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       1              : // Obstack-related utilities.
       2              : // Copyright (C) 2020-2026 Free Software Foundation, Inc.
       3              : //
       4              : // This file is part of GCC.
       5              : //
       6              : // GCC is free software; you can redistribute it and/or modify it under
       7              : // the terms of the GNU General Public License as published by the Free
       8              : // Software Foundation; either version 3, or (at your option) any later
       9              : // version.
      10              : //
      11              : // GCC is distributed in the hope that it will be useful, but WITHOUT ANY
      12              : // WARRANTY; without even the implied warranty of MERCHANTABILITY or
      13              : // FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
      14              : // for more details.
      15              : //
      16              : // You should have received a copy of the GNU General Public License
      17              : // along with GCC; see the file COPYING3.  If not see
      18              : // <http://www.gnu.org/licenses/>.
      19              : 
      20              : #ifndef GCC_OBSTACK_UTILS_H
      21              : #define GCC_OBSTACK_UTILS_H
      22              : 
      23              : // This RAII class automatically frees memory allocated on an obstack,
      24              : // unless told not to via keep ().  It automatically converts to an
      25              : // obstack, so it can (optionally) be used in place of the obstack
      26              : // to make the scoping clearer.  For example:
      27              : //
      28              : //     obstack_watermark watermark (ob);
      29              : //     auto *ptr1 = XOBNEW (watermark, struct1);
      30              : //     if (...)
      31              : //       // Frees ptr1.
      32              : //       return false;
      33              : //
      34              : //     auto *ptr2 = XOBNEW (watermark, struct2);
      35              : //     if (...)
      36              : //       // Frees ptr1 and ptr2.
      37              : //       return false;
      38              : //
      39              : //     // Retains ptr1 and ptr2.
      40              : //     watermark.keep ();
      41              : //
      42              : //     auto *ptr3 = XOBNEW (watermark, struct3);
      43              : //     if (...)
      44              : //       // Frees ptr3.
      45              : //       return false;
      46              : //
      47              : //     // Retains ptr3 (in addition to ptr1 and ptr2 above).
      48              : //     watermark.keep ();
      49              : //     return true;
      50              : //
      51              : // The move constructor makes it possible to transfer ownership to a caller:
      52              : //
      53              : //     obstack_watermark
      54              : //     foo ()
      55              : //     {
      56              : //       obstack_watermark watermark (ob);
      57              : //       ...
      58              : //       return watermark;
      59              : //     }
      60              : //
      61              : //     void
      62              : //     bar ()
      63              : //     {
      64              : //       // Inherit ownership of everything that foo allocated.
      65              : //       obstack_watermark watermark = foo ();
      66              : //       ...
      67              : //     }
      68              : class obstack_watermark
      69              : {
      70              : public:
      71    185793327 :   obstack_watermark (obstack *ob) : m_obstack (ob) { keep (); }
      72              :   constexpr obstack_watermark (obstack_watermark &&) = default;
      73    185793327 :   ~obstack_watermark () { obstack_free (m_obstack, m_start); }
      74              : 
      75    118112903 :   operator obstack *() const { return m_obstack; }
      76    249008417 :   void keep () { m_start = XOBNEWVAR (m_obstack, char, 0); }
      77              : 
      78              : private:
      79              :   DISABLE_COPY_AND_ASSIGN (obstack_watermark);
      80              : 
      81              : protected:
      82              :   obstack *m_obstack;
      83              :   char *m_start;
      84              : };
      85              : 
      86              : #endif