2 pybind11/cast.h: Partial template specializations to cast between
5 Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
7 All rights reserved. Use of this source code is governed by a
8 BSD-style license that can be found in the LICENSE file.
14 #include "detail/typeid.h"
15 #include "detail/descr.h"
16 #include "detail/internals.h"
20 #include <type_traits>
22 #if defined(PYBIND11_CPP17)
23 # if defined(__has_include)
24 # if __has_include(<string_view>)
25 # define PYBIND11_HAS_STRING_VIEW
27 # elif defined(_MSC_VER)
28 # define PYBIND11_HAS_STRING_VIEW
31 #ifdef PYBIND11_HAS_STRING_VIEW
32 #include <string_view>
35 #if defined(__cpp_lib_char8_t) && __cpp_lib_char8_t >= 201811L
36 # define PYBIND11_HAS_U8STRING
39 NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
40 NAMESPACE_BEGIN(detail)
42 /// A life support system for temporary objects created by `type_caster::load()`.
43 /// Adding a patient will keep it alive up until the enclosing function returns.
44 class loader_life_support {
46 /// A new patient frame is created when a function is entered
47 loader_life_support() {
48 get_internals().loader_patient_stack.push_back(nullptr);
51 /// ... and destroyed after it returns
52 ~loader_life_support() {
53 auto &stack = get_internals().loader_patient_stack;
55 pybind11_fail("loader_life_support: internal error");
57 auto ptr = stack.back();
61 // A heuristic to reduce the stack's capacity (e.g. after long recursive calls)
62 if (stack.capacity() > 16 && stack.size() != 0 && stack.capacity() / stack.size() > 2)
63 stack.shrink_to_fit();
66 /// This can only be used inside a pybind11-bound function, either by `argument_loader`
67 /// at argument preparation time or by `py::cast()` at execution time.
68 PYBIND11_NOINLINE static void add_patient(handle h) {
69 auto &stack = get_internals().loader_patient_stack;
71 throw cast_error("When called outside a bound function, py::cast() cannot "
72 "do Python -> C++ conversions which require the creation "
73 "of temporary values");
75 auto &list_ptr = stack.back();
76 if (list_ptr == nullptr) {
77 list_ptr = PyList_New(1);
79 pybind11_fail("loader_life_support: error allocating list");
80 PyList_SET_ITEM(list_ptr, 0, h.inc_ref().ptr());
82 auto result = PyList_Append(list_ptr, h.ptr());
84 pybind11_fail("loader_life_support: error adding patient");
89 // Gets the cache entry for the given type, creating it if necessary. The return value is the pair
90 // returned by emplace, i.e. an iterator for the entry and a bool set to `true` if the entry was
92 inline std::pair<decltype(internals::registered_types_py)::iterator, bool> all_type_info_get_cache(PyTypeObject *type);
94 // Populates a just-created cache entry.
95 PYBIND11_NOINLINE inline void all_type_info_populate(PyTypeObject *t, std::vector<type_info *> &bases) {
96 std::vector<PyTypeObject *> check;
97 for (handle parent : reinterpret_borrow<tuple>(t->tp_bases))
98 check.push_back((PyTypeObject *) parent.ptr());
100 auto const &type_dict = get_internals().registered_types_py;
101 for (size_t i = 0; i < check.size(); i++) {
102 auto type = check[i];
103 // Ignore Python2 old-style class super type:
104 if (!PyType_Check((PyObject *) type)) continue;
106 // Check `type` in the current set of registered python types:
107 auto it = type_dict.find(type);
108 if (it != type_dict.end()) {
109 // We found a cache entry for it, so it's either pybind-registered or has pre-computed
110 // pybind bases, but we have to make sure we haven't already seen the type(s) before: we
111 // want to follow Python/virtual C++ rules that there should only be one instance of a
113 for (auto *tinfo : it->second) {
114 // NB: Could use a second set here, rather than doing a linear search, but since
115 // having a large number of immediate pybind11-registered types seems fairly
116 // unlikely, that probably isn't worthwhile.
118 for (auto *known : bases) {
119 if (known == tinfo) { found = true; break; }
121 if (!found) bases.push_back(tinfo);
124 else if (type->tp_bases) {
125 // It's some python type, so keep follow its bases classes to look for one or more
127 if (i + 1 == check.size()) {
128 // When we're at the end, we can pop off the current element to avoid growing
129 // `check` when adding just one base (which is typical--i.e. when there is no
130 // multiple inheritance)
134 for (handle parent : reinterpret_borrow<tuple>(type->tp_bases))
135 check.push_back((PyTypeObject *) parent.ptr());
141 * Extracts vector of type_info pointers of pybind-registered roots of the given Python type. Will
142 * be just 1 pybind type for the Python type of a pybind-registered class, or for any Python-side
143 * derived class that uses single inheritance. Will contain as many types as required for a Python
144 * class that uses multiple inheritance to inherit (directly or indirectly) from multiple
145 * pybind-registered classes. Will be empty if neither the type nor any base classes are
148 * The value is cached for the lifetime of the Python type.
150 inline const std::vector<detail::type_info *> &all_type_info(PyTypeObject *type) {
151 auto ins = all_type_info_get_cache(type);
153 // New cache entry: populate it
154 all_type_info_populate(type, ins.first->second);
156 return ins.first->second;
160 * Gets a single pybind11 type info for a python type. Returns nullptr if neither the type nor any
161 * ancestors are pybind11-registered. Throws an exception if there are multiple bases--use
162 * `all_type_info` instead if you want to support multiple bases.
164 PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) {
165 auto &bases = all_type_info(type);
166 if (bases.size() == 0)
168 if (bases.size() > 1)
169 pybind11_fail("pybind11::detail::get_type_info: type has multiple pybind11-registered bases");
170 return bases.front();
173 inline detail::type_info *get_local_type_info(const std::type_index &tp) {
174 auto &locals = registered_local_types_cpp();
175 auto it = locals.find(tp);
176 if (it != locals.end())
181 inline detail::type_info *get_global_type_info(const std::type_index &tp) {
182 auto &types = get_internals().registered_types_cpp;
183 auto it = types.find(tp);
184 if (it != types.end())
189 /// Return the type info for a given C++ type; on lookup failure can either throw or return nullptr.
190 PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_index &tp,
191 bool throw_if_missing = false) {
192 if (auto ltype = get_local_type_info(tp))
194 if (auto gtype = get_global_type_info(tp))
197 if (throw_if_missing) {
198 std::string tname = tp.name();
199 detail::clean_type_id(tname);
200 pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname + "\"");
205 PYBIND11_NOINLINE inline handle get_type_handle(const std::type_info &tp, bool throw_if_missing) {
206 detail::type_info *type_info = get_type_info(tp, throw_if_missing);
207 return handle(type_info ? ((PyObject *) type_info->type) : nullptr);
210 struct value_and_holder {
211 instance *inst = nullptr;
213 const detail::type_info *type = nullptr;
216 // Main constructor for a found value/holder:
217 value_and_holder(instance *i, const detail::type_info *type, size_t vpos, size_t index) :
218 inst{i}, index{index}, type{type},
219 vh{inst->simple_layout ? inst->simple_value_holder : &inst->nonsimple.values_and_holders[vpos]}
222 // Default constructor (used to signal a value-and-holder not found by get_value_and_holder())
223 value_and_holder() {}
225 // Used for past-the-end iterator
226 value_and_holder(size_t index) : index{index} {}
228 template <typename V = void> V *&value_ptr() const {
229 return reinterpret_cast<V *&>(vh[0]);
231 // True if this `value_and_holder` has a non-null value pointer
232 explicit operator bool() const { return value_ptr(); }
234 template <typename H> H &holder() const {
235 return reinterpret_cast<H &>(vh[1]);
237 bool holder_constructed() const {
238 return inst->simple_layout
239 ? inst->simple_holder_constructed
240 : inst->nonsimple.status[index] & instance::status_holder_constructed;
242 void set_holder_constructed(bool v = true) {
243 if (inst->simple_layout)
244 inst->simple_holder_constructed = v;
246 inst->nonsimple.status[index] |= instance::status_holder_constructed;
248 inst->nonsimple.status[index] &= (uint8_t) ~instance::status_holder_constructed;
250 bool instance_registered() const {
251 return inst->simple_layout
252 ? inst->simple_instance_registered
253 : inst->nonsimple.status[index] & instance::status_instance_registered;
255 void set_instance_registered(bool v = true) {
256 if (inst->simple_layout)
257 inst->simple_instance_registered = v;
259 inst->nonsimple.status[index] |= instance::status_instance_registered;
261 inst->nonsimple.status[index] &= (uint8_t) ~instance::status_instance_registered;
265 // Container for accessing and iterating over an instance's values/holders
266 struct values_and_holders {
269 using type_vec = std::vector<detail::type_info *>;
270 const type_vec &tinfo;
273 values_and_holders(instance *inst) : inst{inst}, tinfo(all_type_info(Py_TYPE(inst))) {}
277 instance *inst = nullptr;
278 const type_vec *types = nullptr;
279 value_and_holder curr;
280 friend struct values_and_holders;
281 iterator(instance *inst, const type_vec *tinfo)
282 : inst{inst}, types{tinfo},
283 curr(inst /* instance */,
284 types->empty() ? nullptr : (*types)[0] /* type info */,
285 0, /* vpos: (non-simple types only): the first vptr comes first */
288 // Past-the-end iterator:
289 iterator(size_t end) : curr(end) {}
291 bool operator==(const iterator &other) { return curr.index == other.curr.index; }
292 bool operator!=(const iterator &other) { return curr.index != other.curr.index; }
293 iterator &operator++() {
294 if (!inst->simple_layout)
295 curr.vh += 1 + (*types)[curr.index]->holder_size_in_ptrs;
297 curr.type = curr.index < types->size() ? (*types)[curr.index] : nullptr;
300 value_and_holder &operator*() { return curr; }
301 value_and_holder *operator->() { return &curr; }
304 iterator begin() { return iterator(inst, &tinfo); }
305 iterator end() { return iterator(tinfo.size()); }
307 iterator find(const type_info *find_type) {
308 auto it = begin(), endit = end();
309 while (it != endit && it->type != find_type) ++it;
313 size_t size() { return tinfo.size(); }
317 * Extracts C++ value and holder pointer references from an instance (which may contain multiple
318 * values/holders for python-side multiple inheritance) that match the given type. Throws an error
319 * if the given type (or ValueType, if omitted) is not a pybind11 base of the given instance. If
320 * `find_type` is omitted (or explicitly specified as nullptr) the first value/holder are returned,
321 * regardless of type (and the resulting .type will be nullptr).
323 * The returned object should be short-lived: in particular, it must not outlive the called-upon
326 PYBIND11_NOINLINE inline value_and_holder instance::get_value_and_holder(const type_info *find_type /*= nullptr default in common.h*/, bool throw_if_missing /*= true in common.h*/) {
327 // Optimize common case:
328 if (!find_type || Py_TYPE(this) == find_type->type)
329 return value_and_holder(this, find_type, 0, 0);
331 detail::values_and_holders vhs(this);
332 auto it = vhs.find(find_type);
336 if (!throw_if_missing)
337 return value_and_holder();
340 pybind11_fail("pybind11::detail::instance::get_value_and_holder: "
341 "type is not a pybind11 base of the given instance "
342 "(compile in debug mode for type details)");
344 pybind11_fail("pybind11::detail::instance::get_value_and_holder: `" +
345 std::string(find_type->type->tp_name) + "' is not a pybind11 base of the given `" +
346 std::string(Py_TYPE(this)->tp_name) + "' instance");
350 PYBIND11_NOINLINE inline void instance::allocate_layout() {
351 auto &tinfo = all_type_info(Py_TYPE(this));
353 const size_t n_types = tinfo.size();
356 pybind11_fail("instance allocation failed: new instance has no pybind11-registered base types");
359 n_types == 1 && tinfo.front()->holder_size_in_ptrs <= instance_simple_holder_in_ptrs();
361 // Simple path: no python-side multiple inheritance, and a small-enough holder
363 simple_value_holder[0] = nullptr;
364 simple_holder_constructed = false;
365 simple_instance_registered = false;
367 else { // multiple base types or a too-large holder
368 // Allocate space to hold: [v1*][h1][v2*][h2]...[bb...] where [vN*] is a value pointer,
369 // [hN] is the (uninitialized) holder instance for value N, and [bb...] is a set of bool
370 // values that tracks whether each associated holder has been initialized. Each [block] is
371 // padded, if necessary, to an integer multiple of sizeof(void *).
373 for (auto t : tinfo) {
374 space += 1; // value pointer
375 space += t->holder_size_in_ptrs; // holder instance
377 size_t flags_at = space;
378 space += size_in_ptrs(n_types); // status bytes (holder_constructed and instance_registered)
380 // Allocate space for flags, values, and holders, and initialize it to 0 (flags and values,
381 // in particular, need to be 0). Use Python's memory allocation functions: in Python 3.6
382 // they default to using pymalloc, which is designed to be efficient for small allocations
383 // like the one we're doing here; in earlier versions (and for larger allocations) they are
384 // just wrappers around malloc.
385 #if PY_VERSION_HEX >= 0x03050000
386 nonsimple.values_and_holders = (void **) PyMem_Calloc(space, sizeof(void *));
387 if (!nonsimple.values_and_holders) throw std::bad_alloc();
389 nonsimple.values_and_holders = (void **) PyMem_New(void *, space);
390 if (!nonsimple.values_and_holders) throw std::bad_alloc();
391 std::memset(nonsimple.values_and_holders, 0, space * sizeof(void *));
393 nonsimple.status = reinterpret_cast<uint8_t *>(&nonsimple.values_and_holders[flags_at]);
398 PYBIND11_NOINLINE inline void instance::deallocate_layout() {
400 PyMem_Free(nonsimple.values_and_holders);
403 PYBIND11_NOINLINE inline bool isinstance_generic(handle obj, const std::type_info &tp) {
404 handle type = detail::get_type_handle(tp, false);
407 return isinstance(obj, type);
410 PYBIND11_NOINLINE inline std::string error_string() {
411 if (!PyErr_Occurred()) {
412 PyErr_SetString(PyExc_RuntimeError, "Unknown internal error occurred");
413 return "Unknown internal error occurred";
416 error_scope scope; // Preserve error state
418 std::string errorString;
420 errorString += handle(scope.type).attr("__name__").cast<std::string>();
424 errorString += (std::string) str(scope.value);
426 PyErr_NormalizeException(&scope.type, &scope.value, &scope.trace);
428 #if PY_MAJOR_VERSION >= 3
429 if (scope.trace != nullptr)
430 PyException_SetTraceback(scope.value, scope.trace);
433 #if !defined(PYPY_VERSION)
435 PyTracebackObject *trace = (PyTracebackObject *) scope.trace;
437 /* Get the deepest trace possible */
438 while (trace->tb_next)
439 trace = trace->tb_next;
441 PyFrameObject *frame = trace->tb_frame;
442 errorString += "\n\nAt:\n";
444 int lineno = PyFrame_GetLineNumber(frame);
446 " " + handle(frame->f_code->co_filename).cast<std::string>() +
447 "(" + std::to_string(lineno) + "): " +
448 handle(frame->f_code->co_name).cast<std::string>() + "\n";
449 frame = frame->f_back;
457 PYBIND11_NOINLINE inline handle get_object_handle(const void *ptr, const detail::type_info *type ) {
458 auto &instances = get_internals().registered_instances;
459 auto range = instances.equal_range(ptr);
460 for (auto it = range.first; it != range.second; ++it) {
461 for (auto vh : values_and_holders(it->second)) {
463 return handle((PyObject *) it->second);
469 inline PyThreadState *get_thread_state_unchecked() {
470 #if defined(PYPY_VERSION)
471 return PyThreadState_GET();
472 #elif PY_VERSION_HEX < 0x03000000
473 return _PyThreadState_Current;
474 #elif PY_VERSION_HEX < 0x03050000
475 return (PyThreadState*) _Py_atomic_load_relaxed(&_PyThreadState_Current);
476 #elif PY_VERSION_HEX < 0x03050200
477 return (PyThreadState*) _PyThreadState_Current.value;
479 return _PyThreadState_UncheckedGet();
483 // Forward declarations
484 inline void keep_alive_impl(handle nurse, handle patient);
485 inline PyObject *make_new_instance(PyTypeObject *type);
487 class type_caster_generic {
489 PYBIND11_NOINLINE type_caster_generic(const std::type_info &type_info)
490 : typeinfo(get_type_info(type_info)), cpptype(&type_info) { }
492 type_caster_generic(const type_info *typeinfo)
493 : typeinfo(typeinfo), cpptype(typeinfo ? typeinfo->cpptype : nullptr) { }
495 bool load(handle src, bool convert) {
496 return load_impl<type_caster_generic>(src, convert);
499 PYBIND11_NOINLINE static handle cast(const void *_src, return_value_policy policy, handle parent,
500 const detail::type_info *tinfo,
501 void *(*copy_constructor)(const void *),
502 void *(*move_constructor)(const void *),
503 const void *existing_holder = nullptr) {
504 if (!tinfo) // no type info: error will be set already
507 void *src = const_cast<void *>(_src);
509 return none().release();
511 auto it_instances = get_internals().registered_instances.equal_range(src);
512 for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
513 for (auto instance_type : detail::all_type_info(Py_TYPE(it_i->second))) {
514 if (instance_type && same_type(*instance_type->cpptype, *tinfo->cpptype))
515 return handle((PyObject *) it_i->second).inc_ref();
519 auto inst = reinterpret_steal<object>(make_new_instance(tinfo->type));
520 auto wrapper = reinterpret_cast<instance *>(inst.ptr());
521 wrapper->owned = false;
522 void *&valueptr = values_and_holders(wrapper).begin()->value_ptr();
525 case return_value_policy::automatic:
526 case return_value_policy::take_ownership:
528 wrapper->owned = true;
531 case return_value_policy::automatic_reference:
532 case return_value_policy::reference:
534 wrapper->owned = false;
537 case return_value_policy::copy:
538 if (copy_constructor)
539 valueptr = copy_constructor(src);
542 throw cast_error("return_value_policy = copy, but type is "
543 "non-copyable! (compile in debug mode for details)");
545 std::string type_name(tinfo->cpptype->name());
546 detail::clean_type_id(type_name);
547 throw cast_error("return_value_policy = copy, but type " +
548 type_name + " is non-copyable!");
551 wrapper->owned = true;
554 case return_value_policy::move:
555 if (move_constructor)
556 valueptr = move_constructor(src);
557 else if (copy_constructor)
558 valueptr = copy_constructor(src);
561 throw cast_error("return_value_policy = move, but type is neither "
562 "movable nor copyable! "
563 "(compile in debug mode for details)");
565 std::string type_name(tinfo->cpptype->name());
566 detail::clean_type_id(type_name);
567 throw cast_error("return_value_policy = move, but type " +
568 type_name + " is neither movable nor copyable!");
571 wrapper->owned = true;
574 case return_value_policy::reference_internal:
576 wrapper->owned = false;
577 keep_alive_impl(inst, parent);
581 throw cast_error("unhandled return_value_policy: should not happen!");
584 tinfo->init_instance(wrapper, existing_holder);
586 return inst.release();
589 // Base methods for generic caster; there are overridden in copyable_holder_caster
590 void load_value(value_and_holder &&v_h) {
591 auto *&vptr = v_h.value_ptr();
592 // Lazy allocation for unallocated values:
593 if (vptr == nullptr) {
594 auto *type = v_h.type ? v_h.type : typeinfo;
595 if (type->operator_new) {
596 vptr = type->operator_new(type->type_size);
598 #if defined(__cpp_aligned_new) && (!defined(_MSC_VER) || _MSC_VER >= 1912)
599 if (type->type_align > __STDCPP_DEFAULT_NEW_ALIGNMENT__)
600 vptr = ::operator new(type->type_size,
601 std::align_val_t(type->type_align));
604 vptr = ::operator new(type->type_size);
609 bool try_implicit_casts(handle src, bool convert) {
610 for (auto &cast : typeinfo->implicit_casts) {
611 type_caster_generic sub_caster(*cast.first);
612 if (sub_caster.load(src, convert)) {
613 value = cast.second(sub_caster.value);
619 bool try_direct_conversions(handle src) {
620 for (auto &converter : *typeinfo->direct_conversions) {
621 if (converter(src.ptr(), value))
626 void check_holder_compat() {}
628 PYBIND11_NOINLINE static void *local_load(PyObject *src, const type_info *ti) {
629 auto caster = type_caster_generic(ti);
630 if (caster.load(src, false))
635 /// Try to load with foreign typeinfo, if available. Used when there is no
636 /// native typeinfo, or when the native one wasn't able to produce a value.
637 PYBIND11_NOINLINE bool try_load_foreign_module_local(handle src) {
638 constexpr auto *local_key = PYBIND11_MODULE_LOCAL_ID;
639 const auto pytype = src.get_type();
640 if (!hasattr(pytype, local_key))
643 type_info *foreign_typeinfo = reinterpret_borrow<capsule>(getattr(pytype, local_key));
644 // Only consider this foreign loader if actually foreign and is a loader of the correct cpp type
645 if (foreign_typeinfo->module_local_load == &local_load
646 || (cpptype && !same_type(*cpptype, *foreign_typeinfo->cpptype)))
649 if (auto result = foreign_typeinfo->module_local_load(src.ptr(), foreign_typeinfo)) {
656 // Implementation of `load`; this takes the type of `this` so that it can dispatch the relevant
657 // bits of code between here and copyable_holder_caster where the two classes need different
658 // logic (without having to resort to virtual inheritance).
659 template <typename ThisT>
660 PYBIND11_NOINLINE bool load_impl(handle src, bool convert) {
661 if (!src) return false;
662 if (!typeinfo) return try_load_foreign_module_local(src);
664 // Defer accepting None to other overloads (if we aren't in convert mode):
665 if (!convert) return false;
670 auto &this_ = static_cast<ThisT &>(*this);
671 this_.check_holder_compat();
673 PyTypeObject *srctype = Py_TYPE(src.ptr());
675 // Case 1: If src is an exact type match for the target type then we can reinterpret_cast
676 // the instance's value pointer to the target type:
677 if (srctype == typeinfo->type) {
678 this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder());
681 // Case 2: We have a derived class
682 else if (PyType_IsSubtype(srctype, typeinfo->type)) {
683 auto &bases = all_type_info(srctype);
684 bool no_cpp_mi = typeinfo->simple_type;
686 // Case 2a: the python type is a Python-inherited derived class that inherits from just
687 // one simple (no MI) pybind11 class, or is an exact match, so the C++ instance is of
688 // the right type and we can use reinterpret_cast.
689 // (This is essentially the same as case 2b, but because not using multiple inheritance
690 // is extremely common, we handle it specially to avoid the loop iterator and type
691 // pointer lookup overhead)
692 if (bases.size() == 1 && (no_cpp_mi || bases.front()->type == typeinfo->type)) {
693 this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder());
696 // Case 2b: the python type inherits from multiple C++ bases. Check the bases to see if
697 // we can find an exact match (or, for a simple C++ type, an inherited match); if so, we
698 // can safely reinterpret_cast to the relevant pointer.
699 else if (bases.size() > 1) {
700 for (auto base : bases) {
701 if (no_cpp_mi ? PyType_IsSubtype(base->type, typeinfo->type) : base->type == typeinfo->type) {
702 this_.load_value(reinterpret_cast<instance *>(src.ptr())->get_value_and_holder(base));
708 // Case 2c: C++ multiple inheritance is involved and we couldn't find an exact type match
709 // in the registered bases, above, so try implicit casting (needed for proper C++ casting
710 // when MI is involved).
711 if (this_.try_implicit_casts(src, convert))
715 // Perform an implicit conversion
717 for (auto &converter : typeinfo->implicit_conversions) {
718 auto temp = reinterpret_steal<object>(converter(src.ptr(), typeinfo->type));
719 if (load_impl<ThisT>(temp, false)) {
720 loader_life_support::add_patient(temp);
724 if (this_.try_direct_conversions(src))
728 // Failed to match local typeinfo. Try again with global.
729 if (typeinfo->module_local) {
730 if (auto gtype = get_global_type_info(*typeinfo->cpptype)) {
732 return load(src, false);
736 // Global typeinfo has precedence over foreign module_local
737 return try_load_foreign_module_local(src);
741 // Called to do type lookup and wrap the pointer and type in a pair when a dynamic_cast
742 // isn't needed or can't be used. If the type is unknown, sets the error and returns a pair
743 // with .second = nullptr. (p.first = nullptr is not an error: it becomes None).
744 PYBIND11_NOINLINE static std::pair<const void *, const type_info *> src_and_type(
745 const void *src, const std::type_info &cast_type, const std::type_info *rtti_type = nullptr) {
746 if (auto *tpi = get_type_info(cast_type))
747 return {src, const_cast<const type_info *>(tpi)};
749 // Not found, set error:
750 std::string tname = rtti_type ? rtti_type->name() : cast_type.name();
751 detail::clean_type_id(tname);
752 std::string msg = "Unregistered type : " + tname;
753 PyErr_SetString(PyExc_TypeError, msg.c_str());
754 return {nullptr, nullptr};
757 const type_info *typeinfo = nullptr;
758 const std::type_info *cpptype = nullptr;
759 void *value = nullptr;
763 * Determine suitable casting operator for pointer-or-lvalue-casting type casters. The type caster
764 * needs to provide `operator T*()` and `operator T&()` operators.
766 * If the type supports moving the value away via an `operator T&&() &&` method, it should use
767 * `movable_cast_op_type` instead.
769 template <typename T>
771 conditional_t<std::is_pointer<remove_reference_t<T>>::value,
772 typename std::add_pointer<intrinsic_t<T>>::type,
773 typename std::add_lvalue_reference<intrinsic_t<T>>::type>;
776 * Determine suitable casting operator for a type caster with a movable value. Such a type caster
777 * needs to provide `operator T*()`, `operator T&()`, and `operator T&&() &&`. The latter will be
778 * called in appropriate contexts where the value can be moved rather than copied.
780 * These operator are automatically provided when using the PYBIND11_TYPE_CASTER macro.
782 template <typename T>
783 using movable_cast_op_type =
784 conditional_t<std::is_pointer<typename std::remove_reference<T>::type>::value,
785 typename std::add_pointer<intrinsic_t<T>>::type,
786 conditional_t<std::is_rvalue_reference<T>::value,
787 typename std::add_rvalue_reference<intrinsic_t<T>>::type,
788 typename std::add_lvalue_reference<intrinsic_t<T>>::type>>;
790 // std::is_copy_constructible isn't quite enough: it lets std::vector<T> (and similar) through when
791 // T is non-copyable, but code containing such a copy constructor fails to actually compile.
792 template <typename T, typename SFINAE = void> struct is_copy_constructible : std::is_copy_constructible<T> {};
794 // Specialization for types that appear to be copy constructible but also look like stl containers
795 // (we specifically check for: has `value_type` and `reference` with `reference = value_type&`): if
796 // so, copy constructability depends on whether the value_type is copy constructible.
797 template <typename Container> struct is_copy_constructible<Container, enable_if_t<all_of<
798 std::is_copy_constructible<Container>,
799 std::is_same<typename Container::value_type &, typename Container::reference>,
800 // Avoid infinite recursion
801 negation<std::is_same<Container, typename Container::value_type>>
802 >::value>> : is_copy_constructible<typename Container::value_type> {};
804 // Likewise for std::pair
805 // (after C++17 it is mandatory that the copy constructor not exist when the two types aren't themselves
806 // copy constructible, but this can not be relied upon when T1 or T2 are themselves containers).
807 template <typename T1, typename T2> struct is_copy_constructible<std::pair<T1, T2>>
808 : all_of<is_copy_constructible<T1>, is_copy_constructible<T2>> {};
810 // The same problems arise with std::is_copy_assignable, so we use the same workaround.
811 template <typename T, typename SFINAE = void> struct is_copy_assignable : std::is_copy_assignable<T> {};
812 template <typename Container> struct is_copy_assignable<Container, enable_if_t<all_of<
813 std::is_copy_assignable<Container>,
814 std::is_same<typename Container::value_type &, typename Container::reference>
815 >::value>> : is_copy_assignable<typename Container::value_type> {};
816 template <typename T1, typename T2> struct is_copy_assignable<std::pair<T1, T2>>
817 : all_of<is_copy_assignable<T1>, is_copy_assignable<T2>> {};
819 NAMESPACE_END(detail)
821 // polymorphic_type_hook<itype>::get(src, tinfo) determines whether the object pointed
822 // to by `src` actually is an instance of some class derived from `itype`.
823 // If so, it sets `tinfo` to point to the std::type_info representing that derived
824 // type, and returns a pointer to the start of the most-derived object of that type
825 // (in which `src` is a subobject; this will be the same address as `src` in most
826 // single inheritance cases). If not, or if `src` is nullptr, it simply returns `src`
827 // and leaves `tinfo` at its default value of nullptr.
829 // The default polymorphic_type_hook just returns src. A specialization for polymorphic
830 // types determines the runtime type of the passed object and adjusts the this-pointer
831 // appropriately via dynamic_cast<void*>. This is what enables a C++ Animal* to appear
832 // to Python as a Dog (if Dog inherits from Animal, Animal is polymorphic, Dog is
833 // registered with pybind11, and this Animal is in fact a Dog).
835 // You may specialize polymorphic_type_hook yourself for types that want to appear
836 // polymorphic to Python but do not use C++ RTTI. (This is a not uncommon pattern
837 // in performance-sensitive applications, used most notably in LLVM.)
838 template <typename itype, typename SFINAE = void>
839 struct polymorphic_type_hook
841 static const void *get(const itype *src, const std::type_info*&) { return src; }
843 template <typename itype>
844 struct polymorphic_type_hook<itype, detail::enable_if_t<std::is_polymorphic<itype>::value>>
846 static const void *get(const itype *src, const std::type_info*& type) {
847 type = src ? &typeid(*src) : nullptr;
848 return dynamic_cast<const void*>(src);
852 NAMESPACE_BEGIN(detail)
854 /// Generic type caster for objects stored on the heap
855 template <typename type> class type_caster_base : public type_caster_generic {
856 using itype = intrinsic_t<type>;
859 static constexpr auto name = _<type>();
861 type_caster_base() : type_caster_base(typeid(type)) { }
862 explicit type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
864 static handle cast(const itype &src, return_value_policy policy, handle parent) {
865 if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
866 policy = return_value_policy::copy;
867 return cast(&src, policy, parent);
870 static handle cast(itype &&src, return_value_policy, handle parent) {
871 return cast(&src, return_value_policy::move, parent);
874 // Returns a (pointer, type_info) pair taking care of necessary type lookup for a
875 // polymorphic type (using RTTI by default, but can be overridden by specializing
876 // polymorphic_type_hook). If the instance isn't derived, returns the base version.
877 static std::pair<const void *, const type_info *> src_and_type(const itype *src) {
878 auto &cast_type = typeid(itype);
879 const std::type_info *instance_type = nullptr;
880 const void *vsrc = polymorphic_type_hook<itype>::get(src, instance_type);
881 if (instance_type && !same_type(cast_type, *instance_type)) {
882 // This is a base pointer to a derived type. If the derived type is registered
883 // with pybind11, we want to make the full derived object available.
884 // In the typical case where itype is polymorphic, we get the correct
885 // derived pointer (which may be != base pointer) by a dynamic_cast to
886 // most derived type. If itype is not polymorphic, we won't get here
887 // except via a user-provided specialization of polymorphic_type_hook,
888 // and the user has promised that no this-pointer adjustment is
889 // required in that case, so it's OK to use static_cast.
890 if (const auto *tpi = get_type_info(*instance_type))
893 // Otherwise we have either a nullptr, an `itype` pointer, or an unknown derived pointer, so
895 return type_caster_generic::src_and_type(src, cast_type, instance_type);
898 static handle cast(const itype *src, return_value_policy policy, handle parent) {
899 auto st = src_and_type(src);
900 return type_caster_generic::cast(
901 st.first, policy, parent, st.second,
902 make_copy_constructor(src), make_move_constructor(src));
905 static handle cast_holder(const itype *src, const void *holder) {
906 auto st = src_and_type(src);
907 return type_caster_generic::cast(
908 st.first, return_value_policy::take_ownership, {}, st.second,
909 nullptr, nullptr, holder);
912 template <typename T> using cast_op_type = detail::cast_op_type<T>;
914 operator itype*() { return (type *) value; }
915 operator itype&() { if (!value) throw reference_cast_error(); return *((itype *) value); }
918 using Constructor = void *(*)(const void *);
920 /* Only enabled when the types are {copy,move}-constructible *and* when the type
921 does not have a private operator new implementation. */
922 template <typename T, typename = enable_if_t<is_copy_constructible<T>::value>>
923 static auto make_copy_constructor(const T *x) -> decltype(new T(*x), Constructor{}) {
924 return [](const void *arg) -> void * {
925 return new T(*reinterpret_cast<const T *>(arg));
929 template <typename T, typename = enable_if_t<std::is_move_constructible<T>::value>>
930 static auto make_move_constructor(const T *x) -> decltype(new T(std::move(*const_cast<T *>(x))), Constructor{}) {
931 return [](const void *arg) -> void * {
932 return new T(std::move(*const_cast<T *>(reinterpret_cast<const T *>(arg))));
936 static Constructor make_copy_constructor(...) { return nullptr; }
937 static Constructor make_move_constructor(...) { return nullptr; }
940 template <typename type, typename SFINAE = void> class type_caster : public type_caster_base<type> { };
941 template <typename type> using make_caster = type_caster<intrinsic_t<type>>;
943 // Shortcut for calling a caster's `cast_op_type` cast operator for casting a type_caster to a T
944 template <typename T> typename make_caster<T>::template cast_op_type<T> cast_op(make_caster<T> &caster) {
945 return caster.operator typename make_caster<T>::template cast_op_type<T>();
947 template <typename T> typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>
948 cast_op(make_caster<T> &&caster) {
949 return std::move(caster).operator
950 typename make_caster<T>::template cast_op_type<typename std::add_rvalue_reference<T>::type>();
953 template <typename type> class type_caster<std::reference_wrapper<type>> {
955 using caster_t = make_caster<type>;
957 using subcaster_cast_op_type = typename caster_t::template cast_op_type<type>;
958 static_assert(std::is_same<typename std::remove_const<type>::type &, subcaster_cast_op_type>::value,
959 "std::reference_wrapper<T> caster requires T to have a caster with an `T &` operator");
961 bool load(handle src, bool convert) { return subcaster.load(src, convert); }
962 static constexpr auto name = caster_t::name;
963 static handle cast(const std::reference_wrapper<type> &src, return_value_policy policy, handle parent) {
964 // It is definitely wrong to take ownership of this pointer, so mask that rvp
965 if (policy == return_value_policy::take_ownership || policy == return_value_policy::automatic)
966 policy = return_value_policy::automatic_reference;
967 return caster_t::cast(&src.get(), policy, parent);
969 template <typename T> using cast_op_type = std::reference_wrapper<type>;
970 operator std::reference_wrapper<type>() { return subcaster.operator subcaster_cast_op_type&(); }
973 #define PYBIND11_TYPE_CASTER(type, py_name) \
977 static constexpr auto name = py_name; \
978 template <typename T_, enable_if_t<std::is_same<type, remove_cv_t<T_>>::value, int> = 0> \
979 static handle cast(T_ *src, return_value_policy policy, handle parent) { \
980 if (!src) return none().release(); \
981 if (policy == return_value_policy::take_ownership) { \
982 auto h = cast(std::move(*src), policy, parent); delete src; return h; \
984 return cast(*src, policy, parent); \
987 operator type*() { return &value; } \
988 operator type&() { return value; } \
989 operator type&&() && { return std::move(value); } \
990 template <typename T_> using cast_op_type = pybind11::detail::movable_cast_op_type<T_>
993 template <typename CharT> using is_std_char_type = any_of<
994 std::is_same<CharT, char>, /* std::string */
995 #if defined(PYBIND11_HAS_U8STRING)
996 std::is_same<CharT, char8_t>, /* std::u8string */
998 std::is_same<CharT, char16_t>, /* std::u16string */
999 std::is_same<CharT, char32_t>, /* std::u32string */
1000 std::is_same<CharT, wchar_t> /* std::wstring */
1003 template <typename T>
1004 struct type_caster<T, enable_if_t<std::is_arithmetic<T>::value && !is_std_char_type<T>::value>> {
1005 using _py_type_0 = conditional_t<sizeof(T) <= sizeof(long), long, long long>;
1006 using _py_type_1 = conditional_t<std::is_signed<T>::value, _py_type_0, typename std::make_unsigned<_py_type_0>::type>;
1007 using py_type = conditional_t<std::is_floating_point<T>::value, double, _py_type_1>;
1010 bool load(handle src, bool convert) {
1016 if (std::is_floating_point<T>::value) {
1017 if (convert || PyFloat_Check(src.ptr()))
1018 py_value = (py_type) PyFloat_AsDouble(src.ptr());
1021 } else if (PyFloat_Check(src.ptr())) {
1023 } else if (std::is_unsigned<py_type>::value) {
1024 py_value = as_unsigned<py_type>(src.ptr());
1025 } else { // signed integer:
1026 py_value = sizeof(T) <= sizeof(long)
1027 ? (py_type) PyLong_AsLong(src.ptr())
1028 : (py_type) PYBIND11_LONG_AS_LONGLONG(src.ptr());
1031 bool py_err = py_value == (py_type) -1 && PyErr_Occurred();
1033 // Protect std::numeric_limits::min/max with parentheses
1034 if (py_err || (std::is_integral<T>::value && sizeof(py_type) != sizeof(T) &&
1035 (py_value < (py_type) (std::numeric_limits<T>::min)() ||
1036 py_value > (py_type) (std::numeric_limits<T>::max)()))) {
1037 bool type_error = py_err && PyErr_ExceptionMatches(
1038 #if PY_VERSION_HEX < 0x03000000 && !defined(PYPY_VERSION)
1045 if (type_error && convert && PyNumber_Check(src.ptr())) {
1046 auto tmp = reinterpret_steal<object>(std::is_floating_point<T>::value
1047 ? PyNumber_Float(src.ptr())
1048 : PyNumber_Long(src.ptr()));
1050 return load(tmp, false);
1055 value = (T) py_value;
1059 template<typename U = T>
1060 static typename std::enable_if<std::is_floating_point<U>::value, handle>::type
1061 cast(U src, return_value_policy /* policy */, handle /* parent */) {
1062 return PyFloat_FromDouble((double) src);
1065 template<typename U = T>
1066 static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) <= sizeof(long)), handle>::type
1067 cast(U src, return_value_policy /* policy */, handle /* parent */) {
1068 return PYBIND11_LONG_FROM_SIGNED((long) src);
1071 template<typename U = T>
1072 static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) <= sizeof(unsigned long)), handle>::type
1073 cast(U src, return_value_policy /* policy */, handle /* parent */) {
1074 return PYBIND11_LONG_FROM_UNSIGNED((unsigned long) src);
1077 template<typename U = T>
1078 static typename std::enable_if<!std::is_floating_point<U>::value && std::is_signed<U>::value && (sizeof(U) > sizeof(long)), handle>::type
1079 cast(U src, return_value_policy /* policy */, handle /* parent */) {
1080 return PyLong_FromLongLong((long long) src);
1083 template<typename U = T>
1084 static typename std::enable_if<!std::is_floating_point<U>::value && std::is_unsigned<U>::value && (sizeof(U) > sizeof(unsigned long)), handle>::type
1085 cast(U src, return_value_policy /* policy */, handle /* parent */) {
1086 return PyLong_FromUnsignedLongLong((unsigned long long) src);
1089 PYBIND11_TYPE_CASTER(T, _<std::is_integral<T>::value>("int", "float"));
1092 template<typename T> struct void_caster {
1094 bool load(handle src, bool) {
1095 if (src && src.is_none())
1099 static handle cast(T, return_value_policy /* policy */, handle /* parent */) {
1100 return none().inc_ref();
1102 PYBIND11_TYPE_CASTER(T, _("None"));
1105 template <> class type_caster<void_type> : public void_caster<void_type> {};
1107 template <> class type_caster<void> : public type_caster<void_type> {
1109 using type_caster<void_type>::cast;
1111 bool load(handle h, bool) {
1114 } else if (h.is_none()) {
1119 /* Check if this is a capsule */
1120 if (isinstance<capsule>(h)) {
1121 value = reinterpret_borrow<capsule>(h);
1125 /* Check if this is a C++ type */
1126 auto &bases = all_type_info((PyTypeObject *) h.get_type().ptr());
1127 if (bases.size() == 1) { // Only allowing loading from a single-value type
1128 value = values_and_holders(reinterpret_cast<instance *>(h.ptr())).begin()->value_ptr();
1136 static handle cast(const void *ptr, return_value_policy /* policy */, handle /* parent */) {
1138 return capsule(ptr).release();
1140 return none().inc_ref();
1143 template <typename T> using cast_op_type = void*&;
1144 operator void *&() { return value; }
1145 static constexpr auto name = _("capsule");
1147 void *value = nullptr;
1150 template <> class type_caster<std::nullptr_t> : public void_caster<std::nullptr_t> { };
1152 template <> class type_caster<bool> {
1154 bool load(handle src, bool convert) {
1155 if (!src) return false;
1156 else if (src.ptr() == Py_True) { value = true; return true; }
1157 else if (src.ptr() == Py_False) { value = false; return true; }
1158 else if (convert || !strcmp("numpy.bool_", Py_TYPE(src.ptr())->tp_name)) {
1159 // (allow non-implicit conversion for numpy booleans)
1161 Py_ssize_t res = -1;
1162 if (src.is_none()) {
1163 res = 0; // None is implicitly converted to False
1165 #if defined(PYPY_VERSION)
1166 // On PyPy, check that "__bool__" (or "__nonzero__" on Python 2.7) attr exists
1167 else if (hasattr(src, PYBIND11_BOOL_ATTR)) {
1168 res = PyObject_IsTrue(src.ptr());
1171 // Alternate approach for CPython: this does the same as the above, but optimized
1172 // using the CPython API so as to avoid an unneeded attribute lookup.
1173 else if (auto tp_as_number = src.ptr()->ob_type->tp_as_number) {
1174 if (PYBIND11_NB_BOOL(tp_as_number)) {
1175 res = (*PYBIND11_NB_BOOL(tp_as_number))(src.ptr());
1179 if (res == 0 || res == 1) {
1188 static handle cast(bool src, return_value_policy /* policy */, handle /* parent */) {
1189 return handle(src ? Py_True : Py_False).inc_ref();
1191 PYBIND11_TYPE_CASTER(bool, _("bool"));
1194 // Helper class for UTF-{8,16,32} C++ stl strings:
1195 template <typename StringType, bool IsView = false> struct string_caster {
1196 using CharT = typename StringType::value_type;
1198 // Simplify life by being able to assume standard char sizes (the standard only guarantees
1199 // minimums, but Python requires exact sizes)
1200 static_assert(!std::is_same<CharT, char>::value || sizeof(CharT) == 1, "Unsupported char size != 1");
1201 #if defined(PYBIND11_HAS_U8STRING)
1202 static_assert(!std::is_same<CharT, char8_t>::value || sizeof(CharT) == 1, "Unsupported char8_t size != 1");
1204 static_assert(!std::is_same<CharT, char16_t>::value || sizeof(CharT) == 2, "Unsupported char16_t size != 2");
1205 static_assert(!std::is_same<CharT, char32_t>::value || sizeof(CharT) == 4, "Unsupported char32_t size != 4");
1206 // wchar_t can be either 16 bits (Windows) or 32 (everywhere else)
1207 static_assert(!std::is_same<CharT, wchar_t>::value || sizeof(CharT) == 2 || sizeof(CharT) == 4,
1208 "Unsupported wchar_t size != 2/4");
1209 static constexpr size_t UTF_N = 8 * sizeof(CharT);
1211 bool load(handle src, bool) {
1212 #if PY_MAJOR_VERSION < 3
1215 handle load_src = src;
1218 } else if (!PyUnicode_Check(load_src.ptr())) {
1219 #if PY_MAJOR_VERSION >= 3
1220 return load_bytes(load_src);
1222 if (std::is_same<CharT, char>::value) {
1223 return load_bytes(load_src);
1226 // The below is a guaranteed failure in Python 3 when PyUnicode_Check returns false
1227 if (!PYBIND11_BYTES_CHECK(load_src.ptr()))
1230 temp = reinterpret_steal<object>(PyUnicode_FromObject(load_src.ptr()));
1231 if (!temp) { PyErr_Clear(); return false; }
1236 object utfNbytes = reinterpret_steal<object>(PyUnicode_AsEncodedString(
1237 load_src.ptr(), UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr));
1238 if (!utfNbytes) { PyErr_Clear(); return false; }
1240 const CharT *buffer = reinterpret_cast<const CharT *>(PYBIND11_BYTES_AS_STRING(utfNbytes.ptr()));
1241 size_t length = (size_t) PYBIND11_BYTES_SIZE(utfNbytes.ptr()) / sizeof(CharT);
1242 if (UTF_N > 8) { buffer++; length--; } // Skip BOM for UTF-16/32
1243 value = StringType(buffer, length);
1245 // If we're loading a string_view we need to keep the encoded Python object alive:
1247 loader_life_support::add_patient(utfNbytes);
1252 static handle cast(const StringType &src, return_value_policy /* policy */, handle /* parent */) {
1253 const char *buffer = reinterpret_cast<const char *>(src.data());
1254 ssize_t nbytes = ssize_t(src.size() * sizeof(CharT));
1255 handle s = decode_utfN(buffer, nbytes);
1256 if (!s) throw error_already_set();
1260 PYBIND11_TYPE_CASTER(StringType, _(PYBIND11_STRING_NAME));
1263 static handle decode_utfN(const char *buffer, ssize_t nbytes) {
1264 #if !defined(PYPY_VERSION)
1266 UTF_N == 8 ? PyUnicode_DecodeUTF8(buffer, nbytes, nullptr) :
1267 UTF_N == 16 ? PyUnicode_DecodeUTF16(buffer, nbytes, nullptr, nullptr) :
1268 PyUnicode_DecodeUTF32(buffer, nbytes, nullptr, nullptr);
1270 // PyPy seems to have multiple problems related to PyUnicode_UTF*: the UTF8 version
1271 // sometimes segfaults for unknown reasons, while the UTF16 and 32 versions require a
1272 // non-const char * arguments, which is also a nuisance, so bypass the whole thing by just
1273 // passing the encoding as a string value, which works properly:
1274 return PyUnicode_Decode(buffer, nbytes, UTF_N == 8 ? "utf-8" : UTF_N == 16 ? "utf-16" : "utf-32", nullptr);
1278 // When loading into a std::string or char*, accept a bytes object as-is (i.e.
1279 // without any encoding/decoding attempt). For other C++ char sizes this is a no-op.
1280 // which supports loading a unicode from a str, doesn't take this path.
1281 template <typename C = CharT>
1282 bool load_bytes(enable_if_t<std::is_same<C, char>::value, handle> src) {
1283 if (PYBIND11_BYTES_CHECK(src.ptr())) {
1284 // We were passed a Python 3 raw bytes; accept it into a std::string or char*
1285 // without any encoding attempt.
1286 const char *bytes = PYBIND11_BYTES_AS_STRING(src.ptr());
1288 value = StringType(bytes, (size_t) PYBIND11_BYTES_SIZE(src.ptr()));
1296 template <typename C = CharT>
1297 bool load_bytes(enable_if_t<!std::is_same<C, char>::value, handle>) { return false; }
1300 template <typename CharT, class Traits, class Allocator>
1301 struct type_caster<std::basic_string<CharT, Traits, Allocator>, enable_if_t<is_std_char_type<CharT>::value>>
1302 : string_caster<std::basic_string<CharT, Traits, Allocator>> {};
1304 #ifdef PYBIND11_HAS_STRING_VIEW
1305 template <typename CharT, class Traits>
1306 struct type_caster<std::basic_string_view<CharT, Traits>, enable_if_t<is_std_char_type<CharT>::value>>
1307 : string_caster<std::basic_string_view<CharT, Traits>, true> {};
1310 // Type caster for C-style strings. We basically use a std::string type caster, but also add the
1311 // ability to use None as a nullptr char* (which the string caster doesn't allow).
1312 template <typename CharT> struct type_caster<CharT, enable_if_t<is_std_char_type<CharT>::value>> {
1313 using StringType = std::basic_string<CharT>;
1314 using StringCaster = type_caster<StringType>;
1315 StringCaster str_caster;
1319 bool load(handle src, bool convert) {
1320 if (!src) return false;
1321 if (src.is_none()) {
1322 // Defer accepting None to other overloads (if we aren't in convert mode):
1323 if (!convert) return false;
1327 return str_caster.load(src, convert);
1330 static handle cast(const CharT *src, return_value_policy policy, handle parent) {
1331 if (src == nullptr) return pybind11::none().inc_ref();
1332 return StringCaster::cast(StringType(src), policy, parent);
1335 static handle cast(CharT src, return_value_policy policy, handle parent) {
1336 if (std::is_same<char, CharT>::value) {
1337 handle s = PyUnicode_DecodeLatin1((const char *) &src, 1, nullptr);
1338 if (!s) throw error_already_set();
1341 return StringCaster::cast(StringType(1, src), policy, parent);
1344 operator CharT*() { return none ? nullptr : const_cast<CharT *>(static_cast<StringType &>(str_caster).c_str()); }
1347 throw value_error("Cannot convert None to a character");
1349 auto &value = static_cast<StringType &>(str_caster);
1350 size_t str_len = value.size();
1352 throw value_error("Cannot convert empty string to a character");
1354 // If we're in UTF-8 mode, we have two possible failures: one for a unicode character that
1355 // is too high, and one for multiple unicode characters (caught later), so we need to figure
1356 // out how long the first encoded character is in bytes to distinguish between these two
1357 // errors. We also allow want to allow unicode characters U+0080 through U+00FF, as those
1358 // can fit into a single char value.
1359 if (StringCaster::UTF_N == 8 && str_len > 1 && str_len <= 4) {
1360 unsigned char v0 = static_cast<unsigned char>(value[0]);
1361 size_t char0_bytes = !(v0 & 0x80) ? 1 : // low bits only: 0-127
1362 (v0 & 0xE0) == 0xC0 ? 2 : // 0b110xxxxx - start of 2-byte sequence
1363 (v0 & 0xF0) == 0xE0 ? 3 : // 0b1110xxxx - start of 3-byte sequence
1364 4; // 0b11110xxx - start of 4-byte sequence
1366 if (char0_bytes == str_len) {
1367 // If we have a 128-255 value, we can decode it into a single char:
1368 if (char0_bytes == 2 && (v0 & 0xFC) == 0xC0) { // 0x110000xx 0x10xxxxxx
1369 one_char = static_cast<CharT>(((v0 & 3) << 6) + (static_cast<unsigned char>(value[1]) & 0x3F));
1372 // Otherwise we have a single character, but it's > U+00FF
1373 throw value_error("Character code point not in range(0x100)");
1377 // UTF-16 is much easier: we can only have a surrogate pair for values above U+FFFF, thus a
1378 // surrogate pair with total length 2 instantly indicates a range error (but not a "your
1379 // string was too long" error).
1380 else if (StringCaster::UTF_N == 16 && str_len == 2) {
1381 one_char = static_cast<CharT>(value[0]);
1382 if (one_char >= 0xD800 && one_char < 0xE000)
1383 throw value_error("Character code point not in range(0x10000)");
1387 throw value_error("Expected a character, but multi-character string found");
1389 one_char = value[0];
1393 static constexpr auto name = _(PYBIND11_STRING_NAME);
1394 template <typename _T> using cast_op_type = pybind11::detail::cast_op_type<_T>;
1397 // Base implementation for std::tuple and std::pair
1398 template <template<typename...> class Tuple, typename... Ts> class tuple_caster {
1399 using type = Tuple<Ts...>;
1400 static constexpr auto size = sizeof...(Ts);
1401 using indices = make_index_sequence<size>;
1404 bool load(handle src, bool convert) {
1405 if (!isinstance<sequence>(src))
1407 const auto seq = reinterpret_borrow<sequence>(src);
1408 if (seq.size() != size)
1410 return load_impl(seq, convert, indices{});
1413 template <typename T>
1414 static handle cast(T &&src, return_value_policy policy, handle parent) {
1415 return cast_impl(std::forward<T>(src), policy, parent, indices{});
1418 static constexpr auto name = _("Tuple[") + concat(make_caster<Ts>::name...) + _("]");
1420 template <typename T> using cast_op_type = type;
1422 operator type() & { return implicit_cast(indices{}); }
1423 operator type() && { return std::move(*this).implicit_cast(indices{}); }
1426 template <size_t... Is>
1427 type implicit_cast(index_sequence<Is...>) & { return type(cast_op<Ts>(std::get<Is>(subcasters))...); }
1428 template <size_t... Is>
1429 type implicit_cast(index_sequence<Is...>) && { return type(cast_op<Ts>(std::move(std::get<Is>(subcasters)))...); }
1431 static constexpr bool load_impl(const sequence &, bool, index_sequence<>) { return true; }
1433 template <size_t... Is>
1434 bool load_impl(const sequence &seq, bool convert, index_sequence<Is...>) {
1435 #ifdef __cpp_fold_expressions
1436 if ((... || !std::get<Is>(subcasters).load(seq[Is], convert)))
1439 for (bool r : {std::get<Is>(subcasters).load(seq[Is], convert)...})
1446 /* Implementation: Convert a C++ tuple into a Python tuple */
1447 template <typename T, size_t... Is>
1448 static handle cast_impl(T &&src, return_value_policy policy, handle parent, index_sequence<Is...>) {
1449 std::array<object, size> entries{{
1450 reinterpret_steal<object>(make_caster<Ts>::cast(std::get<Is>(std::forward<T>(src)), policy, parent))...
1452 for (const auto &entry: entries)
1457 for (auto & entry: entries)
1458 PyTuple_SET_ITEM(result.ptr(), counter++, entry.release().ptr());
1459 return result.release();
1462 Tuple<make_caster<Ts>...> subcasters;
1465 template <typename T1, typename T2> class type_caster<std::pair<T1, T2>>
1466 : public tuple_caster<std::pair, T1, T2> {};
1468 template <typename... Ts> class type_caster<std::tuple<Ts...>>
1469 : public tuple_caster<std::tuple, Ts...> {};
1471 /// Helper class which abstracts away certain actions. Users can provide specializations for
1472 /// custom holders, but it's only necessary if the type has a non-standard interface.
1473 template <typename T>
1474 struct holder_helper {
1475 static auto get(const T &p) -> decltype(p.get()) { return p.get(); }
1478 /// Type caster for holder types like std::shared_ptr, etc.
1479 template <typename type, typename holder_type>
1480 struct copyable_holder_caster : public type_caster_base<type> {
1482 using base = type_caster_base<type>;
1483 static_assert(std::is_base_of<base, type_caster<type>>::value,
1484 "Holder classes are only supported for custom types");
1487 using base::typeinfo;
1490 bool load(handle src, bool convert) {
1491 return base::template load_impl<copyable_holder_caster<type, holder_type>>(src, convert);
1494 explicit operator type*() { return this->value; }
1495 explicit operator type&() { return *(this->value); }
1496 explicit operator holder_type*() { return std::addressof(holder); }
1498 // Workaround for Intel compiler bug
1499 // see pybind11 issue 94
1500 #if defined(__ICC) || defined(__INTEL_COMPILER)
1501 operator holder_type&() { return holder; }
1503 explicit operator holder_type&() { return holder; }
1506 static handle cast(const holder_type &src, return_value_policy, handle) {
1507 const auto *ptr = holder_helper<holder_type>::get(src);
1508 return type_caster_base<type>::cast_holder(ptr, &src);
1512 friend class type_caster_generic;
1513 void check_holder_compat() {
1514 if (typeinfo->default_holder)
1515 throw cast_error("Unable to load a custom holder type from a default-holder instance");
1518 bool load_value(value_and_holder &&v_h) {
1519 if (v_h.holder_constructed()) {
1520 value = v_h.value_ptr();
1521 holder = v_h.template holder<holder_type>();
1524 throw cast_error("Unable to cast from non-held to held instance (T& to Holder<T>) "
1526 "(compile in debug mode for type information)");
1528 "of type '" + type_id<holder_type>() + "''");
1533 template <typename T = holder_type, detail::enable_if_t<!std::is_constructible<T, const T &, type*>::value, int> = 0>
1534 bool try_implicit_casts(handle, bool) { return false; }
1536 template <typename T = holder_type, detail::enable_if_t<std::is_constructible<T, const T &, type*>::value, int> = 0>
1537 bool try_implicit_casts(handle src, bool convert) {
1538 for (auto &cast : typeinfo->implicit_casts) {
1539 copyable_holder_caster sub_caster(*cast.first);
1540 if (sub_caster.load(src, convert)) {
1541 value = cast.second(sub_caster.value);
1542 holder = holder_type(sub_caster.holder, (type *) value);
1549 static bool try_direct_conversions(handle) { return false; }
1555 /// Specialize for the common std::shared_ptr, so users don't need to
1556 template <typename T>
1557 class type_caster<std::shared_ptr<T>> : public copyable_holder_caster<T, std::shared_ptr<T>> { };
1559 template <typename type, typename holder_type>
1560 struct move_only_holder_caster {
1561 static_assert(std::is_base_of<type_caster_base<type>, type_caster<type>>::value,
1562 "Holder classes are only supported for custom types");
1564 static handle cast(holder_type &&src, return_value_policy, handle) {
1565 auto *ptr = holder_helper<holder_type>::get(src);
1566 return type_caster_base<type>::cast_holder(ptr, std::addressof(src));
1568 static constexpr auto name = type_caster_base<type>::name;
1571 template <typename type, typename deleter>
1572 class type_caster<std::unique_ptr<type, deleter>>
1573 : public move_only_holder_caster<type, std::unique_ptr<type, deleter>> { };
1575 template <typename type, typename holder_type>
1576 using type_caster_holder = conditional_t<is_copy_constructible<holder_type>::value,
1577 copyable_holder_caster<type, holder_type>,
1578 move_only_holder_caster<type, holder_type>>;
1580 template <typename T, bool Value = false> struct always_construct_holder { static constexpr bool value = Value; };
1582 /// Create a specialization for custom holder types (silently ignores std::shared_ptr)
1583 #define PYBIND11_DECLARE_HOLDER_TYPE(type, holder_type, ...) \
1584 namespace pybind11 { namespace detail { \
1585 template <typename type> \
1586 struct always_construct_holder<holder_type> : always_construct_holder<void, ##__VA_ARGS__> { }; \
1587 template <typename type> \
1588 class type_caster<holder_type, enable_if_t<!is_shared_ptr<holder_type>::value>> \
1589 : public type_caster_holder<type, holder_type> { }; \
1592 // PYBIND11_DECLARE_HOLDER_TYPE holder types:
1593 template <typename base, typename holder> struct is_holder_type :
1594 std::is_base_of<detail::type_caster_holder<base, holder>, detail::type_caster<holder>> {};
1595 // Specialization for always-supported unique_ptr holders:
1596 template <typename base, typename deleter> struct is_holder_type<base, std::unique_ptr<base, deleter>> :
1599 template <typename T> struct handle_type_name { static constexpr auto name = _<T>(); };
1600 template <> struct handle_type_name<bytes> { static constexpr auto name = _(PYBIND11_BYTES_NAME); };
1601 template <> struct handle_type_name<args> { static constexpr auto name = _("*args"); };
1602 template <> struct handle_type_name<kwargs> { static constexpr auto name = _("**kwargs"); };
1604 template <typename type>
1605 struct pyobject_caster {
1606 template <typename T = type, enable_if_t<std::is_same<T, handle>::value, int> = 0>
1607 bool load(handle src, bool /* convert */) { value = src; return static_cast<bool>(value); }
1609 template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
1610 bool load(handle src, bool /* convert */) {
1611 if (!isinstance<type>(src))
1613 value = reinterpret_borrow<type>(src);
1617 static handle cast(const handle &src, return_value_policy /* policy */, handle /* parent */) {
1618 return src.inc_ref();
1620 PYBIND11_TYPE_CASTER(type, handle_type_name<type>::name);
1623 template <typename T>
1624 class type_caster<T, enable_if_t<is_pyobject<T>::value>> : public pyobject_caster<T> { };
1626 // Our conditions for enabling moving are quite restrictive:
1628 // - T needs to be a non-const, non-pointer, non-reference type
1629 // - type_caster<T>::operator T&() must exist
1630 // - the type must be move constructible (obviously)
1632 // - if the type is non-copy-constructible, the object must be the sole owner of the type (i.e. it
1633 // must have ref_count() == 1)h
1634 // If any of the above are not satisfied, we fall back to copying.
1635 template <typename T> using move_is_plain_type = satisfies_none_of<T,
1636 std::is_void, std::is_pointer, std::is_reference, std::is_const
1638 template <typename T, typename SFINAE = void> struct move_always : std::false_type {};
1639 template <typename T> struct move_always<T, enable_if_t<all_of<
1640 move_is_plain_type<T>,
1641 negation<is_copy_constructible<T>>,
1642 std::is_move_constructible<T>,
1643 std::is_same<decltype(std::declval<make_caster<T>>().operator T&()), T&>
1644 >::value>> : std::true_type {};
1645 template <typename T, typename SFINAE = void> struct move_if_unreferenced : std::false_type {};
1646 template <typename T> struct move_if_unreferenced<T, enable_if_t<all_of<
1647 move_is_plain_type<T>,
1648 negation<move_always<T>>,
1649 std::is_move_constructible<T>,
1650 std::is_same<decltype(std::declval<make_caster<T>>().operator T&()), T&>
1651 >::value>> : std::true_type {};
1652 template <typename T> using move_never = none_of<move_always<T>, move_if_unreferenced<T>>;
1654 // Detect whether returning a `type` from a cast on type's type_caster is going to result in a
1655 // reference or pointer to a local variable of the type_caster. Basically, only
1656 // non-reference/pointer `type`s and reference/pointers from a type_caster_generic are safe;
1657 // everything else returns a reference/pointer to a local variable.
1658 template <typename type> using cast_is_temporary_value_reference = bool_constant<
1659 (std::is_reference<type>::value || std::is_pointer<type>::value) &&
1660 !std::is_base_of<type_caster_generic, make_caster<type>>::value &&
1661 !std::is_same<intrinsic_t<type>, void>::value
1664 // When a value returned from a C++ function is being cast back to Python, we almost always want to
1665 // force `policy = move`, regardless of the return value policy the function/method was declared
1667 template <typename Return, typename SFINAE = void> struct return_value_policy_override {
1668 static return_value_policy policy(return_value_policy p) { return p; }
1671 template <typename Return> struct return_value_policy_override<Return,
1672 detail::enable_if_t<std::is_base_of<type_caster_generic, make_caster<Return>>::value, void>> {
1673 static return_value_policy policy(return_value_policy p) {
1674 return !std::is_lvalue_reference<Return>::value &&
1675 !std::is_pointer<Return>::value
1676 ? return_value_policy::move : p;
1680 // Basic python -> C++ casting; throws if casting fails
1681 template <typename T, typename SFINAE> type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &handle) {
1682 if (!conv.load(handle, true)) {
1684 throw cast_error("Unable to cast Python instance to C++ type (compile in debug mode for details)");
1686 throw cast_error("Unable to cast Python instance of type " +
1687 (std::string) str(handle.get_type()) + " to C++ type '" + type_id<T>() + "'");
1692 // Wrapper around the above that also constructs and returns a type_caster
1693 template <typename T> make_caster<T> load_type(const handle &handle) {
1694 make_caster<T> conv;
1695 load_type(conv, handle);
1699 NAMESPACE_END(detail)
1701 // pytype -> C++ type
1702 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
1703 T cast(const handle &handle) {
1704 using namespace detail;
1705 static_assert(!cast_is_temporary_value_reference<T>::value,
1706 "Unable to cast type to reference: value is local to type caster");
1707 return cast_op<T>(load_type<T>(handle));
1710 // pytype -> pytype (calls converting constructor)
1711 template <typename T, detail::enable_if_t<detail::is_pyobject<T>::value, int> = 0>
1712 T cast(const handle &handle) { return T(reinterpret_borrow<object>(handle)); }
1714 // C++ type -> py::object
1715 template <typename T, detail::enable_if_t<!detail::is_pyobject<T>::value, int> = 0>
1716 object cast(const T &value, return_value_policy policy = return_value_policy::automatic_reference,
1717 handle parent = handle()) {
1718 if (policy == return_value_policy::automatic)
1719 policy = std::is_pointer<T>::value ? return_value_policy::take_ownership : return_value_policy::copy;
1720 else if (policy == return_value_policy::automatic_reference)
1721 policy = std::is_pointer<T>::value ? return_value_policy::reference : return_value_policy::copy;
1722 return reinterpret_steal<object>(detail::make_caster<T>::cast(value, policy, parent));
1725 template <typename T> T handle::cast() const { return pybind11::cast<T>(*this); }
1726 template <> inline void handle::cast() const { return; }
1728 template <typename T>
1729 detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
1730 if (obj.ref_count() > 1)
1732 throw cast_error("Unable to cast Python instance to C++ rvalue: instance has multiple references"
1733 " (compile in debug mode for details)");
1735 throw cast_error("Unable to move from Python " + (std::string) str(obj.get_type()) +
1736 " instance to C++ " + type_id<T>() + " instance: instance has multiple references");
1739 // Move into a temporary and return that, because the reference may be a local value of `conv`
1740 T ret = std::move(detail::load_type<T>(obj).operator T&());
1744 // Calling cast() on an rvalue calls pybind::cast with the object rvalue, which does:
1745 // - If we have to move (because T has no copy constructor), do it. This will fail if the moved
1746 // object has multiple references, but trying to copy will fail to compile.
1747 // - If both movable and copyable, check ref count: if 1, move; otherwise copy
1748 // - Otherwise (not movable), copy.
1749 template <typename T> detail::enable_if_t<detail::move_always<T>::value, T> cast(object &&object) {
1750 return move<T>(std::move(object));
1752 template <typename T> detail::enable_if_t<detail::move_if_unreferenced<T>::value, T> cast(object &&object) {
1753 if (object.ref_count() > 1)
1754 return cast<T>(object);
1756 return move<T>(std::move(object));
1758 template <typename T> detail::enable_if_t<detail::move_never<T>::value, T> cast(object &&object) {
1759 return cast<T>(object);
1762 template <typename T> T object::cast() const & { return pybind11::cast<T>(*this); }
1763 template <typename T> T object::cast() && { return pybind11::cast<T>(std::move(*this)); }
1764 template <> inline void object::cast() const & { return; }
1765 template <> inline void object::cast() && { return; }
1767 NAMESPACE_BEGIN(detail)
1769 // Declared in pytypes.h:
1770 template <typename T, enable_if_t<!is_pyobject<T>::value, int>>
1771 object object_or_cast(T &&o) { return pybind11::cast(std::forward<T>(o)); }
1773 struct overload_unused {}; // Placeholder type for the unneeded (and dead code) static variable in the OVERLOAD_INT macro
1774 template <typename ret_type> using overload_caster_t = conditional_t<
1775 cast_is_temporary_value_reference<ret_type>::value, make_caster<ret_type>, overload_unused>;
1777 // Trampoline use: for reference/pointer types to value-converted values, we do a value cast, then
1778 // store the result in the given variable. For other types, this is a no-op.
1779 template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&o, make_caster<T> &caster) {
1780 return cast_op<T>(load_type(caster, o));
1782 template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_ref(object &&, overload_unused &) {
1783 pybind11_fail("Internal error: cast_ref fallback invoked"); }
1785 // Trampoline use: Having a pybind11::cast with an invalid reference type is going to static_assert, even
1786 // though if it's in dead code, so we provide a "trampoline" to pybind11::cast that only does anything in
1787 // cases where pybind11::cast is valid.
1788 template <typename T> enable_if_t<!cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&o) {
1789 return pybind11::cast<T>(std::move(o)); }
1790 template <typename T> enable_if_t<cast_is_temporary_value_reference<T>::value, T> cast_safe(object &&) {
1791 pybind11_fail("Internal error: cast_safe fallback invoked"); }
1792 template <> inline void cast_safe<void>(object &&) {}
1794 NAMESPACE_END(detail)
1796 template <return_value_policy policy = return_value_policy::automatic_reference>
1797 tuple make_tuple() { return tuple(0); }
1799 template <return_value_policy policy = return_value_policy::automatic_reference,
1800 typename... Args> tuple make_tuple(Args&&... args_) {
1801 constexpr size_t size = sizeof...(Args);
1802 std::array<object, size> args {
1803 { reinterpret_steal<object>(detail::make_caster<Args>::cast(
1804 std::forward<Args>(args_), policy, nullptr))... }
1806 for (size_t i = 0; i < args.size(); i++) {
1809 throw cast_error("make_tuple(): unable to convert arguments to Python object (compile in debug mode for details)");
1811 std::array<std::string, size> argtypes { {type_id<Args>()...} };
1812 throw cast_error("make_tuple(): unable to convert argument of type '" +
1813 argtypes[i] + "' to Python object");
1819 for (auto &arg_value : args)
1820 PyTuple_SET_ITEM(result.ptr(), counter++, arg_value.release().ptr());
1824 /// \ingroup annotations
1825 /// Annotation for arguments
1827 /// Constructs an argument with the name of the argument; if null or omitted, this is a positional argument.
1828 constexpr explicit arg(const char *name = nullptr) : name(name), flag_noconvert(false), flag_none(true) { }
1829 /// Assign a value to this argument
1830 template <typename T> arg_v operator=(T &&value) const;
1831 /// Indicate that the type should not be converted in the type caster
1832 arg &noconvert(bool flag = true) { flag_noconvert = flag; return *this; }
1833 /// Indicates that the argument should/shouldn't allow None (e.g. for nullable pointer args)
1834 arg &none(bool flag = true) { flag_none = flag; return *this; }
1836 const char *name; ///< If non-null, this is a named kwargs argument
1837 bool flag_noconvert : 1; ///< If set, do not allow conversion (requires a supporting type caster!)
1838 bool flag_none : 1; ///< If set (the default), allow None to be passed to this argument
1841 /// \ingroup annotations
1842 /// Annotation for arguments with values
1843 struct arg_v : arg {
1845 template <typename T>
1846 arg_v(arg &&base, T &&x, const char *descr = nullptr)
1848 value(reinterpret_steal<object>(
1849 detail::make_caster<T>::cast(x, return_value_policy::automatic, {})
1852 #if !defined(NDEBUG)
1853 , type(type_id<T>())
1858 /// Direct construction with name, default, and description
1859 template <typename T>
1860 arg_v(const char *name, T &&x, const char *descr = nullptr)
1861 : arg_v(arg(name), std::forward<T>(x), descr) { }
1863 /// Called internally when invoking `py::arg("a") = value`
1864 template <typename T>
1865 arg_v(const arg &base, T &&x, const char *descr = nullptr)
1866 : arg_v(arg(base), std::forward<T>(x), descr) { }
1868 /// Same as `arg::noconvert()`, but returns *this as arg_v&, not arg&
1869 arg_v &noconvert(bool flag = true) { arg::noconvert(flag); return *this; }
1871 /// Same as `arg::nonone()`, but returns *this as arg_v&, not arg&
1872 arg_v &none(bool flag = true) { arg::none(flag); return *this; }
1874 /// The default value
1876 /// The (optional) description of the default value
1878 #if !defined(NDEBUG)
1879 /// The C++ type name of the default value (only available when compiled in debug mode)
1884 template <typename T>
1885 arg_v arg::operator=(T &&value) const { return {std::move(*this), std::forward<T>(value)}; }
1887 /// Alias for backward compatibility -- to be removed in version 2.0
1888 template <typename /*unused*/> using arg_t = arg_v;
1890 inline namespace literals {
1892 String literal version of `arg`
1894 constexpr arg operator"" _a(const char *name, size_t) { return arg(name); }
1897 NAMESPACE_BEGIN(detail)
1899 // forward declaration (definition in attr.h)
1900 struct function_record;
1902 /// Internal data associated with a single function call
1903 struct function_call {
1904 function_call(const function_record &f, handle p); // Implementation in attr.h
1906 /// The function data:
1907 const function_record &func;
1909 /// Arguments passed to the function:
1910 std::vector<handle> args;
1912 /// The `convert` value the arguments should be loaded with
1913 std::vector<bool> args_convert;
1915 /// Extra references for the optional `py::args` and/or `py::kwargs` arguments (which, if
1916 /// present, are also in `args` but without a reference).
1917 object args_ref, kwargs_ref;
1919 /// The parent, if any
1922 /// If this is a call to an initializer, this argument contains `self`
1927 /// Helper class which loads arguments for C++ functions called from Python
1928 template <typename... Args>
1929 class argument_loader {
1930 using indices = make_index_sequence<sizeof...(Args)>;
1932 template <typename Arg> using argument_is_args = std::is_same<intrinsic_t<Arg>, args>;
1933 template <typename Arg> using argument_is_kwargs = std::is_same<intrinsic_t<Arg>, kwargs>;
1934 // Get args/kwargs argument positions relative to the end of the argument list:
1935 static constexpr auto args_pos = constexpr_first<argument_is_args, Args...>() - (int) sizeof...(Args),
1936 kwargs_pos = constexpr_first<argument_is_kwargs, Args...>() - (int) sizeof...(Args);
1938 static constexpr bool args_kwargs_are_last = kwargs_pos >= - 1 && args_pos >= kwargs_pos - 1;
1940 static_assert(args_kwargs_are_last, "py::args/py::kwargs are only permitted as the last argument(s) of a function");
1943 static constexpr bool has_kwargs = kwargs_pos < 0;
1944 static constexpr bool has_args = args_pos < 0;
1946 static constexpr auto arg_names = concat(type_descr(make_caster<Args>::name)...);
1948 bool load_args(function_call &call) {
1949 return load_impl_sequence(call, indices{});
1952 template <typename Return, typename Guard, typename Func>
1953 enable_if_t<!std::is_void<Return>::value, Return> call(Func &&f) && {
1954 return std::move(*this).template call_impl<Return>(std::forward<Func>(f), indices{}, Guard{});
1957 template <typename Return, typename Guard, typename Func>
1958 enable_if_t<std::is_void<Return>::value, void_type> call(Func &&f) && {
1959 std::move(*this).template call_impl<Return>(std::forward<Func>(f), indices{}, Guard{});
1965 static bool load_impl_sequence(function_call &, index_sequence<>) { return true; }
1967 template <size_t... Is>
1968 bool load_impl_sequence(function_call &call, index_sequence<Is...>) {
1969 #ifdef __cpp_fold_expressions
1970 if ((... || !std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])))
1973 for (bool r : {std::get<Is>(argcasters).load(call.args[Is], call.args_convert[Is])...})
1980 template <typename Return, typename Func, size_t... Is, typename Guard>
1981 Return call_impl(Func &&f, index_sequence<Is...>, Guard &&) && {
1982 return std::forward<Func>(f)(cast_op<Args>(std::move(std::get<Is>(argcasters)))...);
1985 std::tuple<make_caster<Args>...> argcasters;
1988 /// Helper class which collects only positional arguments for a Python function call.
1989 /// A fancier version below can collect any argument, but this one is optimal for simple calls.
1990 template <return_value_policy policy>
1991 class simple_collector {
1993 template <typename... Ts>
1994 explicit simple_collector(Ts &&...values)
1995 : m_args(pybind11::make_tuple<policy>(std::forward<Ts>(values)...)) { }
1997 const tuple &args() const & { return m_args; }
1998 dict kwargs() const { return {}; }
2000 tuple args() && { return std::move(m_args); }
2002 /// Call a Python function and pass the collected arguments
2003 object call(PyObject *ptr) const {
2004 PyObject *result = PyObject_CallObject(ptr, m_args.ptr());
2006 throw error_already_set();
2007 return reinterpret_steal<object>(result);
2014 /// Helper class which collects positional, keyword, * and ** arguments for a Python function call
2015 template <return_value_policy policy>
2016 class unpacking_collector {
2018 template <typename... Ts>
2019 explicit unpacking_collector(Ts &&...values) {
2020 // Tuples aren't (easily) resizable so a list is needed for collection,
2021 // but the actual function call strictly requires a tuple.
2022 auto args_list = list();
2023 int _[] = { 0, (process(args_list, std::forward<Ts>(values)), 0)... };
2026 m_args = std::move(args_list);
2029 const tuple &args() const & { return m_args; }
2030 const dict &kwargs() const & { return m_kwargs; }
2032 tuple args() && { return std::move(m_args); }
2033 dict kwargs() && { return std::move(m_kwargs); }
2035 /// Call a Python function and pass the collected arguments
2036 object call(PyObject *ptr) const {
2037 PyObject *result = PyObject_Call(ptr, m_args.ptr(), m_kwargs.ptr());
2039 throw error_already_set();
2040 return reinterpret_steal<object>(result);
2044 template <typename T>
2045 void process(list &args_list, T &&x) {
2046 auto o = reinterpret_steal<object>(detail::make_caster<T>::cast(std::forward<T>(x), policy, {}));
2049 argument_cast_error();
2051 argument_cast_error(std::to_string(args_list.size()), type_id<T>());
2054 args_list.append(o);
2057 void process(list &args_list, detail::args_proxy ap) {
2058 for (const auto &a : ap)
2059 args_list.append(a);
2062 void process(list &/*args_list*/, arg_v a) {
2065 nameless_argument_error();
2067 nameless_argument_error(a.type);
2070 if (m_kwargs.contains(a.name)) {
2072 multiple_values_error();
2074 multiple_values_error(a.name);
2079 argument_cast_error();
2081 argument_cast_error(a.name, a.type);
2084 m_kwargs[a.name] = a.value;
2087 void process(list &/*args_list*/, detail::kwargs_proxy kp) {
2090 for (const auto &k : reinterpret_borrow<dict>(kp)) {
2091 if (m_kwargs.contains(k.first)) {
2093 multiple_values_error();
2095 multiple_values_error(str(k.first));
2098 m_kwargs[k.first] = k.second;
2102 [[noreturn]] static void nameless_argument_error() {
2103 throw type_error("Got kwargs without a name; only named arguments "
2104 "may be passed via py::arg() to a python function call. "
2105 "(compile in debug mode for details)");
2107 [[noreturn]] static void nameless_argument_error(std::string type) {
2108 throw type_error("Got kwargs without a name of type '" + type + "'; only named "
2109 "arguments may be passed via py::arg() to a python function call. ");
2111 [[noreturn]] static void multiple_values_error() {
2112 throw type_error("Got multiple values for keyword argument "
2113 "(compile in debug mode for details)");
2116 [[noreturn]] static void multiple_values_error(std::string name) {
2117 throw type_error("Got multiple values for keyword argument '" + name + "'");
2120 [[noreturn]] static void argument_cast_error() {
2121 throw cast_error("Unable to convert call argument to Python object "
2122 "(compile in debug mode for details)");
2125 [[noreturn]] static void argument_cast_error(std::string name, std::string type) {
2126 throw cast_error("Unable to convert call argument '" + name
2127 + "' of type '" + type + "' to Python object");
2135 /// Collect only positional arguments for a Python function call
2136 template <return_value_policy policy, typename... Args,
2137 typename = enable_if_t<all_of<is_positional<Args>...>::value>>
2138 simple_collector<policy> collect_arguments(Args &&...args) {
2139 return simple_collector<policy>(std::forward<Args>(args)...);
2142 /// Collect all arguments, including keywords and unpacking (only instantiated when needed)
2143 template <return_value_policy policy, typename... Args,
2144 typename = enable_if_t<!all_of<is_positional<Args>...>::value>>
2145 unpacking_collector<policy> collect_arguments(Args &&...args) {
2146 // Following argument order rules for generalized unpacking according to PEP 448
2148 constexpr_last<is_positional, Args...>() < constexpr_first<is_keyword_or_ds, Args...>()
2149 && constexpr_last<is_s_unpacking, Args...>() < constexpr_first<is_ds_unpacking, Args...>(),
2150 "Invalid function call: positional args must precede keywords and ** unpacking; "
2151 "* unpacking must precede ** unpacking"
2153 return unpacking_collector<policy>(std::forward<Args>(args)...);
2156 template <typename Derived>
2157 template <return_value_policy policy, typename... Args>
2158 object object_api<Derived>::operator()(Args &&...args) const {
2159 return detail::collect_arguments<policy>(std::forward<Args>(args)...).call(derived().ptr());
2162 template <typename Derived>
2163 template <return_value_policy policy, typename... Args>
2164 object object_api<Derived>::call(Args &&...args) const {
2165 return operator()<policy>(std::forward<Args>(args)...);
2168 NAMESPACE_END(detail)
2170 #define PYBIND11_MAKE_OPAQUE(...) \
2171 namespace pybind11 { namespace detail { \
2172 template<> class type_caster<__VA_ARGS__> : public type_caster_base<__VA_ARGS__> { }; \
2175 /// Lets you pass a type containing a `,` through a macro parameter without needing a separate
2176 /// typedef, e.g.: `PYBIND11_OVERLOAD(PYBIND11_TYPE(ReturnType<A, B>), PYBIND11_TYPE(Parent<C, D>), f, arg)`
2177 #define PYBIND11_TYPE(...) __VA_ARGS__
2179 NAMESPACE_END(PYBIND11_NAMESPACE)