[Bug c/97413] [11 Regression] gcc-11 fails to typecheck VLA declarations on emacs-27.1: error: wrong number of arguments specified for 'access' attribute

["msebor at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97413

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |msebor at gcc dot gnu.org

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The explicit attribute access takes to two or three arguments.  Array and VLA
arguments are represented as an implicit access attributes, with the VLA bounds
chained on to the end of the attribute.  The untested patch below fixes the
problem by wrapping the arbitrarily long chain in a list with just a single
value.

diff --git a/gcc/attribs.c b/gcc/attribs.c
index 94b9e02699f..325799f0442 100644
--- a/gcc/attribs.c
+++ b/gcc/attribs.c
@@ -2049,6 +2049,8 @@ init_attr_rdwr_indices (rdwr_map *rwm, tree attrs)

       /* The (optional) list of VLA bounds.  */
       tree vblist = TREE_CHAIN (mode);
+      if (vblist)
+       vblist = TREE_VALUE (vblist);

       mode = TREE_VALUE (mode);
       if (TREE_CODE (mode) != STRING_CST)
diff --git a/gcc/c-family/c-attribs.c b/gcc/c-family/c-attribs.c
index c779d13f023..8283e959c89 100644
--- a/gcc/c-family/c-attribs.c
+++ b/gcc/c-family/c-attribs.c
@@ -4547,10 +4547,11 @@ handle_access_attribute (tree node[3], tree name, tree
args,
    result in the following attribute access:

      value: "+^2[*],$0$1^3[*],$1$1"
-     chain: <0, x> <1, y>
+     list:  < <0, x> <1, y> >

-   where each <node> on the chain corresponds to one VLA bound for each
-   of the two parameters.  */
+   where the list has a single value which itself is is a list each
+   of whose <node>s corresponds to one VLA bound for each of the two
+   parameters.  */

 tree
 build_attr_access_from_parms (tree parms, bool skip_voidptr)
@@ -4654,13 +4655,17 @@ build_attr_access_from_parms (tree parms, bool
skip_voidptr)
   if (!spec.length ())
     return NULL_TREE;

+  /* Attribute access takes a two or three arguments.  Wrap VBLIST in
+     another list in case it has more nodes than would otherwise fit.  */
+    vblist = build_tree_list (NULL_TREE, vblist);
+
   /* Build a single attribute access with the string describing all
      array arguments and an optional list of any non-parameter VLA
      bounds in order.  */
   tree str = build_string (spec.length (), spec.c_str ());
   tree attrargs = tree_cons (NULL_TREE, str, vblist);
   tree name = get_identifier ("access");
-  return tree_cons (name, attrargs, NULL_TREE);
+  return build_tree_list (name, attrargs);
 }

 /* Handle a "nothrow" attribute; arguments as in