Hello! I've encountered some behavior in C-FFI that I would like to discuss.<br>
When you try to define an enumeration containing duplicate values, C-FFI gives the error:<br>
<br>
&quot;A foreign enum cannot contain duplicate values: 0.&quot;<br>
<br>
However, C enumerations can contain duplicate values, and this feature is used by real code. FLTK, for example,<br>
uses it to provide for source compatibility when the name of enumeration elements are changed. Without direct<br>
C-FFI support for this feature, the resultant C-FFI bindings do not translate well to what the user expects (enumeration<br>
keys available in the C header are not available in the Lisp binding). <br>
<br>
Verrazano works around this issue right now (by discarding duplicate keys), but it's a sub-optimal solution,<br>
since there is no way to programatically determine a consistent set of keys to discard. For example,<br>
FLTK contains an enumeration in which FL_ALIGN_TOP_LEFT and FL_ALIGN_LEFT_TOP alias each other, <br>
and FL_ALIGN_TOP_RIGHT FL_ALIGN_RIGHT_TOP alias each other. Depending on the ordering in the header file,<br>
the enumeration may end up containing an inconsistent set of names (eg: FL_ALIGN_TOP_LEFT and FL_ALIGN_RIGHT_TOP).<br>
<br>
Sincerely,<br>
&nbsp;&nbsp;&nbsp; Rayiner Hashem<br>