Include/abstract.h: Abstract Object Protocol

Include/abstract.h declares the generic dispatch layer that sits between the interpreter and type-specific slots. Every opcode that operates on an unknown object type (arithmetic, subscript, iteration) goes through one of these functions. Porting this header correctly is what makes operator overloading and duck-typed protocols work uniformly across built-in and user-defined types.

Map

Lines	Symbol	Kind	gopy location
1-50	PyObject_Call, PyObject_CallObject, PyObject_CallFunction	fn	objects/protocol.go
51-100	PyObject_CallMethod, PyObject_CallFunctionObjArgs	fn	objects/protocol.go
101-160	PyNumber_* (Add, Subtract, Multiply, etc.)	fn group	objects/protocol.go
161-220	PySequence_* (Length, GetItem, SetItem, Contains, etc.)	fn group	objects/protocol.go
221-280	PyMapping_* (Check, Size, GetItemString, Keys, etc.)	fn group	objects/protocol.go
281-320	PyIter_Next, PyObject_GetIter	fn	objects/protocol.go
321-360	PyObject_Dir, PyObject_IsInstance, PyObject_IsSubclass	fn	objects/protocol.go
361-400	PyObject_GetBuffer, PyBuffer_Release, Py_buffer struct	struct/fn	objects/protocol.go

Reading

PyObject_Call family

The call API has three layers of convenience, each building on the one below:

// Include/abstract.h:14
PyAPI_FUNC(PyObject *) PyObject_Call(
    PyObject *callable, PyObject *args, PyObject *kwargs);

// Include/abstract.h:28
PyAPI_FUNC(PyObject *) PyObject_CallObject(
    PyObject *callable, PyObject *args);

// Include/abstract.h:42
PyAPI_FUNC(PyObject *) PyObject_CallFunction(
    PyObject *callable, const char *format, ...);

// Include/abstract.h:58
PyAPI_FUNC(PyObject *) PyObject_CallMethod(
    PyObject *obj, const char *name, const char *format, ...);

PyObject_Call is the canonical entry point. CallObject passes NULL for kwargs. CallFunction and CallMethod accept a Py_BuildValue-style format string to construct the argument tuple inline.

Sequence, Mapping, and Number protocols

The three protocol families share a common pattern: each function checks the relevant slot (sq_item, mp_subscript, nb_add) and raises TypeError if absent.

// Include/abstract.h:168
PyAPI_FUNC(Py_ssize_t) PySequence_Length(PyObject *o);
PyAPI_FUNC(PyObject *)  PySequence_GetItem(PyObject *o, Py_ssize_t i);
PyAPI_FUNC(int)         PySequence_SetItem(PyObject *o, Py_ssize_t i, PyObject *v);
PyAPI_FUNC(int)         PySequence_Contains(PyObject *seq, PyObject *ob);

// Include/abstract.h:230
PyAPI_FUNC(int)         PyMapping_Check(PyObject *o);
PyAPI_FUNC(Py_ssize_t)  PyMapping_Size(PyObject *o);
PyAPI_FUNC(PyObject *)  PyMapping_GetItemString(PyObject *o, const char *key);
PyAPI_FUNC(PyObject *)  PyMapping_Keys(PyObject *o);

// Include/abstract.h:108
PyAPI_FUNC(PyObject *)  PyNumber_Add(PyObject *o1, PyObject *o2);
PyAPI_FUNC(PyObject *)  PyNumber_Subtract(PyObject *o1, PyObject *o2);
PyAPI_FUNC(PyObject *)  PyNumber_InPlaceAdd(PyObject *o1, PyObject *o2);

In-place variants (PyNumber_InPlaceAdd, etc.) attempt the nb_inplace_add slot first and fall back to nb_add when it is absent, matching the += semantics Python specifies.

Py_buffer and the buffer protocol

// Include/abstract.h:370
typedef struct bufferinfo {
    void      *buf;
    PyObject  *obj;
    Py_ssize_t len;
    Py_ssize_t itemsize;
    int        readonly;
    int        ndim;
    char      *format;
    Py_ssize_t *shape;
    Py_ssize_t *strides;
    Py_ssize_t *suboffsets;
    void      *internal;
} Py_buffer;

PyAPI_FUNC(int) PyObject_GetBuffer(PyObject *obj, Py_buffer *view, int flags);
PyAPI_FUNC(void) PyBuffer_Release(Py_buffer *view);

PyObject_GetBuffer fills the Py_buffer view by calling the type's bf_getbuffer slot. Callers must always pair it with PyBuffer_Release to decrement the exporter's reference count, even if the consumer only reads buf and len.

gopy notes

• All three protocol families dispatch through objects.Object's method set in objects/protocol.go. The Go interface Callable, Sequence, Mapping, and Number correspond directly to the CPython slot structs (PySequenceMethods, etc.).
• PyIter_Next maps to objects.IterNext which returns (Object, error). A StopIteration sentinel is converted to (nil, nil) following the same convention CPython uses internally after 3.7.
• The Py_buffer struct is not yet fully ported. PyObject_GetBuffer is stubbed for bytes and bytearray only. Strided and multi-dimensional buffers (ndim > 1) are deferred.
• PyObject_Dir calls __dir__ when defined, otherwise falls back to the type's tp_dir slot, then to a merge of __dict__ and MRO attributes. gopy follows the same three-step fallback in objects/protocol.go.