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// Obstack-related utilities.
// Copyright (C) 2020-2022 Free Software Foundation, Inc.
//
// This file is part of GCC.
//
// GCC 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, or (at your option) any later
// version.
//
// GCC 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 GCC; see the file COPYING3. If not see
// <http://www.gnu.org/licenses/>.
#ifndef GCC_OBSTACK_UTILS_H
#define GCC_OBSTACK_UTILS_H
// This RAII class automatically frees memory allocated on an obstack,
// unless told not to via keep (). It automatically converts to an
// obstack, so it can (optionally) be used in place of the obstack
// to make the scoping clearer. For example:
//
// obstack_watermark watermark (ob);
// auto *ptr1 = XOBNEW (watermark, struct1);
// if (...)
// // Frees ptr1.
// return false;
//
// auto *ptr2 = XOBNEW (watermark, struct2);
// if (...)
// // Frees ptr1 and ptr2.
// return false;
//
// // Retains ptr1 and ptr2.
// watermark.keep ();
//
// auto *ptr3 = XOBNEW (watermark, struct3);
// if (...)
// // Frees ptr3.
// return false;
//
// // Retains ptr3 (in addition to ptr1 and ptr2 above).
// watermark.keep ();
// return true;
//
// The move constructor makes it possible to transfer ownership to a caller:
//
// obstack_watermark
// foo ()
// {
// obstack_watermark watermark (ob);
// ...
// return watermark;
// }
//
// void
// bar ()
// {
// // Inherit ownership of everything that foo allocated.
// obstack_watermark watermark = foo ();
// ...
// }
class obstack_watermark
{
public:
obstack_watermark (obstack *ob) : m_obstack (ob) { keep (); }
constexpr obstack_watermark (obstack_watermark &&) = default;
~obstack_watermark () { obstack_free (m_obstack, m_start); }
operator obstack *() const { return m_obstack; }
void keep () { m_start = XOBNEWVAR (m_obstack, char, 0); }
private:
DISABLE_COPY_AND_ASSIGN (obstack_watermark);
protected:
obstack *m_obstack;
char *m_start;
};
#endif
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