refactor octave_function call method This change is a step toward keeping stack frames for closures (handles to nested functions) separate from the functions themselves. * call-stack.h, call-stack.cc (call_stack::curr_fcn_unwind_protect_frame: No longer const. Update all uses. (call_stack::push): Dliminate unwind protect frame argument. Change all uses. * stack-frame.h, stack-frame.cc (script_stack_frame, user_fcn_stack_frame): Create uniwnd_protect_frame only if needed. * ov-builtin.h, ov-builtin.cc (octave_builtin::execute): New function that executes function without pushing stack frame. (octave_builtin::call): Delete. * ov-class.h, ov-class.cc (octave_inline_fcn::execute): New function. (octave_inline_fcn::call): Call execute. * ov-classdef.h, ov-classdef.cc (octave_classdef_meta::execute): New function. (octave_classdef_meta::call): Call execute. (octave_classdef_superclass_ref::execute): New function. (octave_classdef_superclass_ref::call): Call execute. * ov-fcn-handle.cc (octave_fcn_handle::call): When calling a function that has closure_frames, push stack frame here instead of inside octave_user_function object. * ov-fcn.h (octave_function::execute): New pure virtual function. * ov-fcn.h, ov-fcn.cc (octave_function::call): Define only one variant, without closure frames as an argument. Default version simply pushes stack frame and calls execute. * ov-mex-fcn.h, ov-mex-fcn.cc (octave_mex_function::execute): Rename from call. Don't push stack frame here. * ov-usr-fcn.h, ov-usr-fcn.cc (octave_user_script::call, octave_user_function::call): Push stack frame and call execute. (octave_user_script::execute, octave_user_function::execute): New function. * pt-eval.h, pt-eval.cc (tree_evaluator::push_stack_frame): Eliminate unwind protect frame argument. Change all uses. (tree_evaluator::execute_user_script): Update. (tree_evaluator::execute_user_function): Update. Don't push stack frame here.

////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1996-2020 The Octave Project Developers
//
// See the file COPYRIGHT.md in the top-level directory of this
// distribution or <https://octave.org/copyright/>.
//
// This file is part of Octave.
//
// Octave is free software: you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Octave is distributed in the hope that it will be useful, but
// WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Octave; see the file COPYING.  If not, see
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////////////////////////////////////////////////////////////////////////

#if defined (HAVE_CONFIG_H)
#  include "config.h"
#endif

#include "unwind-prot.h"

#include "error.h"
#include "ovl.h"
#include "ov-fcn.h"
#include "pt-eval.h"

octave_base_value *
octave_function::clone (void) const
{
  panic_impossible ();
}

octave_base_value *
octave_function::empty_clone (void) const
{
  panic_impossible ();
}

octave_value_list
octave_function::call (octave::tree_evaluator& tw, int nargout,
                       const octave_value_list& args)
{
  tw.push_stack_frame (this);

  octave::unwind_action act ([&tw] () { tw.pop_stack_frame (); });

  return execute (tw, nargout, args);
}