87 lines
2.4 KiB
C++
87 lines
2.4 KiB
C++
// Obstack-related utilities.
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// Copyright (C) 2020-2023 Free Software Foundation, Inc.
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//
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// This file is part of GCC.
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//
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// GCC is free software; you can redistribute it and/or modify it under
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// the terms of the GNU General Public License as published by the Free
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// Software Foundation; either version 3, or (at your option) any later
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// version.
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//
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// GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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// WARRANTY; without even the implied warranty of MERCHANTABILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with GCC; see the file COPYING3. If not see
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// <http://www.gnu.org/licenses/>.
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#ifndef GCC_OBSTACK_UTILS_H
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#define GCC_OBSTACK_UTILS_H
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// This RAII class automatically frees memory allocated on an obstack,
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// unless told not to via keep (). It automatically converts to an
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// obstack, so it can (optionally) be used in place of the obstack
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// to make the scoping clearer. For example:
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//
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// obstack_watermark watermark (ob);
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// auto *ptr1 = XOBNEW (watermark, struct1);
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// if (...)
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// // Frees ptr1.
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// return false;
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//
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// auto *ptr2 = XOBNEW (watermark, struct2);
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// if (...)
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// // Frees ptr1 and ptr2.
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// return false;
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//
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// // Retains ptr1 and ptr2.
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// watermark.keep ();
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//
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// auto *ptr3 = XOBNEW (watermark, struct3);
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// if (...)
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// // Frees ptr3.
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// return false;
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//
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// // Retains ptr3 (in addition to ptr1 and ptr2 above).
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// watermark.keep ();
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// return true;
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//
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// The move constructor makes it possible to transfer ownership to a caller:
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//
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// obstack_watermark
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// foo ()
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// {
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// obstack_watermark watermark (ob);
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// ...
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// return watermark;
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// }
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//
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// void
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// bar ()
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// {
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// // Inherit ownership of everything that foo allocated.
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// obstack_watermark watermark = foo ();
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// ...
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// }
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class obstack_watermark
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{
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public:
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obstack_watermark (obstack *ob) : m_obstack (ob) { keep (); }
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constexpr obstack_watermark (obstack_watermark &&) = default;
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~obstack_watermark () { obstack_free (m_obstack, m_start); }
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operator obstack *() const { return m_obstack; }
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void keep () { m_start = XOBNEWVAR (m_obstack, char, 0); }
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private:
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DISABLE_COPY_AND_ASSIGN (obstack_watermark);
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protected:
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obstack *m_obstack;
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char *m_start;
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};
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#endif
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