third_party/WebKit/Source/wtf/StaticConstructors.h

   1 /*
   2  * Copyright (C) 2006 Apple Computer, Inc.
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Library General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Library General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Library General Public License
  15  * along with this library; see the file COPYING.LIB.  If not, write to
  16  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA 02110-1301, USA.
  18  *
  19  */
  20
  21 #ifndef StaticConstructors_h
  22 #define StaticConstructors_h
  23
  24 // We need to avoid having static constructors. This is accomplished by defining
  25 // a static array of the appropriate size and alignment, and defining a const
  26 // reference that points to the buffer. During initialization, the object will
  27 // be constructed with placement new into the buffer. This works with MSVC, GCC,
  28 // and Clang without producing dynamic initialization code even at -O0. The only
  29 // downside is that all external translation units will have to emit one more
  30 // load, while a real global could be referenced directly by absolute or
  31 // relative addressing.
  32
  33 // Use an array of pointers instead of an array of char in case there is some alignment issue.
  34 #define DEFINE_GLOBAL(type, name, ...) \
  35     void* name##Storage[(sizeof(type) + sizeof(void *) - 1) / sizeof(void *)]; \
  36     const type& name = *reinterpret_cast<type*>(&name##Storage);
  37
  38 #endif // StaticConstructors_h