compiler_specific.h revision cce46a0c214b37e8da48c522c83037e8ffa4f9fd 
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// For _Printf_format_string_.
13#include <sal.h>
14
15// Macros for suppressing and disabling warnings on MSVC.
16//
17// Warning numbers are enumerated at:
18// http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
19//
20// The warning pragma:
21// http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
22//
23// Using __pragma instead of #pragma inside macros:
24// http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
25
26// MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
27// for the next line of the source file.
28#define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress:n))
29
30// MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
31// The warning remains disabled until popped by MSVC_POP_WARNING.
32#define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
33                                     __pragma(warning(disable:n))
34
35// MSVC_PUSH_WARNING_LEVEL pushes |n| as the global warning level.  The level
36// remains in effect until popped by MSVC_POP_WARNING().  Use 0 to disable all
37// warnings.
38#define MSVC_PUSH_WARNING_LEVEL(n) __pragma(warning(push, n))
39
40// Pop effects of innermost MSVC_PUSH_* macro.
41#define MSVC_POP_WARNING() __pragma(warning(pop))
42
43#define MSVC_DISABLE_OPTIMIZE() __pragma(optimize("", off))
44#define MSVC_ENABLE_OPTIMIZE() __pragma(optimize("", on))
45
46// Allows exporting a class that inherits from a non-exported base class.
47// This uses suppress instead of push/pop because the delimiter after the
48// declaration (either "," or "{") has to be placed before the pop macro.
49//
50// Example usage:
51// class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
52//
53// MSVC Compiler warning C4275:
54// non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
55// Note that this is intended to be used only when no access to the base class'
56// static data is done through derived classes or inline methods. For more info,
57// see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
58#define NON_EXPORTED_BASE(code) MSVC_SUPPRESS_WARNING(4275) \
59                                code
60
61#else  // Not MSVC
62
63#define _Printf_format_string_
64#define MSVC_SUPPRESS_WARNING(n)
65#define MSVC_PUSH_DISABLE_WARNING(n)
66#define MSVC_PUSH_WARNING_LEVEL(n)
67#define MSVC_POP_WARNING()
68#define MSVC_DISABLE_OPTIMIZE()
69#define MSVC_ENABLE_OPTIMIZE()
70#define NON_EXPORTED_BASE(code) code
71
72#endif  // COMPILER_MSVC
73
74
75// Annotate a variable indicating it's ok if the variable is not used.
76// (Typically used to silence a compiler warning when the assignment
77// is important for some other reason.)
78// Use like:
79//   int x = ...;
80//   ALLOW_UNUSED_LOCAL(x);
81#define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
82
83// Annotate a typedef or function indicating it's ok if it's not used.
84// Use like:
85//   typedef Foo Bar ALLOW_UNUSED_TYPE;
86#if defined(COMPILER_GCC) || defined(__clang__)
87#define ALLOW_UNUSED_TYPE __attribute__((unused))
88#else
89#define ALLOW_UNUSED_TYPE
90#endif
91
92// Annotate a function indicating it should not be inlined.
93// Use like:
94//   NOINLINE void DoStuff() { ... }
95#if defined(COMPILER_GCC)
96#define NOINLINE __attribute__((noinline))
97#elif defined(COMPILER_MSVC)
98#define NOINLINE __declspec(noinline)
99#else
100#define NOINLINE
101#endif
102
103// Specify memory alignment for structs, classes, etc.
104// Use like:
105//   class ALIGNAS(16) MyClass { ... }
106//   ALIGNAS(16) int array[4];
107#if defined(COMPILER_MSVC)
108#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
109#elif defined(COMPILER_GCC)
110#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
111#endif
112
113// Return the byte alignment of the given type (available at compile time).
114// Use like:
115//   ALIGNOF(int32_t)  // this would be 4
116#if defined(COMPILER_MSVC)
117#define ALIGNOF(type) __alignof(type)
118#elif defined(COMPILER_GCC)
119#define ALIGNOF(type) __alignof__(type)
120#endif
121
122// Annotate a function indicating the caller must examine the return value.
123// Use like:
124//   int foo() WARN_UNUSED_RESULT;
125// To explicitly ignore a result, see |ignore_result()| in base/macros.h.
126#undef WARN_UNUSED_RESULT
127#if defined(COMPILER_GCC) || defined(__clang__)
128#define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
129#else
130#define WARN_UNUSED_RESULT
131#endif
132
133// Tell the compiler a function is using a printf-style format string.
134// |format_param| is the one-based index of the format string parameter;
135// |dots_param| is the one-based index of the "..." parameter.
136// For v*printf functions (which take a va_list), pass 0 for dots_param.
137// (This is undocumented but matches what the system C headers do.)
138#if defined(COMPILER_GCC)
139#define PRINTF_FORMAT(format_param, dots_param) \
140    __attribute__((format(printf, format_param, dots_param)))
141#else
142#define PRINTF_FORMAT(format_param, dots_param)
143#endif
144
145// WPRINTF_FORMAT is the same, but for wide format strings.
146// This doesn't appear to yet be implemented in any compiler.
147// See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
148#define WPRINTF_FORMAT(format_param, dots_param)
149// If available, it would look like:
150//   __attribute__((format(wprintf, format_param, dots_param)))
151
152// MemorySanitizer annotations.
153#if defined(MEMORY_SANITIZER) && !defined(OS_NACL)
154#include <sanitizer/msan_interface.h>
155
156// Mark a memory region fully initialized.
157// Use this to annotate code that deliberately reads uninitialized data, for
158// example a GC scavenging root set pointers from the stack.
159#define MSAN_UNPOISON(p, size)  __msan_unpoison(p, size)
160
161// Check a memory region for initializedness, as if it was being used here.
162// If any bits are uninitialized, crash with an MSan report.
163// Use this to sanitize data which MSan won't be able to track, e.g. before
164// passing data to another process via shared memory.
165#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
166    __msan_check_mem_is_initialized(p, size)
167#else  // MEMORY_SANITIZER
168#define MSAN_UNPOISON(p, size)
169#define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
170#endif  // MEMORY_SANITIZER
171
172// Macro useful for writing cross-platform function pointers.
173#if !defined(CDECL)
174#if defined(OS_WIN)
175#define CDECL __cdecl
176#else  // defined(OS_WIN)
177#define CDECL
178#endif  // defined(OS_WIN)
179#endif  // !defined(CDECL)
180
181// Macro for hinting that an expression is likely to be false.
182#if !defined(UNLIKELY)
183#if defined(COMPILER_GCC)
184#define UNLIKELY(x) __builtin_expect(!!(x), 0)
185#else
186#define UNLIKELY(x) (x)
187#endif  // defined(COMPILER_GCC)
188#endif  // !defined(UNLIKELY)
189
190#endif  // BASE_COMPILER_SPECIFIC_H_
191