Respect alignment of by-value storage.

test/Jamfile

@@ -132,6 +132,7 @@ bpl-test crossmod_exception
 
 [ bpl-test object ]
 [ bpl-test class ]
+[ bpl-test aligned_class ]
 [ bpl-test list ]
 [ bpl-test long ]
 [ bpl-test dict ]

test/aligned_class.cpp

@@ -0,0 +1,33 @@
+// Distributed under the Boost Software License, Version 1.0. (See
+// accompanying file LICENSE_1_0.txt or copy at
+// http://www.boost.org/LICENSE_1_0.txt)
+#include <boost/python/module.hpp>
+#include <boost/python/def.hpp>
+#include <boost/python/object.hpp>
+#include <boost/python/class.hpp>
+#include <boost/assert.hpp>
+#include <boost/cstdint.hpp>
+
+using namespace boost::python;
+
+struct BOOST_ALIGNMENT(32) X
+{
+    int x;
+    BOOST_ALIGNMENT(32) float f;
+    X(int n, float _f) : x(n), f(_f)
+    {
+        BOOST_ASSERT((reinterpret_cast<uintptr_t>(&f) % 32) == 0);
+    }
+};
+
+int x_function(X& x) { return x.x;}
+float f_function(X& x) { return x.f;}
+
+BOOST_PYTHON_MODULE(aligned_class_ext)
+{
+    class_<X>("X", init<int, float>());
+    def("x_function", x_function);
+    def("f_function", f_function);
+}
+
+#include "module_tail.cpp"

test/aligned_class.py

@@ -0,0 +1,44 @@
+# Distributed under the Boost
+# Software License, Version 1.0. (See accompanying
+# file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+'''
+>>> from aligned_class_ext import *
+
+Ensure sanity:
+
+    >>> x = X(42, 16)
+    >>> x_function(x)
+    42
+    >>> f_function(x)
+    16.0
+
+Demonstrate extraction in the presence of metaclass changes:
+
+    >>> class MetaX(X.__class__):
+    ...     def __new__(cls, *args):
+    ...         return super(MetaX, cls).__new__(cls, *args)
+    >>> class XPlusMetatype(X):
+    ...     __metaclass__ = MetaX
+    >>> x = XPlusMetatype(42, 16)
+    >>> x_function(x)
+    42
+    >>> f_function(x)
+    16.0
+
+
+'''
+
+def run(args = None):
+    import sys
+    import doctest
+
+    if args is not None:
+        sys.argv = args
+    return doctest.testmod(sys.modules.get(__name__))
+
+if __name__ == '__main__':
+    print("running...")
+    import sys
+    status = run()[0]
+    if (status == 0): print("Done.")
+    sys.exit(status)

test/fabscript

@@ -79,6 +79,8 @@ for t in [('injected',),
           ('callbacks',),
           ('defaults',),
           ('object',),
+          ('class',),
+          ('aligned_class',),
           ('list',),
           ('long',),
           ('dict',),