1/*
2 * Copyright (C) 2006 Apple 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. We achieve this
25// with two separate methods for GCC and MSVC. Both methods prevent the static
26// initializers from being registered and called on program startup. On GCC, we
27// declare the global objects with a different type that can be POD default
28// initialized by the linker/loader. On MSVC we use a special compiler feature
29// to have the CRT ignore our static initializers. The constructors will never
30// be called and the objects will be left uninitialized.
31//
32// With both of these approaches, we must define and explicitly call an init
33// routine that uses placement new to create the objects and overwrite the
34// uninitialized placeholders.
35//
36// This is not completely portable, but is what we have for now without
37// changing how a lot of code accesses these global objects.
38
39#ifdef SKIP_STATIC_CONSTRUCTORS_ON_MSVC
40// - Assume that all includes of this header want ALL of their static
41//   initializers ignored. This is currently the case. This means that if
42//   a .cc includes this header (or it somehow gets included), all static
43//   initializers after the include will not be executed.
44// - We do this with a pragma, so that all of the static initializer pointers
45//   go into our own section, and the CRT won't call them. Eventually it would
46//   be nice if the section was discarded, because we don't want the pointers.
47//   See: http://msdn.microsoft.com/en-us/library/7977wcck(VS.80).aspx
48#pragma warning(disable:4075)
49#pragma init_seg(".unwantedstaticinits")
50#endif
51
52#ifndef SKIP_STATIC_CONSTRUCTORS_ON_GCC
53    // Define an global in the normal way.
54#define DEFINE_GLOBAL(type, name, ...) \
55    const type name;
56
57#else
58// Define an correctly-sized array of pointers to avoid static initialization.
59// Use an array of pointers instead of an array of char in case there is some alignment issue.
60#define DEFINE_GLOBAL(type, name, ...) \
61    void * name[(sizeof(type) + sizeof(void *) - 1) / sizeof(void *)];
62#endif
63
64#endif // StaticConstructors_h
65