+ * \warning The mecanism for multidimensional arrays is known to be fragile and cumbersome. If you want to use it,
+ * you have to understand how it is implemented: the multiplication is performed using the sizes stack. In previous example,
+ * a \ref gras_datadesc_cb_push_int callback is added to the \a rows field and a \ref gras_datadesc_cb_push_int_mult one is
+ * added to \a cols. So, when the structure is sent, the rows field push its value onto the stack, then the \a cols field
+ * retrieve this value from the stack, compute (and push) the multiplication value. The \a matrix field can then retrive this
+ * value by poping the array. There is several ways for this to go wrong:
+ * - if the matrix field is placed before the sizes, the right value won't get pushed into the stack soon enough. Reorder your structure fields if needed.
+ * - if you write GRAS_ANNOTE(size,cols*rows); in previous example (inverting rows and cols in annotation),
+ * \a rows will be given a \ref gras_datadesc_cb_push_int_mult. This cannot work since it will try to
+ * pop the value which will be pushed by \a cols <i>afterward</i>.
+ * - if you have more than one matrix in your structure, don't interleave the size. They are pushed/poped in the structure order.
+ * - if some of the sizes are used in more than one matrix, you cannot use this mecanism -- sorry.
+ *
+ * If you cannot express your datadescs with this mechanism, you'll have to use the more advanced