// ast_recursive.cpp,v 1.8 2002/02/04 16:48:58 parsons Exp

/*

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*/

// EXPLANATION: The CORBA spec says that the only legal use of recursive types is
// in a manifest sequence declared inside a struct or union whose base type is
// the struct or union.

// ALGORITHM FOR CHECK:
// Sequences push a NULL on the scope stack to mark where in the scope nesting
// they appear.

// - If the type is not a struct or union, return FALSE (legal use of type).
// - Otherwise check up the scope stack, looking for this base type. If we
//   find a NULL return FALSE (legal use of type, since it is inside some
//   sequence). If we find the type on the stack, return TRUE (illegal use
//   since it was not bracketed by a sequence). If we don't find the base
//   type nor a sequence, return FALSE (legal use, since we're not nested).

#include "idl.h"
#include "idl_extern.h"

ACE_RCSID(ast, ast_recursive, "ast_recursive.cpp,v 1.8 2002/02/04 16:48:58 parsons Exp")

idl_bool
AST_illegal_recursive_type (AST_Decl *t)
{
  if (t == 0)
    {
      return I_FALSE;
    }

  // We only care about structs and unions.
  if (t->node_type () != AST_Decl::NT_struct
      && t->node_type () != AST_Decl::NT_union)
    {
      return I_FALSE;	// NOT ILLEGAL.
    }

  idl_bool check_for_struct = I_FALSE;
	idl_bool check_for_union = I_FALSE;
  AST_Structure	*st1 = 0;
  AST_Union	*un1 = 0;

  // Narrow the type appropriately so comparison will work.
  if (t->node_type () == AST_Decl::NT_struct)
    {
      check_for_struct = I_TRUE;
      st1 = AST_Structure::narrow_from_decl (t);

      if (st1 == 0)
        {
          return I_FALSE;	// NOT ILLEGAL.
        }
    }
  else if (t->node_type () == AST_Decl::NT_union)
    {
      check_for_union = I_TRUE;
      un1 = AST_Union::narrow_from_decl (t);

      if (un1 == 0)
        {
          return I_FALSE;	// NOT ILLEGAL.
        }
    }

  UTL_Scope	*s = 0;
  AST_Structure *st2 = 0;
  AST_Union *un2 = 0;

  // OK, iterate up the stack.
  for (UTL_ScopeStackActiveIterator i (idl_global->scopes ());
       !i.is_done ();
       i.next ())
    {
      s = i.item ();

      // If we hit a NULL we're done since it means that we're nested inside
      // a sequence, where recursive types may be used.
      if (s == 0)
        {
          return I_FALSE;	// NOT ILLEGAL.
        }

      // OK, must check this scope.
      if (s->scope_node_type () == AST_Decl::NT_struct
          && check_for_struct == I_TRUE)
        {
          st2 = AST_Structure::narrow_from_scope (s);

          if (st2 != 0 && st2 == st1)
            {
              return I_TRUE;	// ILLEGAL RECURSIVE TYPE USE.
            }
        }
      else if (s->scope_node_type () == AST_Decl::NT_union
               && check_for_union == I_TRUE)
        {
          un2 = AST_Union::narrow_from_scope (s);

          if (un2 != 0 && un2 == un1)
            {
	            return I_TRUE;	// ILLEGAL RECURSIVE TYPE USE.
            }
        }
    }

  // No more scopes to check. This type was used legally.
  return I_FALSE;		// NOT ILLEGAL.
}

