Reject object-related and struct-related attributes on typedefs

This commit adds a check to reject type definitions such as
```
typedef __attribute((section "foo")) int fooint;
```
GCC and Clang also reject this as an error.

Without the check, the behavior is somewhat surprising:
```
fooint x;    // placed in section "foo"
fooint * x;  // placed in default section, attribute "foo" is ignored
```

Note that the following must be accepted:
```
typedef struct { ... } __attribute((packed)) t;
```
The "packed" attribute is correctly attached to the struct type and should not be checked.  This is achieved by using `attribute_of_type_no_expand` to get the attributes of the typedef-ed type, excluding the attributes carried by a struct/union or another typedef.

1 files changed, 1 insertions, 8 deletions

diff --git a/cparser/Checks.ml b/cparser/Checks.ml
index 62d85c1b..a30cde7d 100644
--- a/cparser/Checks.ml
+++ b/cparser/Checks.ml
@@ -18,19 +18,12 @@ open Diagnostics
 open Cutil
 open Env
 
-let attribute_string = function
-  | AConst -> "const"
-  | AVolatile -> "volatile"
-  | ARestrict -> "restrict"
-  | AAlignas n -> "_Alignas"
-  | Attr(name, _) ->  name
-
 let unknown_attrs loc attrs =
   let unknown attr =
     let attr_class = class_of_attribute attr in
     if attr_class = Attr_unknown then
       warning loc Unknown_attribute
-        "unknown attribute '%s' ignored" (attribute_string attr) in
+        "unknown attribute '%s' ignored" (name_of_attribute attr) in
   List.iter unknown attrs
 
 let unknown_attrs_typ env loc ty =