Update enum_ and bind_vector to new-style init and pickle

Fixes #1046.

include/pybind11/pybind11.h

@@ -1313,6 +1313,30 @@ private:
     }
 };
 
+/// Binds an existing constructor taking arguments Args...
+template <typename... Args> detail::initimpl::constructor<Args...> init() { return {}; }
+/// Like `init<Args...>()`, but the instance is always constructed through the alias class (even
+/// when not inheriting on the Python side).
+template <typename... Args> detail::initimpl::alias_constructor<Args...> init_alias() { return {}; }
+
+/// Binds a factory function as a constructor
+template <typename Func, typename Ret = detail::initimpl::factory<Func>>
+Ret init(Func &&f) { return {std::forward<Func>(f)}; }
+
+/// Dual-argument factory function: the first function is called when no alias is needed, the second
+/// when an alias is needed (i.e. due to python-side inheritance).  Arguments must be identical.
+template <typename CFunc, typename AFunc, typename Ret = detail::initimpl::factory<CFunc, AFunc>>
+Ret init(CFunc &&c, AFunc &&a) {
+    return {std::forward<CFunc>(c), std::forward<AFunc>(a)};
+}
+
+/// Binds pickling functions `__getstate__` and `__setstate__` and ensures that the type
+/// returned by `__getstate__` is the same as the argument accepted by `__setstate__`.
+template <typename GetState, typename SetState>
+detail::initimpl::pickle_factory<GetState, SetState> pickle(GetState &&g, SetState &&s) {
+    return {std::forward<GetState>(g), std::forward<SetState>(s)};
+};
+
 /// Binds C++ enumerations and enumeration classes to Python
 template <typename Type> class enum_ : public class_<Type> {
 public:
@@ -1340,7 +1364,7 @@ public:
                 m[kv.first] = kv.second;
             return m;
         }, return_value_policy::copy);
-        def("__init__", [](Type& value, Scalar i) { value = (Type)i; });
+        def(init([](Scalar i) { return static_cast<Type>(i); }));
         def("__int__", [](Type value) { return (Scalar) value; });
         #if PY_MAJOR_VERSION < 3
             def("__long__", [](Type value) { return (Scalar) value; });
@@ -1378,8 +1402,8 @@ public:
         }
         def("__hash__", [](const Type &value) { return (Scalar) value; });
         // Pickling and unpickling -- needed for use with the 'multiprocessing' module
-        def("__getstate__", [](const Type &value) { return pybind11::make_tuple((Scalar) value); });
-        def("__setstate__", [](Type &p, tuple t) { new (&p) Type((Type) t[0].cast<Scalar>()); });
+        def(pickle([](const Type &value) { return pybind11::make_tuple((Scalar) value); },
+                   [](tuple t) { return static_cast<Type>(t[0].cast<Scalar>()); }));
     }
 
     /// Export enumeration entries into the parent scope
@@ -1402,30 +1426,6 @@ private:
     handle m_parent;
 };
 
-/// Binds an existing constructor taking arguments Args...
-template <typename... Args> detail::initimpl::constructor<Args...> init() { return {}; }
-/// Like `init<Args...>()`, but the instance is always constructed through the alias class (even
-/// when not inheriting on the Python side).
-template <typename... Args> detail::initimpl::alias_constructor<Args...> init_alias() { return {}; }
-
-/// Binds a factory function as a constructor
-template <typename Func, typename Ret = detail::initimpl::factory<Func>>
-Ret init(Func &&f) { return {std::forward<Func>(f)}; }
-
-/// Dual-argument factory function: the first function is called when no alias is needed, the second
-/// when an alias is needed (i.e. due to python-side inheritance).  Arguments must be identical.
-template <typename CFunc, typename AFunc, typename Ret = detail::initimpl::factory<CFunc, AFunc>>
-Ret init(CFunc &&c, AFunc &&a) {
-    return {std::forward<CFunc>(c), std::forward<AFunc>(a)};
-}
-
-/// Binds pickling functions `__getstate__` and `__setstate__` and ensures that the type
-/// returned by `__getstate__` is the same as the argument accepted by `__setstate__`.
-template <typename GetState, typename SetState>
-detail::initimpl::pickle_factory<GetState, SetState> pickle(GetState &&g, SetState &&s) {
-    return {std::forward<GetState>(g), std::forward<SetState>(s)};
-};
-
 NAMESPACE_BEGIN(detail)
 
 

include/pybind11/stl_bind.h

@@ -120,17 +120,13 @@ void vector_modifiers(enable_if_t<is_copy_constructible<typename Vector::value_t
            arg("x"),
            "Add an item to the end of the list");
 
-    cl.def("__init__", [](Vector &v, iterable it) {
-        new (&v) Vector();
-        try {
-            v.reserve(len(it));
-            for (handle h : it)
-               v.push_back(h.cast<T>());
-        } catch (...) {
-            v.~Vector();
-            throw;
-        }
-    });
+    cl.def(init([](iterable it) {
+        auto v = std::unique_ptr<Vector>(new Vector());
+        v->reserve(len(it));
+        for (handle h : it)
+           v->push_back(h.cast<T>());
+        return v.release();
+    }));
 
     cl.def("extend",
        [](Vector &v, const Vector &src) {
@@ -346,20 +342,22 @@ vector_buffer(Class_& cl) {
         return buffer_info(v.data(), static_cast<ssize_t>(sizeof(T)), format_descriptor<T>::format(), 1, {v.size()}, {sizeof(T)});
     });
 
-    cl.def("__init__", [](Vector& vec, buffer buf) {
+    cl.def(init([](buffer buf) {
         auto info = buf.request();
         if (info.ndim != 1 || info.strides[0] % static_cast<ssize_t>(sizeof(T)))
             throw type_error("Only valid 1D buffers can be copied to a vector");
         if (!detail::compare_buffer_info<T>::compare(info) || (ssize_t) sizeof(T) != info.itemsize)
             throw type_error("Format mismatch (Python: " + info.format + " C++: " + format_descriptor<T>::format() + ")");
-        new (&vec) Vector();
-        vec.reserve((size_t) info.shape[0]);
+
+        auto vec = std::unique_ptr<Vector>(new Vector());
+        vec->reserve((size_t) info.shape[0]);
         T *p = static_cast<T*>(info.ptr);
         ssize_t step = info.strides[0] / static_cast<ssize_t>(sizeof(T));
         T *end = p + info.shape[0] * step;
         for (; p != end; p += step)
-            vec.push_back(*p);
-    });
+            vec->push_back(*p);
+        return vec.release();
+    }));
 
     return;
 }

tests/test_buffers.cpp

@@ -78,13 +78,15 @@ TEST_SUBMODULE(buffers, m) {
     py::class_<Matrix>(m, "Matrix", py::buffer_protocol())
         .def(py::init<ssize_t, ssize_t>())
         /// Construct from a buffer
-        .def("__init__", [](Matrix &v, py::buffer b) {
+        .def(py::init([](py::buffer b) {
             py::buffer_info info = b.request();
             if (info.format != py::format_descriptor<float>::format() || info.ndim != 2)
                 throw std::runtime_error("Incompatible buffer format!");
-            new (&v) Matrix(info.shape[0], info.shape[1]);
-            memcpy(v.data(), info.ptr, sizeof(float) * (size_t) (v.rows() * v.cols()));
-        })
+
+            auto v = new Matrix(info.shape[0], info.shape[1]);
+            memcpy(v->data(), info.ptr, sizeof(float) * (size_t) (v->rows() * v->cols()));
+            return v;
+        }))
 
        .def("rows", &Matrix::rows)
        .def("cols", &Matrix::cols)