1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef MOJO_PUBLIC_C_SYSTEM_MACROS_H_
6#define MOJO_PUBLIC_C_SYSTEM_MACROS_H_
7
8#include <stddef.h>
9
10// Annotate a variable indicating it's okay if it's unused.
11// Use like:
12//   int x MOJO_ALLOW_UNUSED = ...;
13#if defined(__GNUC__)
14#define MOJO_ALLOW_UNUSED __attribute__((unused))
15#else
16#define MOJO_ALLOW_UNUSED
17#endif
18
19// Annotate a function indicating that the caller must examine the return value.
20// Use like:
21//   int foo() MOJO_WARN_UNUSED_RESULT;
22// Note that it can only be used on the prototype, and not the definition.
23#if defined(__GNUC__)
24#define MOJO_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
25#else
26#define MOJO_WARN_UNUSED_RESULT
27#endif
28
29// Assert things at compile time. (|msg| should be a valid identifier name.)
30// This macro is currently C++-only, but we want to use it in the C core.h.
31// Use like:
32//   MOJO_COMPILE_ASSERT(sizeof(Foo) == 12, Foo_has_invalid_size);
33#if __cplusplus >= 201103L
34#define MOJO_COMPILE_ASSERT(expr, msg) static_assert(expr, #msg)
35#elif defined(__cplusplus)
36namespace mojo { template <bool> struct CompileAssert {}; }
37#define MOJO_COMPILE_ASSERT(expr, msg) \
38    typedef ::mojo::CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1]
39#else
40#define MOJO_COMPILE_ASSERT(expr, msg)
41#endif
42
43// Like the C++11 |alignof| operator.
44#if __cplusplus >= 201103L
45#define MOJO_ALIGNOF(type) alignof(type)
46#elif defined(__GNUC__)
47#define MOJO_ALIGNOF(type) __alignof__(type)
48#elif defined(_MSC_VER)
49// The use of |sizeof| is to work around a bug in MSVC 2010 (see
50// http://goo.gl/isH0C; supposedly fixed since then).
51#define MOJO_ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
52#else
53#error "Please define MOJO_ALIGNOF() for your compiler."
54#endif
55
56// Specify the alignment of a |struct|, etc.
57// Use like:
58//   struct MOJO_ALIGNAS(8) Foo { ... };
59// Unlike the C++11 |alignas()|, |alignment| must be an integer. It may not be a
60// type, nor can it be an expression like |MOJO_ALIGNOF(type)| (due to the
61// non-C++11 MSVS version).
62#if __cplusplus >= 201103L
63#define MOJO_ALIGNAS(alignment) alignas(alignment)
64#elif defined(__GNUC__)
65#define MOJO_ALIGNAS(alignment) __attribute__((aligned(alignment)))
66#elif defined(_MSC_VER)
67#define MOJO_ALIGNAS(alignment) __declspec(align(alignment))
68#else
69#error "Please define MOJO_ALIGNAS() for your compiler."
70#endif
71
72#endif  // MOJO_PUBLIC_C_SYSTEM_MACROS_H_
73