1// Copyright (c) 2012 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 BASE_COMPILER_SPECIFIC_H_
6#define BASE_COMPILER_SPECIFIC_H_
7
8#include "build/build_config.h"
9
10#if defined(COMPILER_MSVC)
11
12// Macros for suppressing and disabling warnings on MSVC.
13//
14// Warning numbers are enumerated at:
15// http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
16//
17// The warning pragma:
18// http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
19//
20// Using __pragma instead of #pragma inside macros:
21// http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
22
23// MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
24// for the next line of the source file.
25#define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress:n))
26
27// MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
28// The warning remains disabled until popped by MSVC_POP_WARNING.
29#define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
30                                     __pragma(warning(disable:n))
31
32// MSVC_PUSH_WARNING_LEVEL pushes |n| as the global warning level.  The level
33// remains in effect until popped by MSVC_POP_WARNING().  Use 0 to disable all
34// warnings.
35#define MSVC_PUSH_WARNING_LEVEL(n) __pragma(warning(push, n))
36
37// Pop effects of innermost MSVC_PUSH_* macro.
38#define MSVC_POP_WARNING() __pragma(warning(pop))
39
40#define MSVC_DISABLE_OPTIMIZE() __pragma(optimize("", off))
41#define MSVC_ENABLE_OPTIMIZE() __pragma(optimize("", on))
42
43// Allows exporting a class that inherits from a non-exported base class.
44// This uses suppress instead of push/pop because the delimiter after the
45// declaration (either "," or "{") has to be placed before the pop macro.
46//
47// Example usage:
48// class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
49//
50// MSVC Compiler warning C4275:
51// non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
52// Note that this is intended to be used only when no access to the base class'
53// static data is done through derived classes or inline methods. For more info,
54// see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
55#define NON_EXPORTED_BASE(code) MSVC_SUPPRESS_WARNING(4275) \
56                                code
57
58#else  // Not MSVC
59
60#define MSVC_SUPPRESS_WARNING(n)
61#define MSVC_PUSH_DISABLE_WARNING(n)
62#define MSVC_PUSH_WARNING_LEVEL(n)
63#define MSVC_POP_WARNING()
64#define MSVC_DISABLE_OPTIMIZE()
65#define MSVC_ENABLE_OPTIMIZE()
66#define NON_EXPORTED_BASE(code) code
67
68#endif  // COMPILER_MSVC
69
70
71// The C++ standard requires that static const members have an out-of-class
72// definition (in a single compilation unit), but MSVC chokes on this (when
73// language extensions, which are required, are enabled). (You're only likely to
74// notice the need for a definition if you take the address of the member or,
75// more commonly, pass it to a function that takes it as a reference argument --
76// probably an STL function.) This macro makes MSVC do the right thing. See
77// http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more
78// information. Use like:
79//
80// In .h file:
81//   struct Foo {
82//     static const int kBar = 5;
83//   };
84//
85// In .cc file:
86//   STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar;
87#if defined(COMPILER_MSVC)
88#define STATIC_CONST_MEMBER_DEFINITION __declspec(selectany)
89#else
90#define STATIC_CONST_MEMBER_DEFINITION
91#endif
92
93// Annotate a variable indicating it's ok if the variable is not used.
94// (Typically used to silence a compiler warning when the assignment
95// is important for some other reason.)
96// Use like:
97//   int x ALLOW_UNUSED = ...;
98#if defined(COMPILER_GCC)
99#define ALLOW_UNUSED __attribute__((unused))
100#else
101#define ALLOW_UNUSED
102#endif
103
104// Annotate a function indicating it should not be inlined.
105// Use like:
106//   NOINLINE void DoStuff() { ... }
107#if defined(COMPILER_GCC)
108#define NOINLINE __attribute__((noinline))
109#elif defined(COMPILER_MSVC)
110#define NOINLINE __declspec(noinline)
111#else
112#define NOINLINE
113#endif
114
115// Specify memory alignment for structs, classes, etc.
116// Use like:
117//   class ALIGNAS(16) MyClass { ... }
118//   ALIGNAS(16) int array[4];
119#if defined(COMPILER_MSVC)
120#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
121#elif defined(COMPILER_GCC)
122#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
123#endif
124
125// Return the byte alignment of the given type (available at compile time).  Use
126// sizeof(type) prior to checking __alignof to workaround Visual C++ bug:
127// http://goo.gl/isH0C
128// Use like:
129//   ALIGNOF(int32)  // this would be 4
130#if defined(COMPILER_MSVC)
131#define ALIGNOF(type) (sizeof(type) - sizeof(type) + __alignof(type))
132#elif defined(COMPILER_GCC)
133#define ALIGNOF(type) __alignof__(type)
134#endif
135
136// Annotate a virtual method indicating it must be overriding a virtual
137// method in the parent class.
138// Use like:
139//   virtual void foo() OVERRIDE;
140#define OVERRIDE override
141
142// Annotate a virtual method indicating that subclasses must not override it,
143// or annotate a class to indicate that it cannot be subclassed.
144// Use like:
145//   virtual void foo() FINAL;
146//   class B FINAL : public A {};
147#define FINAL final
148
149// Annotate a function indicating the caller must examine the return value.
150// Use like:
151//   int foo() WARN_UNUSED_RESULT;
152// To explicitly ignore a result, see |ignore_result()| in <base/basictypes.h>.
153#if defined(COMPILER_GCC)
154#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
155#else
156#define WARN_UNUSED_RESULT
157#endif
158
159// Tell the compiler a function is using a printf-style format string.
160// |format_param| is the one-based index of the format string parameter;
161// |dots_param| is the one-based index of the "..." parameter.
162// For v*printf functions (which take a va_list), pass 0 for dots_param.
163// (This is undocumented but matches what the system C headers do.)
164#if defined(COMPILER_GCC)
165#define PRINTF_FORMAT(format_param, dots_param) \
166    __attribute__((format(printf, format_param, dots_param)))
167#else
168#define PRINTF_FORMAT(format_param, dots_param)
169#endif
170
171// WPRINTF_FORMAT is the same, but for wide format strings.
172// This doesn't appear to yet be implemented in any compiler.
173// See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
174#define WPRINTF_FORMAT(format_param, dots_param)
175// If available, it would look like:
176//   __attribute__((format(wprintf, format_param, dots_param)))
177
178// MemorySanitizer annotations.
179#if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
180#include <sanitizer/msan_interface.h>
181
182// Mark a memory region fully initialized.
183// Use this to annotate code that deliberately reads uninitialized data, for
184// example a GC scavenging root set pointers from the stack.
185#define MSAN_UNPOISON(p, s)  __msan_unpoison(p, s)
186#else  // MEMORY_SANITIZER
187#define MSAN_UNPOISON(p, s)
188#endif  // MEMORY_SANITIZER
189
190// Macro useful for writing cross-platform function pointers.
191#if !defined(CDECL)
192#if defined(OS_WIN)
193#define CDECL __cdecl
194#else  // defined(OS_WIN)
195#define CDECL
196#endif  // defined(OS_WIN)
197#endif  // !defined(CDECL)
198
199// Macro for hinting that an expression is likely to be false.
200#if !defined(UNLIKELY)
201#if defined(COMPILER_GCC)
202#define UNLIKELY(x) __builtin_expect(!!(x), 0)
203#else
204#define UNLIKELY(x) (x)
205#endif  // defined(COMPILER_GCC)
206#endif  // !defined(UNLIKELY)
207
208#endif  // BASE_COMPILER_SPECIFIC_H_
209