Merge pull request #410 from wjakob/mi

WIP: Multiple inheritance support

README.md

@@ -45,10 +45,12 @@ pybind11 can map the following core C++ features to Python
 - Arbitrary exception types
 - Enumerations
 - Callbacks
+- Iterators and ranges
 - Custom operators
+- Single and multiple inheritance
 - STL data structures
 - Iterators and ranges
-- Smart pointers with reference counting like `std::shared_ptr`
+- Smart pointers with reference counting like ``std::shared_ptr``
 - Internal references with correct reference counting
 - C++ classes with virtual (and pure virtual) methods can be extended in Python
 

docs/advanced.rst

@@ -217,6 +217,8 @@ The following interactive session shows how to call them from Python.
     that demonstrates how to work with callbacks and anonymous functions in
     more detail.
 
+.. _overriding_virtuals:
+
 Overriding virtual functions in Python
 ======================================
 
@@ -2151,3 +2153,45 @@ type is explicitly allowed.
             };
         }
     };
+
+Multiple Inheritance
+====================
+
+pybind11 can create bindings for types that derive from multiple base types
+(aka. *multiple inheritance*). To do so, specify all bases in the template
+arguments of the ``class_`` declaration:
+
+.. code-block:: cpp
+
+    py::class_<MyType, BaseType1, BaseType2, BaseType3>(m, "MyType")
+       ...
+
+The base types can be specified in arbitrary order, and they can even be
+interspersed with alias types and holder types (discussed earlier in this
+document)---pybind11 will automatically find out which is which. The only
+requirement is that the first template argument is the type to be declared.
+
+There are two caveats regarding the implementation of this feature:
+
+1. When only one base type is specified for a C++ type that actually has
+   multiple bases, pybind11 will assume that it does not participate in
+   multiple inheritance, which can lead to undefined behavior. In such cases,
+   add the tag ``multiple_inheritance``:
+
+    .. code-block:: cpp
+
+        py::class_<MyType, BaseType2>(m, "MyType", py::multiple_inheritance());
+
+   The tag is redundant and does not need to be specified when multiple base
+   types are listed.
+
+2. As was previously discussed in the section on :ref:`overriding_virtuals`, it
+   is easy to create Python types that derive from C++ classes. It is even
+   possible to make use of multiple inheritance to declare a Python class which
+   has e.g. a C++ and a Python class as bases. However, any attempt to create a
+   type that has *two or more* C++ classes in its hierarchy of base types will
+   fail with a fatal error message: ``TypeError: multiple bases have instance
+   lay-out conflict``. Core Python types that are implemented in C (e.g.
+   ``dict``, ``list``, ``Exception``, etc.) also fall under this combination
+   and cannot be combined with C++ types bound using pybind11 via multiple
+   inheritance.

docs/classes.rst

@@ -185,10 +185,9 @@ inheritance relationship:
         std::string bark() const { return "woof!"; }
     };
 
-There are three different ways of indicating a hierarchical relationship to
+There are two different ways of indicating a hierarchical relationship to
 pybind11: the first specifies the C++ base class as an extra template
-parameter of the :class:`class_`; the second uses a special ``base`` attribute
-passed into the constructor:
+parameter of the :class:`class_`:
 
 .. code-block:: cpp
 
@@ -201,11 +200,6 @@ passed into the constructor:
         .def(py::init<const std::string &>())
         .def("bark", &Dog::bark);
 
-    // Method 2: py::base attribute:
-    py::class_<Dog>(m, "Dog", py::base<Pet>() /* <- specify C++ parent type */)
-        .def(py::init<const std::string &>())
-        .def("bark", &Dog::bark);
-
 Alternatively, we can also assign a name to the previously bound ``Pet``
 :class:`class_` object and reference it when binding the ``Dog`` class:
 
@@ -215,13 +209,13 @@ Alternatively, we can also assign a name to the previously bound ``Pet``
     pet.def(py::init<const std::string &>())
        .def_readwrite("name", &Pet::name);
 
-    // Method 3: pass parent class_ object:
+    // Method 2: pass parent class_ object:
     py::class_<Dog>(m, "Dog", pet /* <- specify Python parent type */)
         .def(py::init<const std::string &>())
         .def("bark", &Dog::bark);
 
-Functionality-wise, all three approaches are completely equivalent. Afterwards,
-instances will expose fields and methods of both types:
+Functionality-wise, both approaches are equivalent. Afterwards, instances will
+expose fields and methods of both types:
 
 .. code-block:: pycon
 

docs/intro.rst

@@ -35,12 +35,14 @@ The following core C++ features can be mapped to Python
 - Instance methods and static methods
 - Overloaded functions
 - Instance attributes and static attributes
-- Exceptions
+- Arbitrary exception types
 - Enumerations
-- Iterators and ranges
 - Callbacks
+- Iterators and ranges
 - Custom operators
+- Single and multiple inheritance
 - STL data structures
+- Iterators and ranges
 - Smart pointers with reference counting like ``std::shared_ptr``
 - Internal references with correct reference counting
 - C++ classes with virtual (and pure virtual) methods can be extended in Python

docs/limitations.rst

@@ -9,15 +9,12 @@ certain limitations:
   values. This means that some additional care is needed to avoid bugs that
   would be caught by the type checker in a traditional C++ program.
 
-- Multiple inheritance relationships on the C++ side cannot be mapped to
-  Python.
-
 - The NumPy interface ``pybind11::array`` greatly simplifies accessing
   numerical data from C++ (and vice versa), but it's not a full-blown array
   class like ``Eigen::Array`` or ``boost.multi_array``.
 
-All of these features could be implemented but would lead to a significant
-increase in complexity. I've decided to draw the line here to keep this project
-simple and compact. Users who absolutely require these features are encouraged
-to fork pybind11.
+These features could be implemented but would lead to a significant increase in
+complexity. I've decided to draw the line here to keep this project simple and
+compact. Users who absolutely require these features are encouraged to fork
+pybind11.
 

include/pybind11/attr.h

@@ -33,11 +33,17 @@ struct name { const char *value; name(const char *value) : value(value) { } };
 struct sibling { handle value; sibling(const handle &value) : value(value.ptr()) { } };
 
 /// Annotation indicating that a class derives from another given type
-template <typename T> struct base { };
+template <typename T> struct base {
+    PYBIND11_DEPRECATED("base<T>() was deprecated in favor of specifying 'T' as a template argument to class_")
+    base() { }
+};
 
 /// Keep patient alive while nurse lives
 template <int Nurse, int Patient> struct keep_alive { };
 
+/// Annotation indicating that a class is involved in a multiple inheritance relationship
+struct multiple_inheritance { };
+
 NAMESPACE_BEGIN(detail)
 /* Forward declarations */
 enum op_id : int;
@@ -124,6 +130,8 @@ struct function_record {
 
 /// Special data structure which (temporarily) holds metadata about a bound class
 struct type_record {
+    PYBIND11_NOINLINE type_record() { }
+
     /// Handle to the parent scope
     handle scope;
 
@@ -145,21 +153,36 @@ struct type_record {
     /// Function pointer to class_<..>::dealloc
     void (*dealloc)(PyObject *) = nullptr;
 
-    // Pointer to RTTI type_info data structure of base class
-    const std::type_info *base_type = nullptr;
-
-    /// OR: Python handle to base class
-    handle base_handle;
+    /// List of base classes of the newly created type
+    list bases;
 
     /// Optional docstring
     const char *doc = nullptr;
+
+    /// Multiple inheritance marker
+    bool multiple_inheritance = false;
+
+    PYBIND11_NOINLINE void add_base(const std::type_info *base, void *(*caster)(void *)) {
+        auto base_info = detail::get_type_info(*base, false);
+        if (!base_info) {
+            std::string tname(base->name());
+            detail::clean_type_id(tname);
+            pybind11_fail("generic_type: type \"" + std::string(name) +
+                          "\" referenced unknown base type \"" + tname + "\"");
+        }
+
+        bases.append((PyObject *) base_info->type);
+
+        if (caster)
+            base_info->implicit_casts.push_back(std::make_pair(type, caster));
+    }
 };
 
 /**
  * Partial template specializations to process custom attributes provided to
  * cpp_function_ and class_. These are either used to initialize the respective
- * fields in the type_record and function_record data structures or executed
- * at runtime to deal with custom call policies (e.g. keep_alive).
+ * fields in the type_record and function_record data structures or executed at
+ * runtime to deal with custom call policies (e.g. keep_alive).
  */
 template <typename T, typename SFINAE = void> struct process_attribute;
 
@@ -253,14 +276,20 @@ template <> struct process_attribute<arg_v> : process_attribute_default<arg_v> {
 
 /// Process a parent class attribute
 template <typename T>
-struct process_attribute<T, typename std::enable_if<std::is_base_of<handle, T>::value>::type> : process_attribute_default<handle> {
-    static void init(const handle &h, type_record *r) { r->base_handle = h; }
+struct process_attribute<T, enable_if_t<std::is_base_of<handle, T>::value>> : process_attribute_default<handle> {
+    static void init(const handle &h, type_record *r) { r->bases.append(h); }
 };
 
-/// Process a parent class attribute
+/// Process a parent class attribute (deprecated, does not support multiple inheritance)
 template <typename T>
 struct process_attribute<base<T>> : process_attribute_default<base<T>> {
-    static void init(const base<T> &, type_record *r) { r->base_type = &typeid(T); }
+    static void init(const base<T> &, type_record *r) { r->add_base(&typeid(T), nullptr); }
+};
+
+/// Process a multiple inheritance attribute
+template <>
+struct process_attribute<multiple_inheritance> : process_attribute_default<multiple_inheritance> {
+    static void init(const multiple_inheritance &, type_record *r) { r->multiple_inheritance = true; }
 };
 
 /***
@@ -269,13 +298,13 @@ struct process_attribute<base<T>> : process_attribute_default<base<T>> {
  * otherwise
  */
 template <int Nurse, int Patient> struct process_attribute<keep_alive<Nurse, Patient>> : public process_attribute_default<keep_alive<Nurse, Patient>> {
-    template <int N = Nurse, int P = Patient, typename std::enable_if<N != 0 && P != 0, int>::type = 0>
+    template <int N = Nurse, int P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
     static void precall(handle args) { keep_alive_impl(Nurse, Patient, args, handle()); }
-    template <int N = Nurse, int P = Patient, typename std::enable_if<N != 0 && P != 0, int>::type = 0>
+    template <int N = Nurse, int P = Patient, enable_if_t<N != 0 && P != 0, int> = 0>
     static void postcall(handle, handle) { }
-    template <int N = Nurse, int P = Patient, typename std::enable_if<N == 0 || P == 0, int>::type = 0>
+    template <int N = Nurse, int P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
     static void precall(handle) { }
-    template <int N = Nurse, int P = Patient, typename std::enable_if<N == 0 || P == 0, int>::type = 0>
+    template <int N = Nurse, int P = Patient, enable_if_t<N == 0 || P == 0, int> = 0>
     static void postcall(handle args, handle ret) { keep_alive_impl(Nurse, Patient, args, ret); }
 };
 

include/pybind11/cast.h

@@ -15,7 +15,6 @@
 #include "descr.h"
 #include <array>
 #include <limits>
-#include <iostream>
 
 NAMESPACE_BEGIN(pybind11)
 NAMESPACE_BEGIN(detail)
@@ -25,9 +24,13 @@ struct type_info {
     PyTypeObject *type;
     size_t type_size;
     void (*init_holder)(PyObject *, const void *);
-    std::vector<PyObject *(*)(PyObject *, PyTypeObject *) > implicit_conversions;
+    std::vector<PyObject *(*)(PyObject *, PyTypeObject *)> implicit_conversions;
+    std::vector<std::pair<const std::type_info *, void *(*)(void *)>> implicit_casts;
     buffer_info *(*get_buffer)(PyObject *, void *) = nullptr;
     void *get_buffer_data = nullptr;
+    /** A simple type never occurs as a (direct or indirect) parent
+     * of a class that makes use of multiple inheritance */
+    bool simple_type = true;
 };
 
 PYBIND11_NOINLINE inline internals &get_internals() {
@@ -72,32 +75,34 @@ PYBIND11_NOINLINE inline internals &get_internals() {
     return *internals_ptr;
 }
 
-PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type, bool throw_if_missing = true) {
+PYBIND11_NOINLINE inline detail::type_info* get_type_info(PyTypeObject *type) {
     auto const &type_dict = get_internals().registered_types_py;
     do {
         auto it = type_dict.find(type);
         if (it != type_dict.end())
             return (detail::type_info *) it->second;
         type = type->tp_base;
-        if (!type) {
-            if (throw_if_missing)
-                pybind11_fail("pybind11::detail::get_type_info: unable to find type object!");
+        if (!type)
             return nullptr;
-        }
     } while (true);
 }
 
-PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_info &tp) {
+PYBIND11_NOINLINE inline detail::type_info *get_type_info(const std::type_info &tp, bool throw_if_missing) {
     auto &types = get_internals().registered_types_cpp;
 
     auto it = types.find(std::type_index(tp));
     if (it != types.end())
         return (detail::type_info *) it->second;
+    if (throw_if_missing) {
+        std::string tname = tp.name();
+        detail::clean_type_id(tname);
+        pybind11_fail("pybind11::detail::get_type_info: unable to find type info for \"" + tname + "\"");
+    }
     return nullptr;
 }
 
-PYBIND11_NOINLINE inline handle get_type_handle(const std::type_info &tp) {
-    detail::type_info *type_info = get_type_info(tp);
+PYBIND11_NOINLINE inline handle get_type_handle(const std::type_info &tp, bool throw_if_missing) {
+    detail::type_info *type_info = get_type_info(tp, throw_if_missing);
     return handle(type_info ? ((PyObject *) type_info->type) : nullptr);
 }
 
@@ -124,7 +129,7 @@ PYBIND11_NOINLINE inline handle get_object_handle(const void *ptr, const detail:
     auto &instances = get_internals().registered_instances;
     auto range = instances.equal_range(ptr);
     for (auto it = range.first; it != range.second; ++it) {
-        auto instance_type = detail::get_type_info(Py_TYPE(it->second), false);
+        auto instance_type = detail::get_type_info(Py_TYPE(it->second));
         if (instance_type && instance_type == type)
             return handle((PyObject *) it->second);
     }
@@ -149,18 +154,56 @@ inline void keep_alive_impl(handle nurse, handle patient);
 class type_caster_generic {
 public:
     PYBIND11_NOINLINE type_caster_generic(const std::type_info &type_info)
-     : typeinfo(get_type_info(type_info)) { }
+     : typeinfo(get_type_info(type_info, false)) { }
 
     PYBIND11_NOINLINE bool load(handle src, bool convert) {
+        return load(src, convert, Py_TYPE(src.ptr()));
+    }
+
+    bool load(handle src, bool convert, PyTypeObject *tobj) {
         if (!src || !typeinfo)
             return false;
         if (src.is_none()) {
             value = nullptr;
             return true;
-        } else if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
-            value = ((instance<void> *) src.ptr())->value;
-            return true;
         }
+
+        if (typeinfo->simple_type) { /* Case 1: no multiple inheritance etc. involved */
+            /* Check if we can safely perform a reinterpret-style cast */
+            if (PyType_IsSubtype(tobj, typeinfo->type)) {
+                value = reinterpret_cast<instance<void> *>(src.ptr())->value;
+                return true;
+            }
+        } else { /* Case 2: multiple inheritance */
+            /* Check if we can safely perform a reinterpret-style cast */
+            if (tobj == typeinfo->type) {
+                value = reinterpret_cast<instance<void> *>(src.ptr())->value;
+                return true;
+            }
+
+            /* If this is a python class, also check the parents recursively */
+            auto const &type_dict = get_internals().registered_types_py;
+            bool new_style_class = PyType_Check(tobj);
+            if (type_dict.find(tobj) == type_dict.end() && new_style_class && tobj->tp_bases) {
+                tuple parents(tobj->tp_bases, true);
+                for (handle parent : parents) {
+                    bool result = load(src, convert, (PyTypeObject *) parent.ptr());
+                    if (result)
+                        return true;
+                }
+            }
+
+            /* Try implicit casts */
+            for (auto &cast : typeinfo->implicit_casts) {
+                type_caster_generic sub_caster(*cast.first);
+                if (sub_caster.load(src, convert)) {
+                    value = cast.second(sub_caster.value);
+                    return true;
+                }
+            }
+        }
+
+        /* Perform an implicit conversion */
         if (convert) {
             for (auto &converter : typeinfo->implicit_conversions) {
                 temp = object(converter(src.ptr(), typeinfo->type), false);
@@ -201,7 +244,7 @@ public:
 
         auto it_instances = internals.registered_instances.equal_range(src);
         for (auto it_i = it_instances.first; it_i != it_instances.second; ++it_i) {
-            auto instance_type = detail::get_type_info(Py_TYPE(it_i->second), false);
+            auto instance_type = detail::get_type_info(Py_TYPE(it_i->second));
             if (instance_type && instance_type == tinfo)
                 return handle((PyObject *) it_i->second).inc_ref();
         }
@@ -262,7 +305,8 @@ template <typename type> class type_caster_base : public type_caster_generic {
 public:
     static PYBIND11_DESCR name() { return type_descr(_<type>()); }
 
-    type_caster_base() : type_caster_generic(typeid(type)) { }
+    type_caster_base() : type_caster_base(typeid(type)) { }
+    type_caster_base(const std::type_info &info) : type_caster_generic(info) { }
 
     static handle cast(const itype &src, return_value_policy policy, handle parent) {
         if (policy == return_value_policy::automatic || policy == return_value_policy::automatic_reference)
@@ -299,10 +343,10 @@ protected:
 #else
     /* Visual Studio 2015's SFINAE implementation doesn't yet handle the above robustly in all situations.
        Use a workaround that only tests for constructibility for now. */
-    template <typename T = type, typename = typename std::enable_if<std::is_copy_constructible<T>::value>::type>
+    template <typename T = type, typename = enable_if_t<std::is_copy_constructible<T>::value>>
     static Constructor make_copy_constructor(const T *value) {
         return [](const void *arg) -> void * { return new T(*((const T *)arg)); }; }
-    template <typename T = type, typename = typename std::enable_if<std::is_move_constructible<T>::value>::type>
+    template <typename T = type, typename = enable_if_t<std::is_move_constructible<T>::value>>
     static Constructor make_move_constructor(const T *value) {
         return [](const void *arg) -> void * { return (void *) new T(std::move(*((T *)arg))); }; }
 #endif
@@ -343,8 +387,8 @@ public:
 
 template <typename T>
 struct type_caster<
-    T, typename std::enable_if<std::is_integral<T>::value ||
-                               std::is_floating_point<T>::value>::type> {
+    T, enable_if_t<std::is_integral<T>::value ||
+                   std::is_floating_point<T>::value>> {
     typedef typename std::conditional<sizeof(T) <= sizeof(long), long, long long>::type _py_type_0;
     typedef typename std::conditional<std::is_signed<T>::value, _py_type_0, typename std::make_unsigned<_py_type_0>::type>::type _py_type_1;
     typedef typename std::conditional<std::is_floating_point<T>::value, double, _py_type_1>::type py_type;
@@ -433,7 +477,7 @@ public:
         }
 
         /* Check if this is a C++ type */
-        if (get_type_info((PyTypeObject *) h.get_type().ptr(), false)) {
+        if (get_type_info((PyTypeObject *) h.get_type().ptr())) {
             value = ((instance<void> *) h.ptr())->value;
             return true;
         }
@@ -658,20 +702,20 @@ public:
         return load(src, convert, typename make_index_sequence<sizeof...(Tuple)>::type());
     }
 
-    template <typename T = itype, typename std::enable_if<
+    template <typename T = itype, enable_if_t<
         !std::is_same<T, args_type>::value &&
-        !std::is_same<T, args_kwargs_type>::value, int>::type = 0>
+        !std::is_same<T, args_kwargs_type>::value, int> = 0>
     bool load_args(handle args, handle, bool convert) {
         return load(args, convert, typename make_index_sequence<sizeof...(Tuple)>::type());
     }
 
-    template <typename T = itype, typename std::enable_if<std::is_same<T, args_type>::value, int>::type = 0>
+    template <typename T = itype, enable_if_t<std::is_same<T, args_type>::value, int> = 0>
     bool load_args(handle args, handle, bool convert) {
         std::get<0>(value).load(args, convert);
         return true;
     }
 
-    template <typename T = itype, typename std::enable_if<std::is_same<T, args_kwargs_type>::value, int>::type = 0>
+    template <typename T = itype, enable_if_t<std::is_same<T, args_kwargs_type>::value, int> = 0>
     bool load_args(handle args, handle kwargs, bool convert) {
         std::get<0>(value).load(args, convert);
         std::get<1>(value).load(kwargs, convert);
@@ -690,11 +734,11 @@ public:
         return type_descr(_("Tuple[") + element_names() + _("]"));
     }
 
-    template <typename ReturnValue, typename Func> typename std::enable_if<!std::is_void<ReturnValue>::value, ReturnValue>::type call(Func &&f) {
+    template <typename ReturnValue, typename Func> enable_if_t<!std::is_void<ReturnValue>::value, ReturnValue> call(Func &&f) {
         return call<ReturnValue>(std::forward<Func>(f), typename make_index_sequence<sizeof...(Tuple)>::type());
     }
 
-    template <typename ReturnValue, typename Func> typename std::enable_if<std::is_void<ReturnValue>::value, void_type>::type call(Func &&f) {
+    template <typename ReturnValue, typename Func> enable_if_t<std::is_void<ReturnValue>::value, void_type> call(Func &&f) {
         call<ReturnValue>(std::forward<Func>(f), typename make_index_sequence<sizeof...(Tuple)>::type());
         return void_type();
     }
@@ -749,22 +793,56 @@ protected:
 /// Type caster for holder types like std::shared_ptr, etc.
 template <typename type, typename holder_type> class type_caster_holder : public type_caster_base<type> {
 public:
-    using type_caster_base<type>::cast;
-    using type_caster_base<type>::typeinfo;
-    using type_caster_base<type>::value;
-    using type_caster_base<type>::temp;
+    using base = type_caster_base<type>;
+    using base::base;
+    using base::cast;
+    using base::typeinfo;
+    using base::value;
+    using base::temp;
 
-    bool load(handle src, bool convert) {
-        if (!src || !typeinfo) {
+    PYBIND11_NOINLINE bool load(handle src, bool convert) {
+        return load(src, convert, Py_TYPE(src.ptr()));
+    }
+
+    bool load(handle src, bool convert, PyTypeObject *tobj) {
+        if (!src || !typeinfo)
             return false;
-        } else if (src.is_none()) {
+        if (src.is_none()) {
             value = nullptr;
             return true;
-        } else if (PyType_IsSubtype(Py_TYPE(src.ptr()), typeinfo->type)) {
-            auto inst = (instance<type, holder_type> *) src.ptr();
-            value = (void *) inst->value;
-            holder = inst->holder;
-            return true;
+        }
+
+        if (typeinfo->simple_type) { /* Case 1: no multiple inheritance etc. involved */
+            /* Check if we can safely perform a reinterpret-style cast */
+            if (PyType_IsSubtype(tobj, typeinfo->type)) {
+                auto inst = (instance<type, holder_type> *) src.ptr();
+                value = (void *) inst->value;
+                holder = inst->holder;
+                return true;
+            }
+        } else { /* Case 2: multiple inheritance */
+            /* Check if we can safely perform a reinterpret-style cast */
+            if (tobj == typeinfo->type) {
+                auto inst = (instance<type, holder_type> *) src.ptr();
+                value = (void *) inst->value;
+                holder = inst->holder;
+                return true;
+            }
+
+            /* If this is a python class, also check the parents recursively */
+            auto const &type_dict = get_internals().registered_types_py;
+            bool new_style_class = PyType_Check(tobj);
+            if (type_dict.find(tobj) == type_dict.end() && new_style_class && tobj->tp_bases) {
+                tuple parents(tobj->tp_bases, true);
+                for (handle parent : parents) {
+                    bool result = load(src, convert, (PyTypeObject *) parent.ptr());
+                    if (result)
+                        return true;
+                }
+            }
+
+            if (try_implicit_casts(src, convert))
+                return true;
         }
 
         if (convert) {
@@ -774,6 +852,23 @@ public:
                     return true;
             }
         }
+
+        return false;
+    }
+
+    template <typename T = holder_type, detail::enable_if_t<!std::is_constructible<T, const T &, type*>::value, int> = 0>
+    bool try_implicit_casts(handle, bool) { return false; }
+
+    template <typename T = holder_type, detail::enable_if_t<std::is_constructible<T, const T &, type*>::value, int> = 0>
+    bool try_implicit_casts(handle src, bool convert) {
+        for (auto &cast : typeinfo->implicit_casts) {
+            type_caster_holder sub_caster(*cast.first);
+            if (sub_caster.load(src, convert)) {
+                value = cast.second(sub_caster.value);
+                holder = holder_type(sub_caster.holder, (type *) value);
+                return true;
+            }
+        }
         return false;
     }
 
@@ -813,12 +908,12 @@ template <> struct handle_type_name<args> { static PYBIND11_DESCR name() { retur
 template <> struct handle_type_name<kwargs> { static PYBIND11_DESCR name() { return _("**kwargs"); } };
 
 template <typename type>
-struct type_caster<type, typename std::enable_if<std::is_base_of<handle, type>::value>::type> {
+struct type_caster<type, enable_if_t<std::is_base_of<handle, type>::value>> {
 public:
-    template <typename T = type, typename std::enable_if<!std::is_base_of<object, T>::value, int>::type = 0>
+    template <typename T = type, enable_if_t<!std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) { value = type(src); return value.check(); }
 
-    template <typename T = type, typename std::enable_if<std::is_base_of<object, T>::value, int>::type = 0>
+    template <typename T = type, enable_if_t<std::is_base_of<object, T>::value, int> = 0>
     bool load(handle src, bool /* convert */) { value = type(src, true); return value.check(); }
 
     static handle cast(const handle &src, return_value_policy /* policy */, handle /* parent */) {
@@ -837,21 +932,21 @@ public:
 //   must have ref_count() == 1)h
 // If any of the above are not satisfied, we fall back to copying.
 template <typename T, typename SFINAE = void> struct move_is_plain_type : std::false_type {};
-template <typename T> struct move_is_plain_type<T, typename std::enable_if<
+template <typename T> struct move_is_plain_type<T, enable_if_t<
         !std::is_void<T>::value && !std::is_pointer<T>::value && !std::is_reference<T>::value && !std::is_const<T>::value
-    >::type> : std::true_type {};
+    >> : std::true_type { };
 template <typename T, typename SFINAE = void> struct move_always : std::false_type {};
-template <typename T> struct move_always<T, typename std::enable_if<
+template <typename T> struct move_always<T, enable_if_t<
         move_is_plain_type<T>::value &&
         !std::is_copy_constructible<T>::value && std::is_move_constructible<T>::value &&
         std::is_same<decltype(std::declval<type_caster<T>>().operator T&()), T&>::value
-    >::type> : std::true_type {};
+    >> : std::true_type { };
 template <typename T, typename SFINAE = void> struct move_if_unreferenced : std::false_type {};
-template <typename T> struct move_if_unreferenced<T, typename std::enable_if<
+template <typename T> struct move_if_unreferenced<T, enable_if_t<
         move_is_plain_type<T>::value &&
         !move_always<T>::value && std::is_move_constructible<T>::value &&
         std::is_same<decltype(std::declval<type_caster<T>>().operator T&()), T&>::value
-    >::type> : std::true_type {};
+    >> : std::true_type { };
 template <typename T> using move_never = std::integral_constant<bool, !move_always<T>::value && !move_if_unreferenced<T>::value>;
 
 // Detect whether returning a `type` from a cast on type's type_caster is going to result in a
@@ -968,7 +1063,6 @@ template <> inline void cast_safe<void>(object &&) {}
 
 NAMESPACE_END(detail)
 
-
 template <return_value_policy policy = return_value_policy::automatic_reference,
           typename... Args> tuple make_tuple(Args&&... args_) {
     const size_t size = sizeof...(Args);
@@ -1023,7 +1117,7 @@ struct arg_v : arg {
 template <typename T>
 arg_v arg::operator=(T &&value) const { return {name, std::forward<T>(value)}; }
 
-/// Alias for backward compatibility -- to be remove in version 2.0
+/// Alias for backward compatibility -- to be removed in version 2.0
 template <typename /*unused*/> using arg_t = arg_v;
 
 inline namespace literals {
@@ -1199,7 +1293,7 @@ unpacking_collector<policy> collect_arguments(Args &&...args) {
         "Invalid function call: positional args must precede keywords and ** unpacking; "
         "* unpacking must precede ** unpacking"
     );
-    return {std::forward<Args>(args)...};
+    return { std::forward<Args>(args)... };
 }
 
 NAMESPACE_END(detail)

include/pybind11/common.h

@@ -30,6 +30,16 @@
 #  define PYBIND11_NOINLINE __attribute__ ((noinline))
 #endif
 
+#if __cplusplus > 201103L
+#  define PYBIND11_DEPRECATED(reason) [[deprecated(reason)]]
+#elif defined(__clang__)
+#  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated(reason)))
+#elif defined(__GNUG__)
+#  define PYBIND11_DEPRECATED(reason) __attribute__((deprecated))
+#elif defined(_MSC_VER)
+#  define PYBIND11_DEPRECATED(reason) __declspec(deprecated)
+#endif
+
 #define PYBIND11_VERSION_MAJOR 1
 #define PYBIND11_VERSION_MINOR 9
 #define PYBIND11_VERSION_PATCH dev0
@@ -79,6 +89,7 @@
 #include <unordered_map>
 #include <memory>
 #include <typeindex>
+#include <type_traits>
 
 #if PY_MAJOR_VERSION >= 3 /// Compatibility macros for various Python versions
 #define PYBIND11_INSTANCE_METHOD_NEW(ptr, class_) PyInstanceMethod_New(ptr)
@@ -431,14 +442,14 @@ PYBIND11_RUNTIME_EXCEPTION(reference_cast_error, PyExc_RuntimeError) /// Used in
 
 template <typename T, typename SFINAE = void> struct format_descriptor { };
 
-template <typename T> struct format_descriptor<T, typename std::enable_if<std::is_integral<T>::value>::type> {
+template <typename T> struct format_descriptor<T, detail::enable_if_t<std::is_integral<T>::value>> {
     static constexpr const char value[2] =
         { "bBhHiIqQ"[detail::log2(sizeof(T))*2 + (std::is_unsigned<T>::value ? 1 : 0)], '\0' };
     static std::string format() { return value; }
 };
 
 template <typename T> constexpr const char format_descriptor<
-    T, typename std::enable_if<std::is_integral<T>::value>::type>::value[2];
+    T, detail::enable_if_t<std::is_integral<T>::value>>::value[2];
 
 /// RAII wrapper that temporarily clears any Python error state
 struct error_scope {

include/pybind11/descr.h

@@ -86,11 +86,11 @@ template <size_t...Digits> struct int_to_str<0, Digits...> {
 
 // Ternary description (like std::conditional)
 template <bool B, size_t Size1, size_t Size2>
-constexpr typename std::enable_if<B, descr<Size1 - 1, 0>>::type _(char const(&text1)[Size1], char const(&)[Size2]) {
+constexpr enable_if_t<B, descr<Size1 - 1, 0>> _(char const(&text1)[Size1], char const(&)[Size2]) {
     return _(text1);
 }
 template <bool B, size_t Size1, size_t Size2>
-constexpr typename std::enable_if<!B, descr<Size2 - 1, 0>>::type _(char const(&)[Size1], char const(&text2)[Size2]) {
+constexpr enable_if_t<!B, descr<Size2 - 1, 0>> _(char const(&)[Size1], char const(&text2)[Size2]) {
     return _(text2);
 }
 
@@ -164,8 +164,8 @@ PYBIND11_NOINLINE inline descr _(const char *text) {
     return descr(text, types);
 }
 
-template <bool B> PYBIND11_NOINLINE typename std::enable_if<B, descr>::type _(const char *text1, const char *) { return _(text1); }
-template <bool B> PYBIND11_NOINLINE typename std::enable_if<!B, descr>::type _(char const *, const char *text2) { return _(text2); }
+template <bool B> PYBIND11_NOINLINE enable_if_t<B, descr> _(const char *text1, const char *) { return _(text1); }
+template <bool B> PYBIND11_NOINLINE enable_if_t<!B, descr> _(char const *, const char *text2) { return _(text2); }
 
 template <typename Type> PYBIND11_NOINLINE descr _() {
     const std::type_info *types[2] = { &typeid(Type), nullptr };

include/pybind11/eigen.h

@@ -46,9 +46,9 @@ public:
 // type_caster to handle argument copying/forwarding.
 template <typename T> class is_eigen_ref {
 private:
-    template<typename Derived> static typename std::enable_if<
+    template<typename Derived> static enable_if_t<
         std::is_same<typename std::remove_const<T>::type, Eigen::Ref<Derived>>::value,
-        Derived>::type test(const Eigen::Ref<Derived> &);
+        Derived> test(const Eigen::Ref<Derived> &);
     static void test(...);
 public:
     typedef decltype(test(std::declval<T>())) Derived;
@@ -77,7 +77,7 @@ public:
 };
 
 template<typename Type>
-struct type_caster<Type, typename std::enable_if<is_eigen_dense<Type>::value && !is_eigen_ref<Type>::value>::type> {
+struct type_caster<Type, enable_if_t<is_eigen_dense<Type>::value && !is_eigen_ref<Type>::value>> {
     typedef typename Type::Scalar Scalar;
     static constexpr bool rowMajor = Type::Flags & Eigen::RowMajorBit;
     static constexpr bool isVector = Type::IsVectorAtCompileTime;
@@ -149,18 +149,18 @@ struct type_caster<Type, typename std::enable_if<is_eigen_dense<Type>::value &&
             _("[") + rows() + _(", ") + cols() + _("]]"));
 
 protected:
-    template <typename T = Type, typename std::enable_if<T::RowsAtCompileTime == Eigen::Dynamic, int>::type = 0>
+    template <typename T = Type, enable_if_t<T::RowsAtCompileTime == Eigen::Dynamic, int> = 0>
     static PYBIND11_DESCR rows() { return _("m"); }
-    template <typename T = Type, typename std::enable_if<T::RowsAtCompileTime != Eigen::Dynamic, int>::type = 0>
+    template <typename T = Type, enable_if_t<T::RowsAtCompileTime != Eigen::Dynamic, int> = 0>
     static PYBIND11_DESCR rows() { return _<T::RowsAtCompileTime>(); }
-    template <typename T = Type, typename std::enable_if<T::ColsAtCompileTime == Eigen::Dynamic, int>::type = 0>
+    template <typename T = Type, enable_if_t<T::ColsAtCompileTime == Eigen::Dynamic, int> = 0>
     static PYBIND11_DESCR cols() { return _("n"); }
-    template <typename T = Type, typename std::enable_if<T::ColsAtCompileTime != Eigen::Dynamic, int>::type = 0>
+    template <typename T = Type, enable_if_t<T::ColsAtCompileTime != Eigen::Dynamic, int> = 0>
     static PYBIND11_DESCR cols() { return _<T::ColsAtCompileTime>(); }
 };
 
 template<typename Type>
-struct type_caster<Type, typename std::enable_if<is_eigen_dense<Type>::value && is_eigen_ref<Type>::value>::type> {
+struct type_caster<Type, enable_if_t<is_eigen_dense<Type>::value && is_eigen_ref<Type>::value>> {
 protected:
     using Derived = typename std::remove_const<typename is_eigen_ref<Type>::Derived>::type;
     using DerivedCaster = type_caster<Derived>;
@@ -181,7 +181,7 @@ public:
 // type_caster for special matrix types (e.g. DiagonalMatrix): load() is not supported, but we can
 // cast them into the python domain by first copying to a regular Eigen::Matrix, then casting that.
 template <typename Type>
-struct type_caster<Type, typename std::enable_if<is_eigen_base<Type>::value && !is_eigen_ref<Type>::value>::type> {
+struct type_caster<Type, enable_if_t<is_eigen_base<Type>::value && !is_eigen_ref<Type>::value>> {
 protected:
     using Matrix = Eigen::Matrix<typename Type::Scalar, Eigen::Dynamic, Eigen::Dynamic>;
     using MatrixCaster = type_caster<Matrix>;
@@ -198,7 +198,7 @@ public:
 };
 
 template<typename Type>
-struct type_caster<Type, typename std::enable_if<is_eigen_sparse<Type>::value>::type> {
+struct type_caster<Type, enable_if_t<is_eigen_sparse<Type>::value>> {
     typedef typename Type::Scalar Scalar;
     typedef typename std::remove_reference<decltype(*std::declval<Type>().outerIndexPtr())>::type StorageIndex;
     typedef typename Type::Index Index;

include/pybind11/numpy.h

@@ -486,7 +486,7 @@ public:
 };
 
 template <typename T>
-struct format_descriptor<T, typename std::enable_if<detail::is_pod_struct<T>::value>::type> {
+struct format_descriptor<T, detail::enable_if_t<detail::is_pod_struct<T>::value>> {
     static std::string format() {
         return detail::npy_format_descriptor<typename std::remove_cv<T>::type>::format();
     }
@@ -517,7 +517,7 @@ struct is_pod_struct {
            !std::is_same<typename std::remove_cv<T>::type, std::complex<double>>::value };
 };
 
-template <typename T> struct npy_format_descriptor<T, typename std::enable_if<std::is_integral<T>::value>::type> {
+template <typename T> struct npy_format_descriptor<T, enable_if_t<std::is_integral<T>::value>> {
 private:
     constexpr static const int values[8] = {
         npy_api::NPY_BYTE_, npy_api::NPY_UBYTE_, npy_api::NPY_SHORT_,    npy_api::NPY_USHORT_,
@@ -529,13 +529,13 @@ public:
             return object(ptr, true);
         pybind11_fail("Unsupported buffer format!");
     }
-    template <typename T2 = T, typename std::enable_if<std::is_signed<T2>::value, int>::type = 0>
+    template <typename T2 = T, enable_if_t<std::is_signed<T2>::value, int> = 0>
     static PYBIND11_DESCR name() { return _("int") + _<sizeof(T)*8>(); }
-    template <typename T2 = T, typename std::enable_if<!std::is_signed<T2>::value, int>::type = 0>
+    template <typename T2 = T, enable_if_t<!std::is_signed<T2>::value, int> = 0>
     static PYBIND11_DESCR name() { return _("uint") + _<sizeof(T)*8>(); }
 };
 template <typename T> constexpr const int npy_format_descriptor<
-    T, typename std::enable_if<std::is_integral<T>::value>::type>::values[8];
+    T, enable_if_t<std::is_integral<T>::value>>::values[8];
 
 #define DECL_FMT(Type, NumPyName, Name) template<> struct npy_format_descriptor<Type> { \
     enum { value = npy_api::NumPyName }; \
@@ -568,7 +568,7 @@ struct field_descriptor {
 };
 
 template <typename T>
-struct npy_format_descriptor<T, typename std::enable_if<is_pod_struct<T>::value>::type> {
+struct npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>> {
     static PYBIND11_DESCR name() { return _("struct"); }
 
     static pybind11::dtype dtype() {
@@ -634,9 +634,9 @@ private:
 };
 
 template <typename T>
-std::string npy_format_descriptor<T, typename std::enable_if<is_pod_struct<T>::value>::type>::format_str;
+std::string npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>>::format_str;
 template <typename T>
-PyObject* npy_format_descriptor<T, typename std::enable_if<is_pod_struct<T>::value>::type>::dtype_ptr = nullptr;
+PyObject* npy_format_descriptor<T, enable_if_t<is_pod_struct<T>::value>>::dtype_ptr = nullptr;
 
 // Extract name, offset and format descriptor for a struct field
 #define PYBIND11_FIELD_DESCRIPTOR(Type, Field) \

include/pybind11/operators.h

@@ -10,7 +10,6 @@
 #pragma once
 
 #include "pybind11.h"
-#include <type_traits>
 
 #if defined(__clang__) && !defined(__INTEL_COMPILER)
 #  pragma clang diagnostic ignored "-Wunsequenced" // multiple unsequenced modifications to 'self' (when using def(py::self OP Type()))

include/pybind11/pybind11.h

@@ -17,6 +17,7 @@
 #  pragma warning(disable: 4512) // warning C4512: Assignment operator was implicitly defined as deleted
 #  pragma warning(disable: 4800) // warning C4800: 'int': forcing value to bool 'true' or 'false' (performance warning)
 #  pragma warning(disable: 4996) // warning C4996: The POSIX name for this item is deprecated. Instead, use the ISO C and C++ conformant name
+#  pragma warning(disable: 4702) // warning C4702: unreachable code
 #elif defined(__INTEL_COMPILER)
 #  pragma warning(push)
 #  pragma warning(disable: 186)   // pointless comparison of unsigned integer with zero
@@ -460,8 +461,10 @@ protected:
             if (overloads->is_operator)
                 return handle(Py_NotImplemented).inc_ref().ptr();
 
-            std::string msg = "Incompatible " + std::string(overloads->is_constructor ? "constructor" : "function") +
-                              " arguments. The following argument types are supported:\n";
+            std::string msg = std::string(overloads->name) + "(): incompatible " +
+                std::string(overloads->is_constructor ? "constructor" : "function") +
+                " arguments. The following argument types are supported:\n";
+
             int ctr = 0;
             for (detail::function_record *it2 = overloads; it2 != nullptr; it2 = it2->next) {
                 msg += "    "+ std::to_string(++ctr) + ". ";
@@ -489,7 +492,7 @@ protected:
 
                 msg += "\n";
             }
-            msg += "    Invoked with: ";
+            msg += "\nInvoked with: ";
             tuple args_(args, true);
             for (size_t ti = overloads->is_constructor ? 1 : 0; ti < args_.size(); ++ti) {
                 msg += static_cast<std::string>(static_cast<object>(args_[ti]).str());
@@ -574,18 +577,6 @@ public:
     PYBIND11_OBJECT_DEFAULT(generic_type, object, PyType_Check)
 protected:
     void initialize(type_record *rec) {
-        if (rec->base_type) {
-            if (rec->base_handle)
-                pybind11_fail("generic_type: specified base type multiple times!");
-            rec->base_handle = detail::get_type_handle(*(rec->base_type));
-            if (!rec->base_handle) {
-                std::string tname(rec->base_type->name());
-                detail::clean_type_id(tname);
-                pybind11_fail("generic_type: type \"" + std::string(rec->name) +
-                              "\" referenced unknown base type \"" + tname + "\"");
-            }
-        }
-
         auto &internals = get_internals();
         auto tindex = std::type_index(*(rec->type));
 
@@ -615,6 +606,12 @@ protected:
             ht_qualname = name;
         }
 #endif
+
+        size_t num_bases = rec->bases.size();
+        tuple bases(num_bases);
+        for (size_t i = 0; i < num_bases; ++i)
+            bases[i] = rec->bases[i];
+
         std::string full_name = (scope_module ? ((std::string) scope_module.str() + "." + rec->name)
                                               : std::string(rec->name));
 
@@ -627,11 +624,16 @@ protected:
             memcpy((void *) tp_doc, rec->doc, size);
         }
 
+        /* Danger zone: from now (and until PyType_Ready), make sure to
+           issue no Python C API calls which could potentially invoke the
+           garbage collector (the GC will call type_traverse(), which will in
+           turn find the newly constructed type in an invalid state) */
+
         object type_holder(PyType_Type.tp_alloc(&PyType_Type, 0), false);
         auto type = (PyHeapTypeObject*) type_holder.ptr();
 
         if (!type_holder || !name)
-            pybind11_fail("generic_type: unable to create type object!");
+            pybind11_fail(std::string(rec->name) + ": Unable to create type object!");
 
         /* Register supplemental type information in C++ dict */
         detail::type_info *tinfo = new detail::type_info();
@@ -644,8 +646,12 @@ protected:
         /* Basic type attributes */
         type->ht_type.tp_name = strdup(full_name.c_str());
         type->ht_type.tp_basicsize = (ssize_t) rec->instance_size;
-        type->ht_type.tp_base = (PyTypeObject *) rec->base_handle.ptr();
-        rec->base_handle.inc_ref();
+
+        if (num_bases > 0) {
+            type->ht_type.tp_base = (PyTypeObject *) ((object) bases[0]).inc_ref().ptr();
+            type->ht_type.tp_bases = bases.release().ptr();
+            rec->multiple_inheritance |= num_bases > 1;
+        }
 
         type->ht_name = name.release().ptr();
 
@@ -676,7 +682,8 @@ protected:
         type->ht_type.tp_doc = tp_doc;
 
         if (PyType_Ready(&type->ht_type) < 0)
-            pybind11_fail("generic_type: PyType_Ready failed!");
+            pybind11_fail(std::string(rec->name) + ": PyType_Ready failed (" +
+                          detail::error_string() + ")!");
 
         m_ptr = type_holder.ptr();
 
@@ -687,9 +694,23 @@ protected:
         if (rec->scope)
             rec->scope.attr(handle(type->ht_name)) = *this;
 
+        if (rec->multiple_inheritance)
+            mark_parents_nonsimple(&type->ht_type);
+
         type_holder.release();
     }
 
+    /// Helper function which tags all parents of a type using mult. inheritance
+    void mark_parents_nonsimple(PyTypeObject *value) {
+        tuple t(value->tp_bases, true);
+        for (handle h : t) {
+            auto tinfo2 = get_type_info((PyTypeObject *) h.ptr());
+            if (tinfo2)
+                tinfo2->simple_type = false;
+            mark_parents_nonsimple((PyTypeObject *) h.ptr());
+        }
+    }
+
     /// Allocate a metaclass on demand (for static properties)
     handle metaclass() {
         auto &ht_type = ((PyHeapTypeObject *) m_ptr)->ht_type;
@@ -809,31 +830,18 @@ protected:
     static void releasebuffer(PyObject *, Py_buffer *view) { delete (buffer_info *) view->internal; }
 };
 
-template <template<typename> class Predicate, typename... BaseTypes> struct class_selector;
-template <template<typename> class Predicate, typename Base, typename... Bases>
-struct class_selector<Predicate, Base, Bases...> {
-    static inline void set_bases(detail::type_record &record) {
-        if (Predicate<Base>::value) record.base_type = &typeid(Base);
-        else class_selector<Predicate, Bases...>::set_bases(record);
-    }
-};
-template <template<typename> class Predicate>
-struct class_selector<Predicate> {
-    static inline void set_bases(detail::type_record &) {}
-};
-
 NAMESPACE_END(detail)
 
 template <typename type_, typename... options>
 class class_ : public detail::generic_type {
     template <typename T> using is_holder = detail::is_holder_type<type_, T>;
     template <typename T> using is_subtype = detail::bool_constant<std::is_base_of<type_, T>::value && !std::is_same<T, type_>::value>;
-    template <typename T> using is_base_class = detail::bool_constant<std::is_base_of<T, type_>::value && !std::is_same<T, type_>::value>;
+    template <typename T> using is_base = detail::bool_constant<std::is_base_of<T, type_>::value && !std::is_same<T, type_>::value>;
     template <typename T> using is_valid_class_option =
         detail::bool_constant<
             is_holder<T>::value ||
             is_subtype<T>::value ||
-            is_base_class<T>::value
+            is_base<T>::value
         >;
 
 public:
@@ -846,9 +854,6 @@ public:
     static_assert(detail::all_of_t<is_valid_class_option, options...>::value,
             "Unknown/invalid class_ template parameters provided");
 
-    static_assert(detail::count_t<is_base_class, options...>::value <= 1,
-            "Invalid class_ base types: multiple inheritance is not supported");
-
     PYBIND11_OBJECT(class_, detail::generic_type, PyType_Check)
 
     template <typename... Extra>
@@ -862,7 +867,9 @@ public:
         record.init_holder = init_holder;
         record.dealloc = dealloc;
 
-        detail::class_selector<is_base_class, options...>::set_bases(record);
+        /* Register base classes specified via template arguments to class_, if any */
+        bool unused[] = { (add_base<options>(record), false)..., false };
+        (void) unused;
 
         /* Process optional arguments, if any */
         detail::process_attributes<Extra...>::init(extra..., &record);
@@ -875,6 +882,16 @@ public:
         }
     }
 
+    template <typename Base, detail::enable_if_t<is_base<Base>::value, int> = 0>
+    static void add_base(detail::type_record &rec) {
+        rec.add_base(&typeid(Base), [](void *src) -> void * {
+            return static_cast<Base *>(reinterpret_cast<type *>(src));
+        });
+    }
+
+    template <typename Base, detail::enable_if_t<!is_base<Base>::value, int> = 0>
+    static void add_base(detail::type_record &) { }
+
     template <typename Func, typename... Extra>
     class_ &def(const char *name_, Func&& f, const Extra&... extra) {
         cpp_function cf(std::forward<Func>(f), name(name_),
@@ -1016,7 +1033,7 @@ private:
 
     /// Initialize holder object, variant 2: try to construct from existing holder object, if possible
     template <typename T = holder_type,
-              typename std::enable_if<std::is_copy_constructible<T>::value, int>::type = 0>
+              detail::enable_if_t<std::is_copy_constructible<T>::value, int> = 0>
     static void init_holder_helper(instance_type *inst, const holder_type *holder_ptr, const void * /* dummy */) {
         if (holder_ptr)
             new (&inst->holder) holder_type(*holder_ptr);
@@ -1026,7 +1043,7 @@ private:
 
     /// Initialize holder object, variant 3: holder is not copy constructible (e.g. unique_ptr), always initialize from raw pointer
     template <typename T = holder_type,
-              typename std::enable_if<!std::is_copy_constructible<T>::value, int>::type = 0>
+              detail::enable_if_t<!std::is_copy_constructible<T>::value, int> = 0>
     static void init_holder_helper(instance_type *inst, const holder_type * /* unused */, const void * /* dummy */) {
         new (&inst->holder) holder_type(inst->value);
     }
@@ -1196,7 +1213,7 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
 iterator make_iterator(Iterator first, Sentinel last, Extra &&... extra) {
     typedef detail::iterator_state<Iterator, Sentinel, false, Policy> state;
 
-    if (!detail::get_type_info(typeid(state))) {
+    if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator")
             .def("__iter__", [](state &s) -> state& { return s; })
             .def("__next__", [](state &s) -> ValueType {
@@ -1221,7 +1238,7 @@ template <return_value_policy Policy = return_value_policy::reference_internal,
 iterator make_key_iterator(Iterator first, Sentinel last, Extra &&... extra) {
     typedef detail::iterator_state<Iterator, Sentinel, true, Policy> state;
 
-    if (!detail::get_type_info(typeid(state))) {
+    if (!detail::get_type_info(typeid(state), false)) {
         class_<state>(handle(), "iterator")
             .def("__iter__", [](state &s) -> state& { return s; })
             .def("__next__", [](state &s) -> KeyType {

include/pybind11/pytypes.h

@@ -43,10 +43,8 @@ public:
     bool is_none() const { return m_ptr == Py_None; }
     template <typename T> T cast() const;
     template <return_value_policy policy = return_value_policy::automatic_reference, typename ... Args>
-    #if __cplusplus > 201103L
-    [[deprecated("call(...) was deprecated in favor of operator()(...)")]]
-    #endif
-    object call(Args&&... args) const;
+    PYBIND11_DEPRECATED("call(...) was deprecated in favor of operator()(...)")
+        object call(Args&&... args) const;
     template <return_value_policy policy = return_value_policy::automatic_reference, typename ... Args>
     object operator()(Args&&... args) const;
     operator bool() const { return m_ptr != nullptr; }
@@ -492,7 +490,7 @@ class int_ : public object {
 public:
     PYBIND11_OBJECT_DEFAULT(int_, object, PYBIND11_LONG_CHECK)
     template <typename T,
-              typename std::enable_if<std::is_integral<T>::value, int>::type = 0>
+              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     int_(T value) {
         if (sizeof(T) <= sizeof(long)) {
             if (std::is_signed<T>::value)
@@ -509,7 +507,7 @@ public:
     }
 
     template <typename T,
-              typename std::enable_if<std::is_integral<T>::value, int>::type = 0>
+              detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     operator T() const {
         if (sizeof(T) <= sizeof(long)) {
             if (std::is_signed<T>::value)
@@ -614,7 +612,7 @@ public:
     }
     size_t size() const { return (size_t) PyList_Size(m_ptr); }
     detail::list_accessor operator[](size_t index) const { return detail::list_accessor(*this, index); }
-    void append(const object &object) const { PyList_Append(m_ptr, object.ptr()); }
+    void append(handle h) const { PyList_Append(m_ptr, h.ptr()); }
 };
 
 class args : public tuple { PYBIND11_OBJECT_DEFAULT(args, tuple, PyTuple_Check) };

include/pybind11/stl.h

@@ -112,7 +112,7 @@ template <typename Type, typename Value> struct list_caster {
     }
 
     template <typename T = Type,
-              typename std::enable_if<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int>::type = 0>
+              enable_if_t<std::is_same<decltype(std::declval<T>().reserve(0)), void>::value, int> = 0>
     void reserve_maybe(list l, Type *) { value.reserve(l.size()); }
     void reserve_maybe(list, void *) { }
 

include/pybind11/stl_bind.h

@@ -12,8 +12,6 @@
 #include "common.h"
 #include "operators.h"
 
-#include <type_traits>
-#include <utility>
 #include <algorithm>
 #include <sstream>
 
@@ -42,20 +40,20 @@ struct is_comparable : std::false_type { };
 /* For non-map data structures, check whether operator== can be instantiated */
 template <typename T>
 struct is_comparable<
-    T, typename std::enable_if<container_traits<T>::is_element &&
-                               container_traits<T>::is_comparable>::type>
+    T, enable_if_t<container_traits<T>::is_element &&
+                   container_traits<T>::is_comparable>>
     : std::true_type { };
 
 /* For a vector/map data structure, recursively check the value type (which is std::pair for maps) */
 template <typename T>
-struct is_comparable<T, typename std::enable_if<container_traits<T>::is_vector>::type> {
+struct is_comparable<T, enable_if_t<container_traits<T>::is_vector>> {
     static constexpr const bool value =
         is_comparable<typename T::value_type>::value;
 };
 
 /* For pairs, recursively check the two data types */
 template <typename T>
-struct is_comparable<T, typename std::enable_if<container_traits<T>::is_pair>::type> {
+struct is_comparable<T, enable_if_t<container_traits<T>::is_pair>> {
     static constexpr const bool value =
         is_comparable<typename T::first_type>::value &&
         is_comparable<typename T::second_type>::value;
@@ -66,13 +64,13 @@ template <typename, typename, typename... Args> void vector_if_copy_constructibl
 template <typename, typename, typename... Args> void vector_if_equal_operator(const Args&...) { }
 template <typename, typename, typename... Args> void vector_if_insertion_operator(const Args&...) { }
 
-template<typename Vector, typename Class_, typename std::enable_if<std::is_copy_constructible<typename Vector::value_type>::value, int>::type = 0>
+template<typename Vector, typename Class_, enable_if_t<std::is_copy_constructible<typename Vector::value_type>::value, int> = 0>
 void vector_if_copy_constructible(Class_ &cl) {
     cl.def(pybind11::init<const Vector &>(),
            "Copy constructor");
 }
 
-template<typename Vector, typename Class_, typename std::enable_if<is_comparable<Vector>::value, int>::type = 0>
+template<typename Vector, typename Class_, enable_if_t<is_comparable<Vector>::value, int> = 0>
 void vector_if_equal_operator(Class_ &cl) {
     using T = typename Vector::value_type;
 
@@ -378,7 +376,7 @@ template <typename Map, typename Class_, typename... Args> void map_if_copy_assi
     );
 }
 
-template<typename Map, typename Class_, typename std::enable_if<!std::is_copy_assignable<typename Map::mapped_type>::value, int>::type = 0>
+template<typename Map, typename Class_, enable_if_t<!std::is_copy_assignable<typename Map::mapped_type>::value, int> = 0>
 void map_if_copy_assignable(Class_ &cl) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;

tests/CMakeLists.txt

@@ -29,9 +29,9 @@ set(PYBIND11_TEST_FILES
   test_pickling.cpp
   test_python_types.cpp
   test_sequences_and_iterators.cpp
-  test_smart_ptr.cpp
   test_stl_binders.cpp
   test_virtual_functions.cpp
+  test_multiple_inheritance.cpp
 )
 
 string(REPLACE ".cpp" ".py" PYBIND11_PYTEST_FILES "${PYBIND11_TEST_FILES}")

tests/test_callbacks.py

@@ -83,7 +83,7 @@ def test_cpp_function_roundtrip():
 
     with pytest.raises(TypeError) as excinfo:
         test_dummy_function(dummy_function2)
-    assert "Incompatible function arguments" in str(excinfo.value)
+    assert "incompatible function arguments" in str(excinfo.value)
 
     with pytest.raises(TypeError) as excinfo:
         test_dummy_function(lambda x, y: x + y)

tests/test_inheritance.cpp

@@ -61,7 +61,7 @@ test_initializer inheritance([](py::module &m) {
         .def(py::init<std::string>());
 
     /* Another way of declaring a subclass relationship: reference parent's C++ type */
-    py::class_<Rabbit>(m, "Rabbit", py::base<Pet>())
+    py::class_<Rabbit, Pet>(m, "Rabbit")
         .def(py::init<std::string>());
 
     /* And another: list parent in class template arguments */

tests/test_inheritance.py

@@ -24,9 +24,10 @@ def test_inheritance(msg):
     with pytest.raises(TypeError) as excinfo:
         dog_bark(polly)
     assert msg(excinfo.value) == """
-        Incompatible function arguments. The following argument types are supported:
+        dog_bark(): incompatible function arguments. The following argument types are supported:
             1. (arg0: m.Dog) -> str
-            Invoked with: <m.Pet object at 0>
+
+        Invoked with: <m.Pet object at 0>
     """