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 #ifdef __cplusplus
30 // Used to explicitly mark the return value of a function as unused. If you are
31 // really sure you don't want to do anything with the return value of a function
32 // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example:
33 //
34 // scoped_ptr<MyType> my_var = ...;
35 // if (TakeOwnership(my_var.get()) == SUCCESS)
36 // mojo_ignore_result(my_var.release());
37 //
38 template <typename T>
mojo_ignore_result(const T &)39 inline void mojo_ignore_result(const T&) {
40 }
41 #endif
42
43 // Assert things at compile time. (|msg| should be a valid identifier name.)
44 // This macro is currently C++-only, but we want to use it in the C core.h.
45 // Use like:
46 // MOJO_COMPILE_ASSERT(sizeof(Foo) == 12, Foo_has_invalid_size);
47 #if __cplusplus >= 201103L
48 #define MOJO_COMPILE_ASSERT(expr, msg) static_assert(expr, #msg)
49 #elif defined(__cplusplus)
50 namespace mojo {
51 template <bool>
52 struct CompileAssert {};
53 }
54 #define MOJO_COMPILE_ASSERT(expr, msg) \
55 typedef ::mojo::CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1]
56 #else
57 #define MOJO_COMPILE_ASSERT(expr, msg)
58 #endif
59
60 // Like the C++11 |alignof| operator.
61 #if __cplusplus >= 201103L
62 #define MOJO_ALIGNOF(type) alignof(type)
63 #elif defined(__GNUC__)
64 #define MOJO_ALIGNOF(type) __alignof__(type)
65 #elif defined(_MSC_VER)
66 // The use of |sizeof| is to work around a bug in MSVC 2010 (see
67 // http://goo.gl/isH0C; supposedly fixed since then).
68 #define MOJO_ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
69 #else
70 #error "Please define MOJO_ALIGNOF() for your compiler."
71 #endif
72
73 // Specify the alignment of a |struct|, etc.
74 // Use like:
75 // struct MOJO_ALIGNAS(8) Foo { ... };
76 // Unlike the C++11 |alignas()|, |alignment| must be an integer. It may not be a
77 // type, nor can it be an expression like |MOJO_ALIGNOF(type)| (due to the
78 // non-C++11 MSVS version).
79 #if __cplusplus >= 201103L
80 #define MOJO_ALIGNAS(alignment) alignas(alignment)
81 #elif defined(__GNUC__)
82 #define MOJO_ALIGNAS(alignment) __attribute__((aligned(alignment)))
83 #elif defined(_MSC_VER)
84 #define MOJO_ALIGNAS(alignment) __declspec(align(alignment))
85 #else
86 #error "Please define MOJO_ALIGNAS() for your compiler."
87 #endif
88
89 #endif // MOJO_PUBLIC_C_SYSTEM_MACROS_H_
90