path: root/ext/pybind11/include/pybind11/class_support.h

/*
    pybind11/class_support.h: Python C API implementation details for py::class_

    Copyright (c) 2017 Wenzel Jakob <wenzel.jakob@epfl.ch>

    All rights reserved. Use of this source code is governed by a
    BSD-style license that can be found in the LICENSE file.
*/

#pragma once

#include "attr.h"

NAMESPACE_BEGIN(pybind11)
NAMESPACE_BEGIN(detail)

#if !defined(PYPY_VERSION)

/// `pybind11_static_property.__get__()`: Always pass the class instead of the instance.
extern "C" inline PyObject *pybind11_static_get(PyObject *self, PyObject * /*ob*/, PyObject *cls) {
    return PyProperty_Type.tp_descr_get(self, cls, cls);
}

/// `pybind11_static_property.__set__()`: Just like the above `__get__()`.
extern "C" inline int pybind11_static_set(PyObject *self, PyObject *obj, PyObject *value) {
    PyObject *cls = PyType_Check(obj) ? obj : (PyObject *) Py_TYPE(obj);
    return PyProperty_Type.tp_descr_set(self, cls, value);
}

/** A `static_property` is the same as a `property` but the `__get__()` and `__set__()`
    methods are modified to always use the object type instead of a concrete instance.
    Return value: New reference. */
inline PyTypeObject *make_static_property_type() {
    constexpr auto *name = "pybind11_static_property";
    auto name_obj = reinterpret_steal<object>(PYBIND11_FROM_STRING(name));

    /* Danger zone: from now (and until PyType_Ready), make sure to
       issue no Python C API calls which could potentially invoke the
       garbage collector (the GC will call type_traverse(), which will in
       turn find the newly constructed type in an invalid state) */
    auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
    if (!heap_type)
        pybind11_fail("make_static_property_type(): error allocating type!");

    heap_type->ht_name = name_obj.inc_ref().ptr();
#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 3
    heap_type->ht_qualname = name_obj.inc_ref().ptr();
#endif

    auto type = &heap_type->ht_type;
    type->tp_name = name;
    type->tp_base = &PyProperty_Type;
    type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;
    type->tp_descr_get = pybind11_static_get;
    type->tp_descr_set = pybind11_static_set;

    if (PyType_Ready(type) < 0)
        pybind11_fail("make_static_property_type(): failure in PyType_Ready()!");

    setattr((PyObject *) type, "__module__", str("pybind11_builtins"));

    return type;
}

#else // PYPY

/** PyPy has some issues with the above C API, so we evaluate Python code instead.
    This function will only be called once so performance isn't really a concern.
    Return value: New reference. */
inline PyTypeObject *make_static_property_type() {
    auto d = dict();
    PyObject *result = PyRun_String(R"(\
        class pybind11_static_property(property):
            def __get__(self, obj, cls):
                return property.__get__(self, cls, cls)

            def __set__(self, obj, value):
                cls = obj if isinstance(obj, type) else type(obj)
                property.__set__(self, cls, value)
        )", Py_file_input, d.ptr(), d.ptr()
    );
    if (result == nullptr)
        throw error_already_set();
    Py_DECREF(result);
    return (PyTypeObject *) d["pybind11_static_property"].cast<object>().release().ptr();
}

#endif // PYPY

/** Inheriting from multiple C++ types in Python is not supported -- set an error instead.
    A Python definition (`class C(A, B): pass`) will call `tp_new` so we check for multiple
    C++ bases here. On the other hand, C++ type definitions (`py::class_<C, A, B>(m, "C")`)
    don't not use `tp_new` and will not trigger this error. */
extern "C" inline PyObject *pybind11_meta_new(PyTypeObject *metaclass, PyObject *args,
                                              PyObject *kwargs) {
    PyObject *bases = PyTuple_GetItem(args, 1); // arguments: (name, bases, dict)
    if (!bases)
        return nullptr;

    auto &internals = get_internals();
    auto num_cpp_bases = 0;
    for (auto base : reinterpret_borrow<tuple>(bases)) {
        auto base_type = (PyTypeObject *) base.ptr();
        auto instance_size = static_cast<size_t>(base_type->tp_basicsize);
        if (PyObject_IsSubclass(base.ptr(), internals.get_base(instance_size)))
            ++num_cpp_bases;
    }

    if (num_cpp_bases > 1) {
        PyErr_SetString(PyExc_TypeError, "Can't inherit from multiple C++ classes in Python."
                                         "Use py::class_ to define the class in C++ instead.");
        return nullptr;
    } else {
        return PyType_Type.tp_new(metaclass, args, kwargs);
    }
}

/** Types with static properties need to handle `Type.static_prop = x` in a specific way.
    By default, Python replaces the `static_property` itself, but for wrapped C++ types
    we need to call `static_property.__set__()` in order to propagate the new value to
    the underlying C++ data structure. */
extern "C" inline int pybind11_meta_setattro(PyObject* obj, PyObject* name, PyObject* value) {
    // Use `_PyType_Lookup()` instead of `PyObject_GetAttr()` in order to get the raw
    // descriptor (`property`) instead of calling `tp_descr_get` (`property.__get__()`).
    PyObject *descr = _PyType_Lookup((PyTypeObject *) obj, name);

    // Call `static_property.__set__()` instead of replacing the `static_property`.
    if (descr && PyObject_IsInstance(descr, (PyObject *) get_internals().static_property_type)) {
#if !defined(PYPY_VERSION)
        return Py_TYPE(descr)->tp_descr_set(descr, obj, value);
#else
        if (PyObject *result = PyObject_CallMethod(descr, "__set__", "OO", obj, value)) {
            Py_DECREF(result);
            return 0;
        } else {
            return -1;
        }
#endif
    } else {
        return PyType_Type.tp_setattro(obj, name, value);
    }
}

/** This metaclass is assigned by default to all pybind11 types and is required in order
    for static properties to function correctly. Users may override this using `py::metaclass`.
    Return value: New reference. */
inline PyTypeObject* make_default_metaclass() {
    constexpr auto *name = "pybind11_type";
    auto name_obj = reinterpret_steal<object>(PYBIND11_FROM_STRING(name));

    /* Danger zone: from now (and until PyType_Ready), make sure to
       issue no Python C API calls which could potentially invoke the
       garbage collector (the GC will call type_traverse(), which will in
       turn find the newly constructed type in an invalid state) */
    auto heap_type = (PyHeapTypeObject *) PyType_Type.tp_alloc(&PyType_Type, 0);
    if (!heap_type)
        pybind11_fail("make_default_metaclass(): error allocating metaclass!");

    heap_type->ht_name = name_obj.inc_ref().ptr();
#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 3
    heap_type->ht_qualname = name_obj.inc_ref().ptr();
#endif

    auto type = &heap_type->ht_type;
    type->tp_name = name;
    type->tp_base = &PyType_Type;
    type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;

    type->tp_new = pybind11_meta_new;
    type->tp_setattro = pybind11_meta_setattro;

    if (PyType_Ready(type) < 0)
        pybind11_fail("make_default_metaclass(): failure in PyType_Ready()!");

    setattr((PyObject *) type, "__module__", str("pybind11_builtins"));

    return type;
}

/// Instance creation function for all pybind11 types. It only allocates space for the
/// C++ object, but doesn't call the constructor -- an `__init__` function must do that.
extern "C" inline PyObject *pybind11_object_new(PyTypeObject *type, PyObject *, PyObject *) {
    PyObject *self = type->tp_alloc(type, 0);
    auto instance = (instance_essentials<void> *) self;
    auto tinfo = get_type_info(type);
    instance->value = tinfo->operator_new(tinfo->type_size);
    instance->owned = true;
    instance->holder_constructed = false;
    get_internals().registered_instances.emplace(instance->value, self);
    return self;
}

/// An `__init__` function constructs the C++ object. Users should provide at least one
/// of these using `py::init` or directly with `.def(__init__, ...)`. Otherwise, the
/// following default function will be used which simply throws an exception.
extern "C" inline int pybind11_object_init(PyObject *self, PyObject *, PyObject *) {
    PyTypeObject *type = Py_TYPE(self);
    std::string msg;
#if defined(PYPY_VERSION)
    msg += handle((PyObject *) type).attr("__module__").cast<std::string>() + ".";
#endif
    msg += type->tp_name;
    msg += ": No constructor defined!";
    PyErr_SetString(PyExc_TypeError, msg.c_str());
    return -1;
}

/// Instance destructor function for all pybind11 types. It calls `type_info.dealloc`
/// to destroy the C++ object itself, while the rest is Python bookkeeping.
extern "C" inline void pybind11_object_dealloc(PyObject *self) {
    auto instance = (instance_essentials<void> *) self;
    if (instance->value) {
        auto type = Py_TYPE(self);
        get_type_info(type)->dealloc(self);

        auto &registered_instances = get_internals().registered_instances;
        auto range = registered_instances.equal_range(instance->value);
        bool found = false;
        for (auto it = range.first; it != range.second; ++it) {
            if (type == Py_TYPE(it->second)) {
                registered_instances.erase(it);
                found = true;
                break;
            }
        }
        if (!found)
            pybind11_fail("pybind11_object_dealloc(): Tried to deallocate unregistered instance!");

        if (instance->weakrefs)
            PyObject_ClearWeakRefs(self);

        PyObject **dict_ptr = _PyObject_GetDictPtr(self);
        if (dict_ptr)
            Py_CLEAR(*dict_ptr);
    }
    Py_TYPE(self)->tp_free(self);
}

/** Create a type which can be used as a common base for all classes with the same
    instance size, i.e. all classes with the same `sizeof(holder_type)`. This is
    needed in order to satisfy Python's requirements for multiple inheritance.
    Return value: New reference. */
inline PyObject *make_object_base_type(size_t instance_size) {
    auto name = "pybind11_object_" + std::to_string(instance_size);
    auto name_obj = reinterpret_steal<object>(PYBIND11_FROM_STRING(name.c_str()));

    /* Danger zone: from now (and until PyType_Ready), make sure to
       issue no Python C API calls which could potentially invoke the
       garbage collector (the GC will call type_traverse(), which will in
       turn find the newly constructed type in an invalid state) */
    auto metaclass = get_internals().default_metaclass;
    auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
    if (!heap_type)
        pybind11_fail("make_object_base_type(): error allocating type!");

    heap_type->ht_name = name_obj.inc_ref().ptr();
#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 3
    heap_type->ht_qualname = name_obj.inc_ref().ptr();
#endif

    auto type = &heap_type->ht_type;
    type->tp_name = strdup(name.c_str());
    type->tp_base = &PyBaseObject_Type;
    type->tp_basicsize = static_cast<ssize_t>(instance_size);
    type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;

    type->tp_new = pybind11_object_new;
    type->tp_init = pybind11_object_init;
    type->tp_dealloc = pybind11_object_dealloc;

    /* Support weak references (needed for the keep_alive feature) */
    type->tp_weaklistoffset = offsetof(instance_essentials<void>, weakrefs);

    if (PyType_Ready(type) < 0)
        pybind11_fail("PyType_Ready failed in make_object_base_type():" + error_string());

    setattr((PyObject *) type, "__module__", str("pybind11_builtins"));

    assert(!PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));
    return (PyObject *) heap_type;
}

/** Return the appropriate base type for the given instance size. The results are cached
    in `internals.bases` so that only a single base is ever created for any size value.
    Return value: Borrowed reference. */
inline PyObject *internals::get_base(size_t instance_size) {
    auto it = bases.find(instance_size);
    if (it != bases.end()) {
        return it->second;
    } else {
        auto base = make_object_base_type(instance_size);
        bases[instance_size] = base;
        return base;
    }
}

/// dynamic_attr: Support for `d = instance.__dict__`.
extern "C" inline PyObject *pybind11_get_dict(PyObject *self, void *) {
    PyObject *&dict = *_PyObject_GetDictPtr(self);
    if (!dict)
        dict = PyDict_New();
    Py_XINCREF(dict);
    return dict;
}

/// dynamic_attr: Support for `instance.__dict__ = dict()`.
extern "C" inline int pybind11_set_dict(PyObject *self, PyObject *new_dict, void *) {
    if (!PyDict_Check(new_dict)) {
        PyErr_Format(PyExc_TypeError, "__dict__ must be set to a dictionary, not a '%.200s'",
                     Py_TYPE(new_dict)->tp_name);
        return -1;
    }
    PyObject *&dict = *_PyObject_GetDictPtr(self);
    Py_INCREF(new_dict);
    Py_CLEAR(dict);
    dict = new_dict;
    return 0;
}

/// dynamic_attr: Allow the garbage collector to traverse the internal instance `__dict__`.
extern "C" inline int pybind11_traverse(PyObject *self, visitproc visit, void *arg) {
    PyObject *&dict = *_PyObject_GetDictPtr(self);
    Py_VISIT(dict);
    return 0;
}

/// dynamic_attr: Allow the GC to clear the dictionary.
extern "C" inline int pybind11_clear(PyObject *self) {
    PyObject *&dict = *_PyObject_GetDictPtr(self);
    Py_CLEAR(dict);
    return 0;
}

/// Give instances of this type a `__dict__` and opt into garbage collection.
inline void enable_dynamic_attributes(PyHeapTypeObject *heap_type) {
    auto type = &heap_type->ht_type;
#if defined(PYPY_VERSION)
    pybind11_fail(std::string(type->tp_name) + ": dynamic attributes are "
                                               "currently not supported in "
                                               "conjunction with PyPy!");
#endif
    type->tp_flags |= Py_TPFLAGS_HAVE_GC;
    type->tp_dictoffset = type->tp_basicsize; // place dict at the end
    type->tp_basicsize += sizeof(PyObject *); // and allocate enough space for it
    type->tp_traverse = pybind11_traverse;
    type->tp_clear = pybind11_clear;

    static PyGetSetDef getset[] = {
        {const_cast<char*>("__dict__"), pybind11_get_dict, pybind11_set_dict, nullptr, nullptr},
        {nullptr, nullptr, nullptr, nullptr, nullptr}
    };
    type->tp_getset = getset;
}

/// buffer_protocol: Fill in the view as specified by flags.
extern "C" inline int pybind11_getbuffer(PyObject *obj, Py_buffer *view, int flags) {
    auto tinfo = get_type_info(Py_TYPE(obj));
    if (view == nullptr || obj == nullptr || !tinfo || !tinfo->get_buffer) {
        if (view)
            view->obj = nullptr;
        PyErr_SetString(PyExc_BufferError, "generic_type::getbuffer(): Internal error");
        return -1;
    }
    memset(view, 0, sizeof(Py_buffer));
    buffer_info *info = tinfo->get_buffer(obj, tinfo->get_buffer_data);
    view->obj = obj;
    view->ndim = 1;
    view->internal = info;
    view->buf = info->ptr;
    view->itemsize = (ssize_t) info->itemsize;
    view->len = view->itemsize;
    for (auto s : info->shape)
        view->len *= s;
    if ((flags & PyBUF_FORMAT) == PyBUF_FORMAT)
        view->format = const_cast<char *>(info->format.c_str());
    if ((flags & PyBUF_STRIDES) == PyBUF_STRIDES) {
        view->ndim = (int) info->ndim;
        view->strides = (ssize_t *) &info->strides[0];
        view->shape = (ssize_t *) &info->shape[0];
    }
    Py_INCREF(view->obj);
    return 0;
}

/// buffer_protocol: Release the resources of the buffer.
extern "C" inline void pybind11_releasebuffer(PyObject *, Py_buffer *view) {
    delete (buffer_info *) view->internal;
}

/// Give this type a buffer interface.
inline void enable_buffer_protocol(PyHeapTypeObject *heap_type) {
    heap_type->ht_type.tp_as_buffer = &heap_type->as_buffer;
#if PY_MAJOR_VERSION < 3
    heap_type->ht_type.tp_flags |= Py_TPFLAGS_HAVE_NEWBUFFER;
#endif

    heap_type->as_buffer.bf_getbuffer = pybind11_getbuffer;
    heap_type->as_buffer.bf_releasebuffer = pybind11_releasebuffer;
}

/** Create a brand new Python type according to the `type_record` specification.
    Return value: New reference. */
inline PyObject* make_new_python_type(const type_record &rec) {
    auto name = reinterpret_steal<object>(PYBIND11_FROM_STRING(rec.name));

#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 3
    auto ht_qualname = name;
    if (rec.scope && hasattr(rec.scope, "__qualname__")) {
        ht_qualname = reinterpret_steal<object>(
            PyUnicode_FromFormat("%U.%U", rec.scope.attr("__qualname__").ptr(), name.ptr()));
    }
#endif

    object module;
    if (rec.scope) {
        if (hasattr(rec.scope, "__module__"))
            module = rec.scope.attr("__module__");
        else if (hasattr(rec.scope, "__name__"))
            module = rec.scope.attr("__name__");
    }

#if !defined(PYPY_VERSION)
    const auto full_name = module ? str(module).cast<std::string>() + "." + rec.name
                                  : std::string(rec.name);
#else
    const auto full_name = std::string(rec.name);
#endif

    char *tp_doc = nullptr;
    if (rec.doc && options::show_user_defined_docstrings()) {
        /* Allocate memory for docstring (using PyObject_MALLOC, since
           Python will free this later on) */
        size_t size = strlen(rec.doc) + 1;
        tp_doc = (char *) PyObject_MALLOC(size);
        memcpy((void *) tp_doc, rec.doc, size);
    }

    auto &internals = get_internals();
    auto bases = tuple(rec.bases);
    auto base = (bases.size() == 0) ? internals.get_base(rec.instance_size)
                                    : bases[0].ptr();

    /* Danger zone: from now (and until PyType_Ready), make sure to
       issue no Python C API calls which could potentially invoke the
       garbage collector (the GC will call type_traverse(), which will in
       turn find the newly constructed type in an invalid state) */
    auto metaclass = rec.metaclass.ptr() ? (PyTypeObject *) rec.metaclass.ptr()
                                         : internals.default_metaclass;

    auto heap_type = (PyHeapTypeObject *) metaclass->tp_alloc(metaclass, 0);
    if (!heap_type)
        pybind11_fail(std::string(rec.name) + ": Unable to create type object!");

    heap_type->ht_name = name.release().ptr();
#if PY_MAJOR_VERSION >= 3 && PY_MINOR_VERSION >= 3
    heap_type->ht_qualname = ht_qualname.release().ptr();
#endif

    auto type = &heap_type->ht_type;
    type->tp_name = strdup(full_name.c_str());
    type->tp_doc = tp_doc;
    type->tp_base = (PyTypeObject *) handle(base).inc_ref().ptr();
    type->tp_basicsize = static_cast<ssize_t>(rec.instance_size);
    if (bases.size() > 0)
        type->tp_bases = bases.release().ptr();

    /* Don't inherit base __init__ */
    type->tp_init = pybind11_object_init;

    /* Supported protocols */
    type->tp_as_number = &heap_type->as_number;
    type->tp_as_sequence = &heap_type->as_sequence;
    type->tp_as_mapping = &heap_type->as_mapping;

    /* Flags */
    type->tp_flags |= Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HEAPTYPE;
#if PY_MAJOR_VERSION < 3
    type->tp_flags |= Py_TPFLAGS_CHECKTYPES;
#endif

    if (rec.dynamic_attr)
        enable_dynamic_attributes(heap_type);

    if (rec.buffer_protocol)
        enable_buffer_protocol(heap_type);

    if (PyType_Ready(type) < 0)
        pybind11_fail(std::string(rec.name) + ": PyType_Ready failed (" + error_string() + ")!");

    assert(rec.dynamic_attr ? PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC)
                            : !PyType_HasFeature(type, Py_TPFLAGS_HAVE_GC));

    /* Register type with the parent scope */
    if (rec.scope)
        setattr(rec.scope, rec.name, (PyObject *) type);

    if (module) // Needed by pydoc
        setattr((PyObject *) type, "__module__", module);

    return (PyObject *) type;
}

NAMESPACE_END(detail)
NAMESPACE_END(pybind11)