view libinterp/octave-value/ov-cell.h @ 29476:c74ff452e2bb stable

avoid memory leaks when returning handles to nested functions When a handle to a nested function is created with a std::shared_ptr object holding a reference to the stack frames associated with the parent function, we create a circular reference because the referenced stack frame contains the function handle object. To break the link, we'll scan the stack frame associated with the nested function handle and convert the shared_ptr links to be weak_ptr links instead, breaking the circular reference allowing the resources held by the closure frames to be released when all external references are cleared. Another possible solution to this problem is to create weak_ptr links initially and then convert them to shared_ptr links when the closure "escapes" the scope of the function. While that might be slightly more efficient (we would only have to look at assignments to global variables and the values that are actually returned from the function) the current design of global assignments does not make that easy because it is possible to ask for a reference to a global variable, so either all places where we grab references and then later perform assignments must be checked for assignments of handles to nested functions, or we must eliminate the interface that returns references to global variables and only allow assignments so that we would only have to perform the check in the assignment function(s). Perhaps this can be done in a future version, but for now, it works well enough to break the closure cycles in local variables when a function returns. * call-stack.cc (call_stack::pop): If popped stack frame is a closure context, then break closure cycles. * stack-frame.h, stack-frame.cc (stack_frame::m_is_closure_context): New member variable. (stack_frame::break_closure_cycles, user_fcn_stack_frame::break_closure_cycles): New functions. (stack_frame::mark_closure_context, stack_frame::is_closure_context): New functions. * ov-fcn-handle.h, ov-fcn-handle.cc (base_nested_fcn_handle): New base class for handles to nested functions. (nested_fcn_handle, weak_nested_fcn_handle): New classes to represent handles to nested functions. Currently, all handles to nested functions begin as nested_fcn_handle objects but are converted to weak_nested_fcn_handles when the functions where they are created return. (base_fcn_handle::is_nested (const std::shared_ptr<stack_frame>&) const, base_fcn_handle::make_weak_nested_handle, New virtual functions. (octave_fcn_handle::is_nested, octave_fcn_handle::is_weak_nested, octave_fcn_handle::make_weak_nested_handle): New functions. * ov-struct.h, ov-struct.cc (octave_scalar_map::break_closure_cycles, octave_map::break_closure_cycles): New functions. * ov.h, ov.cc (octave_value::break_closure_cycles): New function. * ov-base.h (octave_base_value::break_closure_cycles): New virtual function. * cdef-object.h (cdef_object::break_closure_cycles): New function. (cdef_object_rep::break_closure_cycles): New virtual function. * cdef-object.h, cdef-object.cc (cdef_object_scalar::break_closure_cycles): New function. * ov-cell.h, ov-cell.cc (octave_cell::break_closure_cycles): New function. * ov-class.h, ov-class.cc (octave_class::break_closure_cycles): New function. * ov-classdef.h (octave_classdef::break_closure_cycles): New function.
author John W. Eaton <jwe@octave.org>
date Fri, 05 Mar 2021 16:14:34 -0500
parents 0a5b15007766
children e88444be8468 d13d090cb03a
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////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 1999-2021 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
// <https://www.gnu.org/licenses/>.
//
////////////////////////////////////////////////////////////////////////

#if ! defined (octave_ov_cell_h)
#define octave_ov_cell_h 1

#include "octave-config.h"

#include <cstdlib>

#include <iosfwd>
#include <string>
#include <memory>

#include "mx-base.h"
#include "str-vec.h"

#include "Cell.h"
#include "error.h"
#include "ov-base-mat.h"
#include "ov-typeinfo.h"

class octave_value_list;

// Cells.

class
octave_cell : public octave_base_matrix<Cell>
{
public:

  octave_cell (void)
    : octave_base_matrix<Cell> (), cellstr_cache () { }

  octave_cell (const Cell& c)
    : octave_base_matrix<Cell> (c), cellstr_cache () { }

  octave_cell (const Array<std::string>& str)
    : octave_base_matrix<Cell> (Cell (str)),
      cellstr_cache (new Array<std::string> (str)) { }

  octave_cell (const octave_cell& c)
    : octave_base_matrix<Cell> (c), cellstr_cache () { }

  ~octave_cell (void) = default;

  octave_base_value * clone (void) const { return new octave_cell (*this); }
  octave_base_value * empty_clone (void) const { return new octave_cell (); }

  void break_closure_cycles (const std::shared_ptr<octave::stack_frame>& frame);

#if 0
  octave_base_value * try_narrowing_conversion (void);
#endif

  octave_value subsref (const std::string& type,
                        const std::list<octave_value_list>& idx)
  {
    octave_value_list tmp = subsref (type, idx, 1);
    return tmp.length () > 0 ? tmp(0) : octave_value ();
  }

  octave_value_list subsref (const std::string& type,
                             const std::list<octave_value_list>& idx,
                             int nargout);

  octave_value subsref (const std::string& type,
                        const std::list<octave_value_list>& idx,
                        bool auto_add);

  octave_value subsasgn (const std::string& type,
                         const std::list<octave_value_list>& idx,
                         const octave_value& rhs);

  // FIXME: should we import the functions from the base class and
  // overload them here, or should we use a different name so we don't
  // have to do this?  Without the using declaration or a name change,
  // the base class functions will be hidden.  That may be OK, but it
  // can also cause some confusion.
  using octave_base_value::assign;

  void assign (const octave_value_list& idx, const Cell& rhs);

  void assign (const octave_value_list& idx, const octave_value& rhs);

  void delete_elements (const octave_value_list& idx);

  size_t byte_size (void) const;

  octave_value sort (octave_idx_type dim = 0, sortmode mode = ASCENDING) const;

  octave_value sort (Array<octave_idx_type> &sidx, octave_idx_type dim = 0,
                     sortmode mode = ASCENDING) const;

  sortmode issorted (sortmode mode = UNSORTED) const;

  Array<octave_idx_type> sort_rows_idx (sortmode mode = ASCENDING) const;

  sortmode is_sorted_rows (sortmode mode = UNSORTED) const;

  bool is_matrix_type (void) const { return false; }

  bool isnumeric (void) const { return false; }

  bool is_defined (void) const { return true; }

  bool is_constant (void) const { return true; }

  bool iscell (void) const { return true; }

  builtin_type_t builtin_type (void) const { return btyp_cell; }

  bool iscellstr (void) const;

  bool is_true (void) const;

  Cell cell_value (void) const { return matrix; }

  octave_value_list list_value (void) const;

  octave_value convert_to_str_internal (bool pad, bool, char type) const
  { return octave_value (string_vector_value (pad), type); }

  string_vector string_vector_value (bool pad = false) const;

  Array<std::string> cellstr_value (void) const;

  Array<std::string> cellstr_value (const char *fmt, ...) const;

  bool print_as_scalar (void) const;

  void print (std::ostream& os, bool pr_as_read_syntax = false);

  void print_raw (std::ostream& os, bool pr_as_read_syntax = false) const;

  bool print_name_tag (std::ostream& os, const std::string& name) const;

  void short_disp (std::ostream& os) const;

  bool save_ascii (std::ostream& os);

  bool load_ascii (std::istream& is);

  bool save_binary (std::ostream& os, bool save_as_floats);

  bool load_binary (std::istream& is, bool swap,
                    octave::mach_info::float_format fmt);

  bool save_hdf5 (octave_hdf5_id loc_id, const char *name, bool save_as_floats);

  bool load_hdf5 (octave_hdf5_id loc_id, const char *name);

  octave_value map (unary_mapper_t umap) const;

  mxArray * as_mxArray (void) const;

  // Unsafe.  This function exists to support the MEX interface.
  // You should not use it anywhere else.
  void * mex_get_data (void) const;

private:

  void clear_cellstr_cache (void) const
  { cellstr_cache.reset (); }

  mutable std::unique_ptr<Array<std::string>> cellstr_cache;

  DECLARE_OV_TYPEID_FUNCTIONS_AND_DATA
};

#endif