[parsing] Allow attributes in declarator lists

Previously, the parser only allowed attributes at beginning of a declaration
(like for `const`, `static`, ...). However, gcc accepts to have attributes
in the rest of the declaration (after the first comma, like for a pointer or
 array declarator).

Fixes #616

src/kernel_internals/parsing/cparser.mly

@@ -1035,9 +1035,22 @@ declaration:                                /* ISO 6.7.*/
 
 init_declarator_list:                       /* ISO 6.7 */
     init_declarator                              { [$1] }
-|   init_declarator COMMA init_declarator_list   { $1 :: $3 }
+|   init_declarator COMMA init_declarator_attr_list   { $1 :: $3 }
 
 ;
+
+init_declarator_attr_list:
+  init_declarator_attr { [ $1 ] }
+| init_declarator_attr COMMA init_declarator_attr_list { $1 :: $3 }
+;
+
+init_declarator_attr:
+  attribute_nocv_list init_declarator {
+    let ((name, decl, attrs, loc), init) = $2 in
+    ((name, PARENTYPE ($1,decl,[]), attrs, loc), init)
+  }
+;
+
 init_declarator:                             /* ISO 6.7 */
     declarator                          { ($1, NO_INIT) }
 |   declarator EQ init_expression

tests/syntax/attributes-declarations-definitions.c

@@ -41,3 +41,7 @@ iptr h(volatile iptr ip2) {
 }
 
 iptr volatile h(const iptr ip3);
+
+void test(void) {
+  int a, __attribute__((unused)) b;
+}

tests/syntax/oracle/attributes-declarations-definitions.res.oracle

@@ -42,4 +42,11 @@ iptr h(iptr volatile ip3)
   return __retres;
 }
 
+void test(void)
+{
+  int a;
+  int b __attribute__((__unused__));
+  return;
+}
+