[Ada] Fix wrong access check with access-to-unconstrained-array

The current implementation may create dangling references from a superset
of the alias set of the dummy pointer-to-array type when it exists.

gcc/ada/

	* gcc-interface/decl.cc (gnat_to_gnu_entity) <E_Array_Type>: Save
	and restore the alias set of the dummy pointer-to-array type.

diff --git a/gcc/ada/gcc-interface/decl.cc b/gcc/ada/gcc-interface/decl.cc
index 99277f0730617dcf17a522383e2590d781a168b4..2510ee8bc67d235b99b887acee2bd448f46d13d1 100644 (file)
--- a/gcc/ada/gcc-interface/decl.cc
+++ b/gcc/ada/gcc-interface/decl.cc
@@ -2102,15 +2102,15 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
        const bool convention_fortran_p
          = (Convention (gnat_entity) == Convention_Fortran);
        const int ndim = Number_Dimensions (gnat_entity);
-       tree gnu_template_type;
-       tree gnu_ptr_template;
-       tree gnu_template_reference, gnu_template_fields, gnu_fat_type;
+       tree gnu_fat_type, gnu_template_type, gnu_ptr_template;
+       tree gnu_template_reference, gnu_template_fields;
        tree *gnu_index_types = XALLOCAVEC (tree, ndim);
        tree *gnu_temp_fields = XALLOCAVEC (tree, ndim);
-       tree gnu_max_size = size_one_node, tem, obj;
+       tree gnu_max_size = size_one_node;
+       tree comp_type, tem, obj;
        Entity_Id gnat_index;
+       alias_set_type ptr_set = -1;
        int index;
-       tree comp_type;
 
        /* Create the type for the component now, as it simplifies breaking
           type reference loops.  */
@@ -2181,6 +2181,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
        if (COMPLETE_TYPE_P (gnu_fat_type))
          {
            tem = TYPE_FIELDS (gnu_fat_type);
+           if (TYPE_ALIAS_SET_KNOWN_P (TREE_TYPE (tem)))
+             ptr_set = TYPE_ALIAS_SET (TREE_TYPE (tem));
            TREE_TYPE (tem) = ptr_type_node;
            TREE_TYPE (DECL_CHAIN (tem)) = gnu_ptr_template;
            TYPE_DECL_SUPPRESS_DEBUG (TYPE_STUB_DECL (gnu_fat_type)) = 0;
@@ -2389,7 +2391,10 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
          tem = change_qualified_type (tem, TYPE_QUAL_VOLATILE);
 
        /* Adjust the type of the pointer-to-array field of the fat pointer
-          and record the aliasing relationships if necessary.  If this is
+          and preserve its existing alias set, if any.  Note that calling
+          again record_component_aliases on the fat pointer is not enough
+          because this may leave dangling references to the existing alias
+          set from types containing a fat pointer component.  If this is
           a packed type implemented specially, then use a ref-all pointer
           type since the implementation type may vary between constrained
           subtypes and unconstrained base type.  */
@@ -2398,8 +2403,8 @@ gnat_to_gnu_entity (Entity_Id gnat_entity, tree gnu_expr, bool definition)
            = build_pointer_type_for_mode (tem, ptr_mode, true);
        else
          TREE_TYPE (TYPE_FIELDS (gnu_fat_type)) = build_pointer_type (tem);
-       if (TYPE_ALIAS_SET_KNOWN_P (gnu_fat_type))
-         record_component_aliases (gnu_fat_type);
+       if (ptr_set != -1)
+         TYPE_ALIAS_SET (TREE_TYPE (TYPE_FIELDS (gnu_fat_type))) = ptr_set;
 
        /* If the maximum size doesn't overflow, use it.  */
        if (gnu_max_size