StaticConstructors.h   [plain text]

 * Copyright (C) 2006 Apple Inc.
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Library General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * Library General Public License for more details.
 * You should have received a copy of the GNU Library General Public License
 * along with this library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301, USA.

#ifndef StaticConstructors_h
#define StaticConstructors_h

// We need to avoid having static constructors. We achieve this
// with two separate methods for GCC and MSVC. Both methods prevent the static
// initializers from being registered and called on program startup. On GCC, we
// declare the global objects with a different type that can be POD default
// initialized by the linker/loader. On MSVC we use a special compiler feature
// to have the CRT ignore our static initializers. The constructors will never
// be called and the objects will be left uninitialized.
// With both of these approaches, we must define and explicitly call an init
// routine that uses placement new to create the objects and overwrite the
// uninitialized placeholders.
// This is not completely portable, but is what we have for now without
// changing how a lot of code accesses these global objects.

// - Assume that all includes of this header want ALL of their static
//   initializers ignored. This is currently the case. This means that if
//   a .cc includes this header (or it somehow gets included), all static
//   initializers after the include will not be executed.
// - We do this with a pragma, so that all of the static initializer pointers
//   go into our own section, and the CRT won't call them. Eventually it would
//   be nice if the section was discarded, because we don't want the pointers.
//   See:
#pragma warning(disable:4075)
#pragma init_seg(".unwantedstaticinits")

    // Define an global in the normal way.
#define DEFINE_GLOBAL(type, name, ...) \
    const type name;

// Define an correctly-sized array of pointers to avoid static initialization.
// Use an array of pointers instead of an array of char in case there is some alignment issue.
#define DEFINE_GLOBAL(type, name, ...) \
    void * name[(sizeof(type) + sizeof(void *) - 1) / sizeof(void *)];

#endif // StaticConstructors_h