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       1              : /* Template for deferring object creation until the object is needed.
       2              :    Copyright (C) 2024-2026 Free Software Foundation, Inc.
       3              :    Contributed by David Malcolm <dmalcolm@redhat.com>
       4              : 
       5              : This file is part of GCC.
       6              : 
       7              : GCC is free software; you can redistribute it and/or modify it under
       8              : the terms of the GNU General Public License as published by the Free
       9              : Software Foundation; either version 3, or (at your option) any later
      10              : version.
      11              : 
      12              : GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      13              : WARRANTY; without even the implied warranty of MERCHANTABILITY or
      14              : FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      15              : for more details.
      16              : 
      17              : You should have received a copy of the GNU General Public License
      18              : along with GCC; see the file COPYING3.  If not see
      19              : <http://www.gnu.org/licenses/>.  */
      20              : 
      21              : #ifndef GCC_LAZILY_CREATED_H
      22              : #define GCC_LAZILY_CREATED_H
      23              : 
      24              : /* A template for deferring object creation for a type T until the object
      25              :    is needed, to avoid potentially expensive creation of T unless it's
      26              :    actually needed (e.g. for directed graphs associated with a diagnostic,
      27              :    which are ignored by the default "text" sink).  */
      28              : 
      29              : template <typename T>
      30           90 : class lazily_created
      31              : {
      32              :  public:
      33           90 :   virtual ~lazily_created () {}
      34              : 
      35              :   const T &
      36           94 :   get_or_create () const
      37              :   {
      38           94 :     if (!m_object)
      39           94 :       m_object = create_object ();
      40           94 :     gcc_assert (m_object);
      41           94 :     return *m_object;
      42              :   }
      43              : 
      44              : private:
      45              :   virtual std::unique_ptr<T>
      46              :   create_object () const = 0;
      47              : 
      48              :   mutable std::unique_ptr<T> m_object;
      49              : };
      50              : 
      51              : #endif /* ! GCC_LAZILY_CREATED_H */