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       1                 :             : /* Template for deferring object creation until the object is needed.
       2                 :             :    Copyright (C) 2024-2025 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                 :             : class lazily_created
      31                 :             : {
      32                 :             :  public:
      33                 :             :   virtual ~lazily_created () {}
      34                 :             : 
      35                 :             :   const T &
      36                 :           4 :   get_or_create () const
      37                 :             :   {
      38                 :           4 :     if (!m_object)
      39                 :           4 :       m_object = create_object ();
      40                 :           4 :     gcc_assert (m_object);
      41                 :           4 :     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 */