Avoid copying C++ classes when passing constructor arguments.

Cython/Compiler/ModuleNode.py

@@ -905,7 +905,7 @@ class ModuleNode(Nodes.Node, Nodes.BlockNode):
                 if constructor:
                     arg_decls = []
                     arg_names = []
-                    for arg in constructor.type.args[:len(constructor.type.args)-constructor.type.optional_arg_count]:
+                    for arg in constructor.type.original_args[:len(constructor.type.args)-constructor.type.optional_arg_count]:
                         arg_decls.append(arg.declaration_code())
                         arg_names.append(arg.cname)
                     if constructor.type.optional_arg_count:

Cython/Compiler/Symtab.py

@@ -2311,6 +2311,16 @@ class CppClassScope(Scope):
             cname = "%s__init__%s" % (Naming.func_prefix, class_name)
             name = '<init>'
             type.return_type = PyrexTypes.CVoidType()
+            # This is called by the actual constructor, but need to support
+            # arguments that cannot by called by value.
+            type.original_args = type.args
+            def maybe_ref(arg):
+                if arg.type.is_cpp_class and not arg.type.is_reference:
+                    return PyrexTypes.CFuncTypeArg(
+                        arg.name, PyrexTypes.c_ref_type(arg.type), arg.pos)
+                else:
+                    return arg
+            type.args = [maybe_ref(arg) for arg in type.args]
         elif name == '__dealloc__' and cname is None:
             cname = "%s__dealloc__%s" % (Naming.func_prefix, class_name)
             name = '<del>'

tests/run/cpp_classes_def.pyx

@@ -6,6 +6,7 @@ cdef double pi
 from math import pi
 from libc.math cimport sin, cos
 from libcpp cimport bool
+from libcpp.memory cimport unique_ptr
 from libcpp.vector cimport vector
 from cython.operator cimport dereference as deref
 
@@ -222,3 +223,17 @@ def test_CppClassWithObjectMemberCopyAssign(name):
     print "Alive in vector", v[0].o
     v.clear()
     print "Nothing alive."
+
+
+cdef cppclass UncopyableConstructorArgument:
+    unique_ptr[vector[int]] member
+    __init__(unique_ptr[vector[int]] arg):
+        this.member.reset(arg.release())
+
+def test_uncopyable_constructor_argument():
+    """
+    >>> test_uncopyable_constructor_argument()
+    """
+    cdef UncopyableConstructorArgument *c = new UncopyableConstructorArgument(
+        unique_ptr[vector[int]](new vector[int]()))
+    del c