

    int trash_delete_nesting;
    PyObject *trash_delete_later;

    /* Called when a thread state is deleted normally, but not when it
     * is destroyed after fork().
     * Pain:  to prevent rare but fatal shutdown errors (issue 18808),
     * Thread.join() must wait for the join'ed thread's tstate to be unlinked
     * from the tstate chain.  That happens at the end of a thread's life,
     * in pystate.c.
     * The obvious way doesn't quite work:  create a lock which the tstate
     * unlinking code releases, and have Thread.join() wait to acquire that
     * lock.  The problem is that we _are_ at the end of the thread's life:
     * if the thread holds the last reference to the lock, decref'ing the
     * lock will delete the lock, and that may trigger arbitrary Python code
     * if there's a weakref, with a callback, to the lock.  But by this time
     * _PyRuntime.gilstate.tstate_current is already NULL, so only the simplest
     * of C code can be allowed to run (in particular it must not be possible to
     * release the GIL).
     * So instead of holding the lock directly, the tstate holds a weakref to
     * the lock:  that's the value of on_delete_data below.  Decref'ing a
     * weakref is harmless.
     * on_delete points to _threadmodule.c's static release_sentinel() function.
     * After the tstate is unlinked, release_sentinel is called with the
     * weakref-to-lock (on_delete_data) argument, and release_sentinel releases
     * the indirectly held lock.
     */
    void (*on_delete)(void *);
    void *on_delete_data;

    int coroutine_origin_tracking_depth;

    PyObject *async_gen_firstiter;
    PyObject *async_gen_finalizer;

    PyObject *context;
    uint64_t context_ver;

    /* Unique thread state id. */
    uint64_t id;

    CFrame root_cframe;

    /* XXX signal handlers should also be here */

};

// Alias for backward compatibility with Python 3.8
#define _PyInterpreterState_Get PyInterpreterState_Get

PyAPI_FUNC(PyThreadState *) _PyThreadState_Prealloc(PyInterpreterState *);

/* Similar to PyThreadState_Get(), but don't issue a fatal error
 * if it is NULL. */
PyAPI_FUNC(PyThreadState *) _PyThreadState_UncheckedGet(void);

PyAPI_FUNC(PyObject *) _PyThreadState_GetDict(PyThreadState *tstate);

/* PyGILState */

/* Helper/diagnostic function - return 1 if the current thread
   currently holds the GIL, 0 otherwise.

   The function returns 1 if _PyGILState_check_enabled is non-zero. */
PyAPI_FUNC(int) PyGILState_Check(void);

/* Get the single PyInterpreterState used by this process' GILState
   implementation.

   This function doesn't check for error. Return NULL before _PyGILState_Init()
   is called and after _PyGILState_Fini() is called.

   See also _PyInterpreterState_Get() and _PyInterpreterState_GET(). */
PyAPI_FUNC(PyInterpreterState *) _PyGILState_GetInterpreterStateUnsafe(void);

/* The implementation of sys._current_frames()  Returns a dict mapping
   thread id to that thread's current frame.
*/
PyAPI_FUNC(PyObject *) _PyThread_CurrentFrames(void);

/* The implementation of sys._current_exceptions()  Returns a dict mapping
   thread id to that thread's current exception.
*/
PyAPI_FUNC(PyObject *) _PyThread_CurrentExceptions(void);

/* Routines for advanced debuggers, requested by David Beazley.
   Don't use unless you know what you are doing! */
PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_Main(void);
PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_Head(void);
PyAPI_FUNC(PyInterpreterState *) PyInterpreterState_Next(PyInterpreterState *);
PyAPI_FUNC(PyThreadState *) PyInterpreterState_ThreadHead(PyInterpreterState *);
PyAPI_FUNC(PyThreadState *) PyThreadState_Next(PyThreadState *);
PyAPI_FUNC(void) PyThreadState_DeleteCurrent(void);

/* Frame evaluation API */

typedef PyObject* (*_PyFrameEvalFunction)(PyThreadState *tstate, PyFrameObject *, int);

PyAPI_FUNC(_PyFrameEvalFunction) _PyInterpreterState_GetEvalFrameFunc(
    PyInterpreterState *interp);
PyAPI_FUNC(void) _PyInterpreterState_SetEvalFrameFunc(
    PyInterpreterState *interp,
    _PyFrameEvalFunction eval_frame);

PyAPI_FUNC(const PyConfig*) _PyInterpreterState_GetConfig(PyInterpreterState *interp);

/* Get a copy of the current interpreter configuration.

   Return 0 on success. Raise an exception and return -1 on error.

   The caller must initialize 'config', using PyConfig_InitPythonConfig()
   for example.

   Python must be preinitialized to call this method.
   The caller must hold the GIL. */
PyAPI_FUNC(int) _PyInterpreterState_GetConfigCopy(
    struct PyConfig *config);

/* Set the configuration of the current interpreter.

   This function should be called during or just after the Python
   initialization.

   Update the sys module with the new configuration. If the sys module was
   modified directly after the Python initialization, these changes are lost.

   Some configuration like faulthandler or warnoptions can be updated in the
   configuration, but don't reconfigure Python (don't enable/disable
   faulthandler and don't reconfigure warnings filters).

   Return 0 on success. Raise an exception and return -1 on error.

   The configuration should come from _PyInterpreterState_GetConfigCopy(). */
PyAPI_FUNC(int) _PyInterpreterState_SetConfig(
    const struct PyConfig *config);

// Get the configuration of the current interpreter.
// The caller must hold the GIL.
PyAPI_FUNC(const PyConfig*) _Py_GetConfig(void);


/* cross-interpreter data */

struct _xid;

// _PyCrossInterpreterData is similar to Py_buffer as an effectively
// opaque struct that holds data outside the object machinery.  This
// is necessary to pass safely between interpreters in the same process.
typedef struct _xid {
    // data is the cross-interpreter-safe derivation of a Python object
    // (see _PyObject_GetCrossInterpreterData).  It will be NULL if the
    // new_object func (below) encodes the data.
    void *data;
    // obj is the Python object from which the data was derived.  This
    // is non-NULL only if the data remains bound to the object in some
    // way, such that the object must be "released" (via a decref) when
    // the data is released.  In that case the code that sets the field,
    // likely a registered "crossinterpdatafunc", is responsible for
    // ensuring it owns the reference (i.e. incref).
    PyObject *obj;
    // interp is the ID of the owning interpreter of the original
    // object.  It corresponds to the active interpreter when
    // _PyObject_GetCrossInterpreterData() was called.  This should only
    // be set by the cross-interpreter machinery.
    //
    // We use the ID rather than the PyInterpreterState to avoid issues
    // with deleted interpreters.  Note that IDs are never re-used, so
    // each one will always correspond to a specific interpreter
    // (whether still alive or not).
    int64_t interp;
    // new_object is a function that returns a new object in the current
    // interpreter given the data.  The resulting object (a new
    // reference) will be equivalent to the original object.  This field
    // is required.
    PyObject *(*new_object)(struct _xid *);
    // free is called when the data is released.  If it is NULL then
    // nothing will be done to free the data.  For some types this is
    // okay (e.g. bytes) and for those types this field should be set
    // to NULL.  However, for most the data was allocated just for
    // cross-interpreter use, so it must be freed when
    // _PyCrossInterpreterData_Release is called or the memory will
    // leak.  In that case, at the very least this field should be set
    // to PyMem_RawFree (the default if not explicitly set to NULL).
    // The call will happen with the original interpreter activated.
    void (*free)(void *);
} _PyCrossInterpreterData;

PyAPI_FUNC(int) _PyObject_GetCrossInterpreterData(PyObject *, _PyCrossInterpreterData *);
PyAPI_FUNC(PyObject *) _PyCrossInterpreterData_NewObject(_PyCrossInterpreterData *);
PyAPI_FUNC(void) _PyCrossInterpreterData_Release(_PyCrossInterpreterData *);

PyAPI_FUNC(int) _PyObject_CheckCrossInterpreterData(PyObject *);

/* cross-interpreter data registry */

typedef int (*crossinterpdatafunc)(PyObject *, struct _xid *);

PyAPI_FUNC(int) _PyCrossInterpreterData_RegisterClass(PyTypeObject *, crossinterpdatafunc);
PyAPI_FUNC(crossinterpdatafunc) _PyCrossInterpreterData_Lookup(PyObject *);