* 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 \a rows field push its value onto the stack, then the \a cols field
* 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 \a rows field push its value onto the stack, then the \a cols field