2 pybind11/detail/common.h -- Basic macros
4 Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>
6 All rights reserved. Use of this source code is governed by a
7 BSD-style license that can be found in the LICENSE file.
12 #if !defined(NAMESPACE_BEGIN)
13 # define NAMESPACE_BEGIN(name) namespace name {
15 #if !defined(NAMESPACE_END)
16 # define NAMESPACE_END(name) }
19 // Robust support for some features and loading modules compiled against different pybind versions
20 // requires forcing hidden visibility on pybind code, so we enforce this by setting the attribute on
21 // the main `pybind11` namespace.
22 #if !defined(PYBIND11_NAMESPACE)
24 # define PYBIND11_NAMESPACE pybind11 __attribute__((visibility("hidden")))
26 # define PYBIND11_NAMESPACE pybind11
30 #if !(defined(_MSC_VER) && __cplusplus == 199711L) && !defined(__INTEL_COMPILER)
31 # if __cplusplus >= 201402L
32 # define PYBIND11_CPP14
33 # if __cplusplus >= 201703L
34 # define PYBIND11_CPP17
37 #elif defined(_MSC_VER) && __cplusplus == 199711L
38 // MSVC sets _MSVC_LANG rather than __cplusplus (supposedly until the standard is fully implemented)
39 // Unless you use the /Zc:__cplusplus flag on Visual Studio 2017 15.7 Preview 3 or newer
40 # if _MSVC_LANG >= 201402L
41 # define PYBIND11_CPP14
42 # if _MSVC_LANG > 201402L && _MSC_VER >= 1910
43 # define PYBIND11_CPP17
48 // Compiler version assertions
49 #if defined(__INTEL_COMPILER)
50 # if __INTEL_COMPILER < 1700
51 # error pybind11 requires Intel C++ compiler v17 or newer
53 #elif defined(__clang__) && !defined(__apple_build_version__)
54 # if __clang_major__ < 3 || (__clang_major__ == 3 && __clang_minor__ < 3)
55 # error pybind11 requires clang 3.3 or newer
57 #elif defined(__clang__)
58 // Apple changes clang version macros to its Xcode version; the first Xcode release based on
59 // (upstream) clang 3.3 was Xcode 5:
60 # if __clang_major__ < 5
61 # error pybind11 requires Xcode/clang 5.0 or newer
63 #elif defined(__GNUG__)
64 # if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 8)
65 # error pybind11 requires gcc 4.8 or newer
67 #elif defined(_MSC_VER)
68 // Pybind hits various compiler bugs in 2015u2 and earlier, and also makes use of some stl features
69 // (e.g. std::negation) added in 2015u3:
70 # if _MSC_FULL_VER < 190024210
71 # error pybind11 requires MSVC 2015 update 3 or newer
75 #if !defined(PYBIND11_EXPORT)
76 # if defined(WIN32) || defined(_WIN32)
77 # define PYBIND11_EXPORT __declspec(dllexport)
79 # define PYBIND11_EXPORT __attribute__ ((visibility("default")))
84 # define PYBIND11_NOINLINE __declspec(noinline)
86 # define PYBIND11_NOINLINE __attribute__ ((noinline))
89 #if defined(PYBIND11_CPP14)
90 # define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
92 # define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
95 #define PYBIND11_VERSION_MAJOR 2
96 #define PYBIND11_VERSION_MINOR 5
97 #define PYBIND11_VERSION_PATCH 0
99 /// Include Python header, disable linking to pythonX_d.lib on Windows in debug mode
100 #if defined(_MSC_VER)
101 # if (PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION < 4)
102 # define HAVE_ROUND 1
104 # pragma warning(push)
105 # pragma warning(disable: 4510 4610 4512 4005)
106 # if defined(_DEBUG) && !defined(Py_DEBUG)
107 # define PYBIND11_DEBUG_MARKER
113 #include <frameobject.h>
114 #include <pythread.h>
116 /* Python #defines overrides on all sorts of core functions, which
117 tends to weak havok in C++ codebases that expect these to work
118 like regular functions (potentially with several overloads) */
129 #if defined(copysign)
133 #if defined(_MSC_VER)
134 # if defined(PYBIND11_DEBUG_MARKER)
136 # undef PYBIND11_DEBUG_MARKER
138 # pragma warning(pop)
143 #include <forward_list>
147 #include <unordered_set>
148 #include <unordered_map>
151 #include <type_traits>
153 #if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
154 #define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
155 #define PYBIND11_INSTANCE_METHOD_CHECK PyInstanceMethod_Check
156 #define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyInstanceMethod_GET_FUNCTION
157 #define PYBIND11_BYTES_CHECK PyBytes_Check
158 #define PYBIND11_BYTES_FROM_STRING PyBytes_FromString
159 #define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyBytes_FromStringAndSize
160 #define PYBIND11_BYTES_AS_STRING_AND_SIZE PyBytes_AsStringAndSize
161 #define PYBIND11_BYTES_AS_STRING PyBytes_AsString
162 #define PYBIND11_BYTES_SIZE PyBytes_Size
163 #define PYBIND11_LONG_CHECK(o) PyLong_Check(o)
164 #define PYBIND11_LONG_AS_LONGLONG(o) PyLong_AsLongLong(o)
165 #define PYBIND11_LONG_FROM_SIGNED(o) PyLong_FromSsize_t((ssize_t) o)
166 #define PYBIND11_LONG_FROM_UNSIGNED(o) PyLong_FromSize_t((size_t) o)
167 #define PYBIND11_BYTES_NAME "bytes"
168 #define PYBIND11_STRING_NAME "str"
169 #define PYBIND11_SLICE_OBJECT PyObject
170 #define PYBIND11_FROM_STRING PyUnicode_FromString
171 #define PYBIND11_STR_TYPE ::pybind11::str
172 #define PYBIND11_BOOL_ATTR "__bool__"
173 #define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_bool)
174 // Providing a separate declaration to make Clang's -Wmissing-prototypes happy
175 #define PYBIND11_PLUGIN_IMPL(name) \
176 extern "C" PYBIND11_EXPORT PyObject *PyInit_##name(); \
177 extern "C" PYBIND11_EXPORT PyObject *PyInit_##name()
180 #define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyMethod_New(ptr, nullptr, class_)
181 #define PYBIND11_INSTANCE_METHOD_CHECK PyMethod_Check
182 #define PYBIND11_INSTANCE_METHOD_GET_FUNCTION PyMethod_GET_FUNCTION
183 #define PYBIND11_BYTES_CHECK PyString_Check
184 #define PYBIND11_BYTES_FROM_STRING PyString_FromString
185 #define PYBIND11_BYTES_FROM_STRING_AND_SIZE PyString_FromStringAndSize
186 #define PYBIND11_BYTES_AS_STRING_AND_SIZE PyString_AsStringAndSize
187 #define PYBIND11_BYTES_AS_STRING PyString_AsString
188 #define PYBIND11_BYTES_SIZE PyString_Size
189 #define PYBIND11_LONG_CHECK(o) (PyInt_Check(o) || PyLong_Check(o))
190 #define PYBIND11_LONG_AS_LONGLONG(o) (PyInt_Check(o) ? (long long) PyLong_AsLong(o) : PyLong_AsLongLong(o))
191 #define PYBIND11_LONG_FROM_SIGNED(o) PyInt_FromSsize_t((ssize_t) o) // Returns long if needed.
192 #define PYBIND11_LONG_FROM_UNSIGNED(o) PyInt_FromSize_t((size_t) o) // Returns long if needed.
193 #define PYBIND11_BYTES_NAME "str"
194 #define PYBIND11_STRING_NAME "unicode"
195 #define PYBIND11_SLICE_OBJECT PySliceObject
196 #define PYBIND11_FROM_STRING PyString_FromString
197 #define PYBIND11_STR_TYPE ::pybind11::bytes
198 #define PYBIND11_BOOL_ATTR "__nonzero__"
199 #define PYBIND11_NB_BOOL(ptr) ((ptr)->nb_nonzero)
200 // Providing a separate PyInit decl to make Clang's -Wmissing-prototypes happy
201 #define PYBIND11_PLUGIN_IMPL(name) \
202 static PyObject *pybind11_init_wrapper(); \
203 extern "C" PYBIND11_EXPORT void init##name(); \
204 extern "C" PYBIND11_EXPORT void init##name() { \
205 (void)pybind11_init_wrapper(); \
207 PyObject *pybind11_init_wrapper()
210 #if PY_VERSION_HEX >= 0x03050000 && PY_VERSION_HEX < 0x03050200
212 struct _Py_atomic_address { void *value; };
213 PyAPI_DATA(_Py_atomic_address) _PyThreadState_Current;
217 #define PYBIND11_TRY_NEXT_OVERLOAD ((PyObject *) 1) // special failure return code
218 #define PYBIND11_STRINGIFY(x) #x
219 #define PYBIND11_TOSTRING(x) PYBIND11_STRINGIFY(x)
220 #define PYBIND11_CONCAT(first, second) first##second
221 #define PYBIND11_ENSURE_INTERNALS_READY \
222 pybind11::detail::get_internals();
224 #define PYBIND11_CHECK_PYTHON_VERSION \
226 const char *compiled_ver = PYBIND11_TOSTRING(PY_MAJOR_VERSION) \
227 "." PYBIND11_TOSTRING(PY_MINOR_VERSION); \
228 const char *runtime_ver = Py_GetVersion(); \
229 size_t len = std::strlen(compiled_ver); \
230 if (std::strncmp(runtime_ver, compiled_ver, len) != 0 \
231 || (runtime_ver[len] >= '0' && runtime_ver[len] <= '9')) { \
232 PyErr_Format(PyExc_ImportError, \
233 "Python version mismatch: module was compiled for Python %s, " \
234 "but the interpreter version is incompatible: %s.", \
235 compiled_ver, runtime_ver); \
240 #define PYBIND11_CATCH_INIT_EXCEPTIONS \
241 catch (pybind11::error_already_set &e) { \
242 PyErr_SetString(PyExc_ImportError, e.what()); \
244 } catch (const std::exception &e) { \
245 PyErr_SetString(PyExc_ImportError, e.what()); \
250 ***Deprecated in favor of PYBIND11_MODULE***
252 This macro creates the entry point that will be invoked when the Python interpreter
253 imports a plugin library. Please create a `module` in the function body and return
254 the pointer to its underlying Python object at the end.
258 PYBIND11_PLUGIN(example) {
259 pybind11::module m("example", "pybind11 example plugin");
260 /// Set up bindings here
264 #define PYBIND11_PLUGIN(name) \
265 PYBIND11_DEPRECATED("PYBIND11_PLUGIN is deprecated, use PYBIND11_MODULE") \
266 static PyObject *pybind11_init(); \
267 PYBIND11_PLUGIN_IMPL(name) { \
268 PYBIND11_CHECK_PYTHON_VERSION \
269 PYBIND11_ENSURE_INTERNALS_READY \
271 return pybind11_init(); \
272 } PYBIND11_CATCH_INIT_EXCEPTIONS \
274 PyObject *pybind11_init()
277 This macro creates the entry point that will be invoked when the Python interpreter
278 imports an extension module. The module name is given as the fist argument and it
279 should not be in quotes. The second macro argument defines a variable of type
280 `py::module` which can be used to initialize the module.
284 PYBIND11_MODULE(example, m) {
285 m.doc() = "pybind11 example module";
289 return "Hello, World!";
293 #define PYBIND11_MODULE(name, variable) \
294 static void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &); \
295 PYBIND11_PLUGIN_IMPL(name) { \
296 PYBIND11_CHECK_PYTHON_VERSION \
297 PYBIND11_ENSURE_INTERNALS_READY \
298 auto m = pybind11::module(PYBIND11_TOSTRING(name)); \
300 PYBIND11_CONCAT(pybind11_init_, name)(m); \
302 } PYBIND11_CATCH_INIT_EXCEPTIONS \
304 void PYBIND11_CONCAT(pybind11_init_, name)(pybind11::module &variable)
307 NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
309 using ssize_t = Py_ssize_t;
310 using size_t = std::size_t;
312 /// Approach used to cast a previously unknown C++ instance into a Python object
313 enum class return_value_policy : uint8_t {
314 /** This is the default return value policy, which falls back to the policy
315 return_value_policy::take_ownership when the return value is a pointer.
316 Otherwise, it uses return_value::move or return_value::copy for rvalue
317 and lvalue references, respectively. See below for a description of what
318 all of these different policies do. */
321 /** As above, but use policy return_value_policy::reference when the return
322 value is a pointer. This is the default conversion policy for function
323 arguments when calling Python functions manually from C++ code (i.e. via
324 handle::operator()). You probably won't need to use this. */
327 /** Reference an existing object (i.e. do not create a new copy) and take
328 ownership. Python will call the destructor and delete operator when the
329 object’s reference count reaches zero. Undefined behavior ensues when
330 the C++ side does the same.. */
333 /** Create a new copy of the returned object, which will be owned by
334 Python. This policy is comparably safe because the lifetimes of the two
335 instances are decoupled. */
338 /** Use std::move to move the return value contents into a new instance
339 that will be owned by Python. This policy is comparably safe because the
340 lifetimes of the two instances (move source and destination) are
344 /** Reference an existing object, but do not take ownership. The C++ side
345 is responsible for managing the object’s lifetime and deallocating it
346 when it is no longer used. Warning: undefined behavior will ensue when
347 the C++ side deletes an object that is still referenced and used by
351 /** This policy only applies to methods and properties. It references the
352 object without taking ownership similar to the above
353 return_value_policy::reference policy. In contrast to that policy, the
354 function or property’s implicit this argument (called the parent) is
355 considered to be the the owner of the return value (the child).
356 pybind11 then couples the lifetime of the parent to the child via a
357 reference relationship that ensures that the parent cannot be garbage
358 collected while Python is still using the child. More advanced
359 variations of this scheme are also possible using combinations of
360 return_value_policy::reference and the keep_alive call policy */
364 NAMESPACE_BEGIN(detail)
366 inline static constexpr int log2(size_t n, int k = 0) { return (n <= 1) ? k : log2(n >> 1, k + 1); }
368 // Returns the size as a multiple of sizeof(void *), rounded up.
369 inline static constexpr size_t size_in_ptrs(size_t s) { return 1 + ((s - 1) >> log2(sizeof(void *))); }
372 * The space to allocate for simple layout instance holders (see below) in multiple of the size of
373 * a pointer (e.g. 2 means 16 bytes on 64-bit architectures). The default is the minimum required
374 * to holder either a std::unique_ptr or std::shared_ptr (which is almost always
375 * sizeof(std::shared_ptr<T>)).
377 constexpr size_t instance_simple_holder_in_ptrs() {
378 static_assert(sizeof(std::shared_ptr<int>) >= sizeof(std::unique_ptr<int>),
379 "pybind assumes std::shared_ptrs are at least as big as std::unique_ptrs");
380 return size_in_ptrs(sizeof(std::shared_ptr<int>));
383 // Forward declarations
385 struct value_and_holder;
387 struct nonsimple_values_and_holders {
388 void **values_and_holders;
392 /// The 'instance' type which needs to be standard layout (need to be able to use 'offsetof')
395 /// Storage for pointers and holder; see simple_layout, below, for a description
397 void *simple_value_holder[1 + instance_simple_holder_in_ptrs()];
398 nonsimple_values_and_holders nonsimple;
402 /// If true, the pointer is owned which means we're free to manage it with a holder.
405 * An instance has two possible value/holder layouts.
407 * Simple layout (when this flag is true), means the `simple_value_holder` is set with a pointer
408 * and the holder object governing that pointer, i.e. [val1*][holder]. This layout is applied
409 * whenever there is no python-side multiple inheritance of bound C++ types *and* the type's
410 * holder will fit in the default space (which is large enough to hold either a std::unique_ptr
411 * or std::shared_ptr).
413 * Non-simple layout applies when using custom holders that require more space than `shared_ptr`
414 * (which is typically the size of two pointers), or when multiple inheritance is used on the
415 * python side. Non-simple layout allocates the required amount of memory to have multiple
416 * bound C++ classes as parents. Under this layout, `nonsimple.values_and_holders` is set to a
417 * pointer to allocated space of the required space to hold a sequence of value pointers and
418 * holders followed `status`, a set of bit flags (1 byte each), i.e.
419 * [val1*][holder1][val2*][holder2]...[bb...] where each [block] is rounded up to a multiple of
420 * `sizeof(void *)`. `nonsimple.status` is, for convenience, a pointer to the
421 * beginning of the [bb...] block (but not independently allocated).
423 * Status bits indicate whether the associated holder is constructed (&
424 * status_holder_constructed) and whether the value pointer is registered (&
425 * status_instance_registered) in `registered_instances`.
427 bool simple_layout : 1;
428 /// For simple layout, tracks whether the holder has been constructed
429 bool simple_holder_constructed : 1;
430 /// For simple layout, tracks whether the instance is registered in `registered_instances`
431 bool simple_instance_registered : 1;
432 /// If true, get_internals().patients has an entry for this object
433 bool has_patients : 1;
435 /// Initializes all of the above type/values/holders data (but not the instance values themselves)
436 void allocate_layout();
438 /// Destroys/deallocates all of the above
439 void deallocate_layout();
441 /// Returns the value_and_holder wrapper for the given type (or the first, if `find_type`
442 /// omitted). Returns a default-constructed (with `.inst = nullptr`) object on failure if
443 /// `throw_if_missing` is false.
444 value_and_holder get_value_and_holder(const type_info *find_type = nullptr, bool throw_if_missing = true);
446 /// Bit values for the non-simple status flags
447 static constexpr uint8_t status_holder_constructed = 1;
448 static constexpr uint8_t status_instance_registered = 2;
451 static_assert(std::is_standard_layout<instance>::value, "Internal error: `pybind11::detail::instance` is not standard layout!");
453 /// from __cpp_future__ import (convenient aliases from C++14/17)
454 #if defined(PYBIND11_CPP14) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
455 using std::enable_if_t;
456 using std::conditional_t;
457 using std::remove_cv_t;
458 using std::remove_reference_t;
460 template <bool B, typename T = void> using enable_if_t = typename std::enable_if<B, T>::type;
461 template <bool B, typename T, typename F> using conditional_t = typename std::conditional<B, T, F>::type;
462 template <typename T> using remove_cv_t = typename std::remove_cv<T>::type;
463 template <typename T> using remove_reference_t = typename std::remove_reference<T>::type;
467 #if defined(PYBIND11_CPP14)
468 using std::index_sequence;
469 using std::make_index_sequence;
471 template<size_t ...> struct index_sequence { };
472 template<size_t N, size_t ...S> struct make_index_sequence_impl : make_index_sequence_impl <N - 1, N - 1, S...> { };
473 template<size_t ...S> struct make_index_sequence_impl <0, S...> { typedef index_sequence<S...> type; };
474 template<size_t N> using make_index_sequence = typename make_index_sequence_impl<N>::type;
477 /// Make an index sequence of the indices of true arguments
478 template <typename ISeq, size_t, bool...> struct select_indices_impl { using type = ISeq; };
479 template <size_t... IPrev, size_t I, bool B, bool... Bs> struct select_indices_impl<index_sequence<IPrev...>, I, B, Bs...>
480 : select_indices_impl<conditional_t<B, index_sequence<IPrev..., I>, index_sequence<IPrev...>>, I + 1, Bs...> {};
481 template <bool... Bs> using select_indices = typename select_indices_impl<index_sequence<>, 0, Bs...>::type;
483 /// Backports of std::bool_constant and std::negation to accommodate older compilers
484 template <bool B> using bool_constant = std::integral_constant<bool, B>;
485 template <typename T> struct negation : bool_constant<!T::value> { };
487 template <typename...> struct void_t_impl { using type = void; };
488 template <typename... Ts> using void_t = typename void_t_impl<Ts...>::type;
490 /// Compile-time all/any/none of that check the boolean value of all template types
491 #if defined(__cpp_fold_expressions) && !(defined(_MSC_VER) && (_MSC_VER < 1916))
492 template <class... Ts> using all_of = bool_constant<(Ts::value && ...)>;
493 template <class... Ts> using any_of = bool_constant<(Ts::value || ...)>;
494 #elif !defined(_MSC_VER)
495 template <bool...> struct bools {};
496 template <class... Ts> using all_of = std::is_same<
497 bools<Ts::value..., true>,
498 bools<true, Ts::value...>>;
499 template <class... Ts> using any_of = negation<all_of<negation<Ts>...>>;
501 // MSVC has trouble with the above, but supports std::conjunction, which we can use instead (albeit
502 // at a slight loss of compilation efficiency).
503 template <class... Ts> using all_of = std::conjunction<Ts...>;
504 template <class... Ts> using any_of = std::disjunction<Ts...>;
506 template <class... Ts> using none_of = negation<any_of<Ts...>>;
508 template <class T, template<class> class... Predicates> using satisfies_all_of = all_of<Predicates<T>...>;
509 template <class T, template<class> class... Predicates> using satisfies_any_of = any_of<Predicates<T>...>;
510 template <class T, template<class> class... Predicates> using satisfies_none_of = none_of<Predicates<T>...>;
512 /// Strip the class from a method type
513 template <typename T> struct remove_class { };
514 template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...)> { typedef R type(A...); };
515 template <typename C, typename R, typename... A> struct remove_class<R (C::*)(A...) const> { typedef R type(A...); };
517 /// Helper template to strip away type modifiers
518 template <typename T> struct intrinsic_type { typedef T type; };
519 template <typename T> struct intrinsic_type<const T> { typedef typename intrinsic_type<T>::type type; };
520 template <typename T> struct intrinsic_type<T*> { typedef typename intrinsic_type<T>::type type; };
521 template <typename T> struct intrinsic_type<T&> { typedef typename intrinsic_type<T>::type type; };
522 template <typename T> struct intrinsic_type<T&&> { typedef typename intrinsic_type<T>::type type; };
523 template <typename T, size_t N> struct intrinsic_type<const T[N]> { typedef typename intrinsic_type<T>::type type; };
524 template <typename T, size_t N> struct intrinsic_type<T[N]> { typedef typename intrinsic_type<T>::type type; };
525 template <typename T> using intrinsic_t = typename intrinsic_type<T>::type;
527 /// Helper type to replace 'void' in some expressions
528 struct void_type { };
530 /// Helper template which holds a list of types
531 template <typename...> struct type_list { };
533 /// Compile-time integer sum
534 #ifdef __cpp_fold_expressions
535 template <typename... Ts> constexpr size_t constexpr_sum(Ts... ns) { return (0 + ... + size_t{ns}); }
537 constexpr size_t constexpr_sum() { return 0; }
538 template <typename T, typename... Ts>
539 constexpr size_t constexpr_sum(T n, Ts... ns) { return size_t{n} + constexpr_sum(ns...); }
542 NAMESPACE_BEGIN(constexpr_impl)
543 /// Implementation details for constexpr functions
544 constexpr int first(int i) { return i; }
545 template <typename T, typename... Ts>
546 constexpr int first(int i, T v, Ts... vs) { return v ? i : first(i + 1, vs...); }
548 constexpr int last(int /*i*/, int result) { return result; }
549 template <typename T, typename... Ts>
550 constexpr int last(int i, int result, T v, Ts... vs) { return last(i + 1, v ? i : result, vs...); }
551 NAMESPACE_END(constexpr_impl)
553 /// Return the index of the first type in Ts which satisfies Predicate<T>. Returns sizeof...(Ts) if
555 template <template<typename> class Predicate, typename... Ts>
556 constexpr int constexpr_first() { return constexpr_impl::first(0, Predicate<Ts>::value...); }
558 /// Return the index of the last type in Ts which satisfies Predicate<T>, or -1 if none match.
559 template <template<typename> class Predicate, typename... Ts>
560 constexpr int constexpr_last() { return constexpr_impl::last(0, -1, Predicate<Ts>::value...); }
562 /// Return the Nth element from the parameter pack
563 template <size_t N, typename T, typename... Ts>
564 struct pack_element { using type = typename pack_element<N - 1, Ts...>::type; };
565 template <typename T, typename... Ts>
566 struct pack_element<0, T, Ts...> { using type = T; };
568 /// Return the one and only type which matches the predicate, or Default if none match.
569 /// If more than one type matches the predicate, fail at compile-time.
570 template <template<typename> class Predicate, typename Default, typename... Ts>
572 static constexpr auto found = constexpr_sum(Predicate<Ts>::value...);
573 static_assert(found <= 1, "Found more than one type matching the predicate");
575 static constexpr auto index = found ? constexpr_first<Predicate, Ts...>() : 0;
576 using type = conditional_t<found, typename pack_element<index, Ts...>::type, Default>;
578 template <template<typename> class P, typename Default>
579 struct exactly_one<P, Default> { using type = Default; };
581 template <template<typename> class Predicate, typename Default, typename... Ts>
582 using exactly_one_t = typename exactly_one<Predicate, Default, Ts...>::type;
584 /// Defer the evaluation of type T until types Us are instantiated
585 template <typename T, typename... /*Us*/> struct deferred_type { using type = T; };
586 template <typename T, typename... Us> using deferred_t = typename deferred_type<T, Us...>::type;
588 /// Like is_base_of, but requires a strict base (i.e. `is_strict_base_of<T, T>::value == false`,
589 /// unlike `std::is_base_of`)
590 template <typename Base, typename Derived> using is_strict_base_of = bool_constant<
591 std::is_base_of<Base, Derived>::value && !std::is_same<Base, Derived>::value>;
593 /// Like is_base_of, but also requires that the base type is accessible (i.e. that a Derived pointer
594 /// can be converted to a Base pointer)
595 template <typename Base, typename Derived> using is_accessible_base_of = bool_constant<
596 std::is_base_of<Base, Derived>::value && std::is_convertible<Derived *, Base *>::value>;
598 template <template<typename...> class Base>
599 struct is_template_base_of_impl {
600 template <typename... Us> static std::true_type check(Base<Us...> *);
601 static std::false_type check(...);
604 /// Check if a template is the base of a type. For example:
605 /// `is_template_base_of<Base, T>` is true if `struct T : Base<U> {}` where U can be anything
606 template <template<typename...> class Base, typename T>
607 #if !defined(_MSC_VER)
608 using is_template_base_of = decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr));
609 #else // MSVC2015 has trouble with decltype in template aliases
610 struct is_template_base_of : decltype(is_template_base_of_impl<Base>::check((intrinsic_t<T>*)nullptr)) { };
613 /// Check if T is an instantiation of the template `Class`. For example:
614 /// `is_instantiation<shared_ptr, T>` is true if `T == shared_ptr<U>` where U can be anything.
615 template <template<typename...> class Class, typename T>
616 struct is_instantiation : std::false_type { };
617 template <template<typename...> class Class, typename... Us>
618 struct is_instantiation<Class, Class<Us...>> : std::true_type { };
620 /// Check if T is std::shared_ptr<U> where U can be anything
621 template <typename T> using is_shared_ptr = is_instantiation<std::shared_ptr, T>;
623 /// Check if T looks like an input iterator
624 template <typename T, typename = void> struct is_input_iterator : std::false_type {};
625 template <typename T>
626 struct is_input_iterator<T, void_t<decltype(*std::declval<T &>()), decltype(++std::declval<T &>())>>
629 template <typename T> using is_function_pointer = bool_constant<
630 std::is_pointer<T>::value && std::is_function<typename std::remove_pointer<T>::type>::value>;
632 template <typename F> struct strip_function_object {
633 using type = typename remove_class<decltype(&F::operator())>::type;
636 // Extracts the function signature from a function, function pointer or lambda.
637 template <typename Function, typename F = remove_reference_t<Function>>
638 using function_signature_t = conditional_t<
639 std::is_function<F>::value,
641 typename conditional_t<
642 std::is_pointer<F>::value || std::is_member_pointer<F>::value,
643 std::remove_pointer<F>,
644 strip_function_object<F>
648 /// Returns true if the type looks like a lambda: that is, isn't a function, pointer or member
649 /// pointer. Note that this can catch all sorts of other things, too; this is intended to be used
650 /// in a place where passing a lambda makes sense.
651 template <typename T> using is_lambda = satisfies_none_of<remove_reference_t<T>,
652 std::is_function, std::is_pointer, std::is_member_pointer>;
654 /// Ignore that a variable is unused in compiler warnings
655 inline void ignore_unused(const int *) { }
657 /// Apply a function over each element of a parameter pack
658 #ifdef __cpp_fold_expressions
659 #define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
661 using expand_side_effects = bool[];
662 #define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
665 NAMESPACE_END(detail)
667 /// C++ bindings of builtin Python exceptions
668 class builtin_exception : public std::runtime_error {
670 using std::runtime_error::runtime_error;
671 /// Set the error using the Python C API
672 virtual void set_error() const = 0;
675 #define PYBIND11_RUNTIME_EXCEPTION(name, type) \
676 class name : public builtin_exception { public: \
677 using builtin_exception::builtin_exception; \
678 name() : name("") { } \
679 void set_error() const override { PyErr_SetString(type, what()); } \
682 PYBIND11_RUNTIME_EXCEPTION(stop_iteration, PyExc_StopIteration)
683 PYBIND11_RUNTIME_EXCEPTION(index_error, PyExc_IndexError)
684 PYBIND11_RUNTIME_EXCEPTION(key_error, PyExc_KeyError)
685 PYBIND11_RUNTIME_EXCEPTION(value_error, PyExc_ValueError)
686 PYBIND11_RUNTIME_EXCEPTION(type_error, PyExc_TypeError)
687 PYBIND11_RUNTIME_EXCEPTION(buffer_error, PyExc_BufferError)
688 PYBIND11_RUNTIME_EXCEPTION(import_error, PyExc_ImportError)
689 PYBIND11_RUNTIME_EXCEPTION(cast_error, PyExc_RuntimeError) /// Thrown when pybind11::cast or handle::call fail due to a type casting error
690 PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used internally
692 [[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const char *reason) { throw std::runtime_error(reason); }
693 [[noreturn]] PYBIND11_NOINLINE inline void pybind11_fail(const std::string &reason) { throw std::runtime_error(reason); }
695 template <typename T, typename SFINAE = void> struct format_descriptor { };
697 NAMESPACE_BEGIN(detail)
698 // Returns the index of the given type in the type char array below, and in the list in numpy.h
699 // The order here is: bool; 8 ints ((signed,unsigned)x(8,16,32,64)bits); float,double,long double;
700 // complex float,double,long double. Note that the long double types only participate when long
701 // double is actually longer than double (it isn't under MSVC).
702 // NB: not only the string below but also complex.h and numpy.h rely on this order.
703 template <typename T, typename SFINAE = void> struct is_fmt_numeric { static constexpr bool value = false; };
704 template <typename T> struct is_fmt_numeric<T, enable_if_t<std::is_arithmetic<T>::value>> {
705 static constexpr bool value = true;
706 static constexpr int index = std::is_same<T, bool>::value ? 0 : 1 + (
707 std::is_integral<T>::value ? detail::log2(sizeof(T))*2 + std::is_unsigned<T>::value : 8 + (
708 std::is_same<T, double>::value ? 1 : std::is_same<T, long double>::value ? 2 : 0));
710 NAMESPACE_END(detail)
712 template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_arithmetic<T>::value>> {
713 static constexpr const char c = "?bBhHiIqQfdg"[detail::is_fmt_numeric<T>::index];
714 static constexpr const char value[2] = { c, '\0' };
715 static std::string format() { return std::string(1, c); }
718 #if !defined(PYBIND11_CPP17)
720 template <typename T> constexpr const char format_descriptor<
721 T, detail::enable_if_t<std::is_arithmetic<T>::value>>::value[2];
725 /// RAII wrapper that temporarily clears any Python error state
727 PyObject *type, *value, *trace;
728 error_scope() { PyErr_Fetch(&type, &value, &trace); }
729 ~error_scope() { PyErr_Restore(type, value, trace); }
732 /// Dummy destructor wrapper that can be used to expose classes with a private destructor
733 struct nodelete { template <typename T> void operator()(T*) { } };
735 NAMESPACE_BEGIN(detail)
736 template <typename... Args>
737 struct overload_cast_impl {
738 constexpr overload_cast_impl() {} // MSVC 2015 needs this
740 template <typename Return>
741 constexpr auto operator()(Return (*pf)(Args...)) const noexcept
742 -> decltype(pf) { return pf; }
744 template <typename Return, typename Class>
745 constexpr auto operator()(Return (Class::*pmf)(Args...), std::false_type = {}) const noexcept
746 -> decltype(pmf) { return pmf; }
748 template <typename Return, typename Class>
749 constexpr auto operator()(Return (Class::*pmf)(Args...) const, std::true_type) const noexcept
750 -> decltype(pmf) { return pmf; }
752 NAMESPACE_END(detail)
754 // overload_cast requires variable templates: C++14
755 #if defined(PYBIND11_CPP14)
756 #define PYBIND11_OVERLOAD_CAST 1
757 /// Syntax sugar for resolving overloaded function pointers:
758 /// - regular: static_cast<Return (Class::*)(Arg0, Arg1, Arg2)>(&Class::func)
759 /// - sweet: overload_cast<Arg0, Arg1, Arg2>(&Class::func)
760 template <typename... Args>
761 static constexpr detail::overload_cast_impl<Args...> overload_cast = {};
762 // MSVC 2015 only accepts this particular initialization syntax for this variable template.
765 /// Const member function selector for overload_cast
766 /// - regular: static_cast<Return (Class::*)(Arg) const>(&Class::func)
767 /// - sweet: overload_cast<Arg>(&Class::func, const_)
768 static constexpr auto const_ = std::true_type{};
770 #if !defined(PYBIND11_CPP14) // no overload_cast: providing something that static_assert-fails:
771 template <typename... Args> struct overload_cast {
772 static_assert(detail::deferred_t<std::false_type, Args...>::value,
773 "pybind11::overload_cast<...> requires compiling in C++14 mode");
775 #endif // overload_cast
777 NAMESPACE_BEGIN(detail)
779 // Adaptor for converting arbitrary container arguments into a vector; implicitly convertible from
780 // any standard container (or C-style array) supporting std::begin/std::end, any singleton
781 // arithmetic type (if T is arithmetic), or explicitly constructible from an iterator pair.
782 template <typename T>
783 class any_container {
786 any_container() = default;
788 // Can construct from a pair of iterators
789 template <typename It, typename = enable_if_t<is_input_iterator<It>::value>>
790 any_container(It first, It last) : v(first, last) { }
792 // Implicit conversion constructor from any arbitrary container type with values convertible to T
793 template <typename Container, typename = enable_if_t<std::is_convertible<decltype(*std::begin(std::declval<const Container &>())), T>::value>>
794 any_container(const Container &c) : any_container(std::begin(c), std::end(c)) { }
796 // initializer_list's aren't deducible, so don't get matched by the above template; we need this
797 // to explicitly allow implicit conversion from one:
798 template <typename TIn, typename = enable_if_t<std::is_convertible<TIn, T>::value>>
799 any_container(const std::initializer_list<TIn> &c) : any_container(c.begin(), c.end()) { }
801 // Avoid copying if given an rvalue vector of the correct type.
802 any_container(std::vector<T> &&v) : v(std::move(v)) { }
804 // Moves the vector out of an rvalue any_container
805 operator std::vector<T> &&() && { return std::move(v); }
807 // Dereferencing obtains a reference to the underlying vector
808 std::vector<T> &operator*() { return v; }
809 const std::vector<T> &operator*() const { return v; }
811 // -> lets you call methods on the underlying vector
812 std::vector<T> *operator->() { return &v; }
813 const std::vector<T> *operator->() const { return &v; }
816 NAMESPACE_END(detail)
820 NAMESPACE_END(PYBIND11_NAMESPACE)