core: add alignment value automatically deduced

include/eigenpy/register.hpp

@@ -79,6 +79,7 @@ namespace eigenpy
     static int registerNewType(PyTypeObject * py_type_ptr,
                                const std::type_info * type_info_ptr,
                                const int type_size,
+                               const int alignment,
                                PyArray_GetItemFunc * getitem,
                                PyArray_SetItemFunc * setitem,
                                PyArray_NonzeroFunc * nonzero,

include/eigenpy/user-type.hpp

@@ -27,6 +27,18 @@ namespace eigenpy
 //      static void cast(void * /*from*/, void * /*to*/, npy_intp /*n*/, void * /*fromarr*/, void * /*toarr*/) {};
     };
   
+    template<typename T>
+    struct OffsetOf
+    {
+      struct Data
+      {
+        char c;
+        T v;
+      };
+      
+      enum { value = offsetof(Data, v) };
+    };
+  
     template<typename T>
     struct SpecialMethods<T,NPY_USERDEF>
     {
@@ -194,6 +206,7 @@ namespace eigenpy
     int code = Register::registerNewType(py_type_ptr,
                                          &typeid(Scalar),
                                          sizeof(Scalar),
+                                         internal::OffsetOf<Scalar>::value,
                                          getitem, setitem, nonzero,
                                          copyswap, copyswapn,
                                          dotfunc);

src/register.cpp

@@ -36,6 +36,7 @@ namespace eigenpy
   int Register::registerNewType(PyTypeObject * py_type_ptr,
                                 const std::type_info * type_info_ptr,
                                 const int type_size,
+                                const int alignement,
                                 PyArray_GetItemFunc * getitem,
                                 PyArray_SetItemFunc * setitem,
                                 PyArray_NonzeroFunc * nonzero,
@@ -68,7 +69,7 @@ namespace eigenpy
     descr.type_num = 0;
     descr.names = 0;
     descr.fields = 0;
-    descr.alignment = call_PyArray_DescrFromType(NPY_OBJECT)->alignment;
+    descr.alignment = alignement; //call_PyArray_DescrFromType(NPY_OBJECT)->alignment;
     
     PyArray_ArrFuncs * funcs_ptr = new PyArray_ArrFuncs;
     PyArray_ArrFuncs & funcs = *funcs_ptr;