Add comments about C11 generic

Author: sim642

src/frontc/cabs.ml

@@ -80,7 +80,7 @@ type typeSpecifier = (* Merge all specifiers into one type *)
   | Tenum of string * enum_item list option * attribute list
   | TtypeofE of expression                      (* GCC __typeof__ *)
   | TtypeofT of specifier * decl_type       (* GCC __typeof__ *)
-  | Tdefault
+  | Tdefault (** "default" in generic associations *)
 
 and storage =
     NO_STORAGE | AUTO | STATIC | EXTERN | REGISTER

src/frontc/cabs2cil.ml

@@ -4857,6 +4857,9 @@ and doExp (asconst: bool)   (* This expression is used as a constant *)
           | _ -> true
           | exception (Failure _) -> false
         in
+        (* cppreference mentions "lvalue conversions" on e before compatibility: https://en.cppreference.com/w/c/language/generic.
+           C11 standard section 6.5.1.1.3 does not mention anything.
+           TODO: Which is it and does doExp already do this? *)
         let (_, _, e_typ) = doExp false e (AExp None) in
         let al_compatible = List.filter (fun (at, _) -> typ_compatible e_typ (doOnlyType at JUSTBASE)) al_nondefault in
 

src/frontc/cprint.ml

@@ -196,7 +196,7 @@ and print_type_spec = function
       (print_enum_items enum_items)
   | TtypeofE e -> printl ["__typeof__";"("]; print_expression e; print ") "
   | TtypeofT (s,d) -> printl ["__typeof__";"("]; print_onlytype (s, d); print ") "
-  | Tdefault -> print "default "
+  | Tdefault -> print "default " (* TODO: is this right? *)
 
 
 (* print "struct foo", but with specified keyword and a list of
@@ -404,7 +404,7 @@ and get_operator exp =
   | TYPE_SIZEOF _ -> ("", 16)
   | EXPR_ALIGNOF exp -> ("", 16)
   | TYPE_ALIGNOF _ -> ("", 16)
-  | GENERIC _ -> ("", 16)
+  | GENERIC _ -> ("", 16) (* TODO: is this right? *)
   | IMAG exp -> ("", 16)
   | REAL exp -> ("", 16)
   | CLASSIFYTYPE exp -> ("", 16)
@@ -541,6 +541,7 @@ and print_expression_level (lvl: int) (exp : expression) =
       print_onlytype (bt, dt);
       print ")"
   | GENERIC (exp, lst) -> 
+      (* TODO: is this right? *)
       let print_generic_list l =
         match l with 
         [] -> ()