Distinguish object-related and name-related attributes

This is a second step towards mimicking GCC/Clang's handling of attributes.

This commit introduces a distinction between
- Object-related attributes, such as "section", which apply to the object (function, variable) being defined;
- Name-related attributes, such as "aligned", which apply to the name (object, struct/union member, struct/union/enum tag) being defined.

In particular, "aligned" is now attached to "struct" and "union" definitions, while it used to be "floated up" before.

The C11 _Alignas modifier is treated like an object-related attribute, so that
```
       struct s { ... };
       _Alignas(64) struct s x;
```
correctly associates the alignment with "x" and not with "struct s", where it would be ignored because it was not part of the original definition of s.

4 files changed, 24 insertions, 13 deletions

diff --git a/cfrontend/C2C.ml b/cfrontend/C2C.ml
index d6bf76f3..d70c4dad 100644
--- a/cfrontend/C2C.ml
+++ b/cfrontend/C2C.ml
@@ -315,8 +315,9 @@ let attributes = [
   ("noinline",Cutil.Attr_function);
   (* name-related *)
   ("aligned", Cutil.Attr_name);
-  ("section", Cutil.Attr_name);
-  ("unused", Cutil.Attr_name)
+  (* object-related *)
+  ("section", Cutil.Attr_object);
+  ("unused", Cutil.Attr_object)
 ]
 
 
diff --git a/cparser/Cutil.ml b/cparser/Cutil.ml
index b926e84a..25329694 100644
--- a/cparser/Cutil.ml
+++ b/cparser/Cutil.ml
@@ -95,7 +95,10 @@ let rec remove_custom_attributes (names: string list)  (al: attributes) =
 (* Classification of attributes *)
 
 type attribute_class =
-  | Attr_name           (* Attribute applies to the names being declared  *)
+  | Attr_object         (* Attribute applies to the object being declared
+                           (function, global variable, local variable)  *)
+  | Attr_name           (* Attribute applies to the name being declared
+                          (object, struct/union member, struct/union/enum tag *)
   | Attr_type           (* Attribute applies to types *)
   | Attr_struct         (* Attribute applies to struct, union and enum *)
   | Attr_function       (* Attribute applies to function types and decls *)
@@ -111,7 +114,7 @@ let declare_attributes l =
 
 let class_of_attribute = function
   | AConst | AVolatile | ARestrict -> Attr_type
-  | AAlignas _ -> Attr_name
+  | AAlignas _ -> Attr_object
   | Attr(name, args) ->
       try Hashtbl.find attr_class (normalize_attrname name)
       with Not_found -> Attr_unknown
diff --git a/cparser/Cutil.mli b/cparser/Cutil.mli
index a99bf3af..400a6319 100644
--- a/cparser/Cutil.mli
+++ b/cparser/Cutil.mli
@@ -64,7 +64,10 @@ val has_std_alignas :  Env.t -> typ -> bool
   (* Do the attributes of the type contain the C11 _Alignas attribute *)
 
 type attribute_class =
-  | Attr_name           (* Attribute applies to the names being declared  *)
+  | Attr_object         (* Attribute applies to the object being declared
+                          (function, global variable, local variable)  *)
+  | Attr_name           (* Attribute applies to the name being declared
+                          (object, struct/union member, struct/union/enum tag *)
   | Attr_type           (* Attribute applies to types *)
   | Attr_struct         (* Attribute applies to struct, union and enum *)
   | Attr_function       (* Attribute applies to function types and decls *)
diff --git a/cparser/Elab.ml b/cparser/Elab.ml
index 8f42fe0a..46bc63a9 100644
--- a/cparser/Elab.ml
+++ b/cparser/Elab.ml
@@ -656,15 +656,19 @@ let rec elab_specifier ?(only = false) loc env specifier =
     restrict_check ty;
     (!sto, !inline, !noreturn ,!typedef, add_attributes_type !attr ty, env) in
 
-  (* As done in CIL, partition !attr into struct-related attributes,
+  (* Partition !attr into name- and struct-related attributes,
      which are returned, and other attributes, which are left in !attr.
-     The returned struct-related attributes are applied to the
+     The returned name-or-struct-related attributes are applied to the
      struct/union/enum being defined.
-     The leftover non-struct-related attributes will be applied
+     The leftover attributes (e.g. object attributes) will be applied
      to the variable being defined. *)
-  let get_struct_attrs () =
+  let get_definition_attrs () =
     let (ta, nta) =
-      List.partition (fun a -> class_of_attribute a = Attr_struct) !attr in
+      List.partition
+        (fun a -> match class_of_attribute a with
+                  | Attr_struct | Attr_name -> true
+                  | _ -> false)
+        !attr in
     attr := nta;
     ta in
 
@@ -723,7 +727,7 @@ let rec elab_specifier ?(only = false) loc env specifier =
 
     | [Cabs.Tstruct_union(STRUCT, id, optmembers, a)] ->
         let a' =
-          add_attributes (get_struct_attrs()) (elab_attributes env a) in
+          add_attributes (get_definition_attrs()) (elab_attributes env a) in
         let (id', env') =
           elab_struct_or_union only Struct loc id optmembers a' env in
         let ty =  TStruct(id', !attr) in
@@ -732,7 +736,7 @@ let rec elab_specifier ?(only = false) loc env specifier =
 
     | [Cabs.Tstruct_union(UNION, id, optmembers, a)] ->
         let a' =
-          add_attributes (get_struct_attrs()) (elab_attributes env a) in
+          add_attributes (get_definition_attrs()) (elab_attributes env a) in
         let (id', env') =
           elab_struct_or_union only Union loc id optmembers a' env in
         let ty =  TUnion(id', !attr) in
@@ -741,7 +745,7 @@ let rec elab_specifier ?(only = false) loc env specifier =
 
     | [Cabs.Tenum(id, optmembers, a)] ->
         let a' =
-          add_attributes (get_struct_attrs()) (elab_attributes env a) in
+          add_attributes (get_definition_attrs()) (elab_attributes env a) in
         let (id', env') =
           elab_enum only loc id optmembers a' env in
         let ty = TEnum (id', !attr) in