1// Copyright 2014 the V8 project 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 V8_BASE_COMPILER_SPECIFIC_H_
6#define V8_BASE_COMPILER_SPECIFIC_H_
7
8#include "include/v8config.h"
9
10// Annotation to silence compiler warnings about unused
11// types/functions/variables. Use like:
12//
13//   using V8_ALLOW_UNUSED Bar = Foo;
14//   V8_ALLOW_UNUSED void foo() {}
15#if V8_HAS_ATTRIBUTE_UNUSED
16#define V8_ALLOW_UNUSED __attribute__((unused))
17#else
18#define V8_ALLOW_UNUSED
19#endif
20
21// Tell the compiler a function is using a printf-style format string.
22// |format_param| is the one-based index of the format string parameter;
23// |dots_param| is the one-based index of the "..." parameter.
24// For v*printf functions (which take a va_list), pass 0 for dots_param.
25// (This is undocumented but matches what the system C headers do.)
26#if defined(__GNUC__)
27#define PRINTF_FORMAT(format_param, dots_param) \
28  __attribute__((format(printf, format_param, dots_param)))
29#else
30#define PRINTF_FORMAT(format_param, dots_param)
31#endif
32
33// The C++ standard requires that static const members have an out-of-class
34// definition (in a single compilation unit), but MSVC chokes on this (when
35// language extensions, which are required, are enabled). (You're only likely to
36// notice the need for a definition if you take the address of the member or,
37// more commonly, pass it to a function that takes it as a reference argument --
38// probably an STL function.) This macro makes MSVC do the right thing. See
39// http://msdn.microsoft.com/en-us/library/34h23df8(v=vs.100).aspx for more
40// information. Use like:
41//
42// In .h file:
43//   struct Foo {
44//     static const int kBar = 5;
45//   };
46//
47// In .cc file:
48//   STATIC_CONST_MEMBER_DEFINITION const int Foo::kBar;
49#if V8_HAS_DECLSPEC_SELECTANY
50#define STATIC_CONST_MEMBER_DEFINITION __declspec(selectany)
51#else
52#define STATIC_CONST_MEMBER_DEFINITION
53#endif
54
55#if V8_CC_MSVC
56
57#include <sal.h>
58
59// Macros for suppressing and disabling warnings on MSVC.
60//
61// Warning numbers are enumerated at:
62// http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
63//
64// The warning pragma:
65// http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
66//
67// Using __pragma instead of #pragma inside macros:
68// http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
69
70// MSVC_SUPPRESS_WARNING disables warning |n| for the remainder of the line and
71// for the next line of the source file.
72#define MSVC_SUPPRESS_WARNING(n) __pragma(warning(suppress : n))
73
74// Allows exporting a class that inherits from a non-exported base class.
75// This uses suppress instead of push/pop because the delimiter after the
76// declaration (either "," or "{") has to be placed before the pop macro.
77//
78// Example usage:
79// class EXPORT_API Foo : NON_EXPORTED_BASE(public Bar) {
80//
81// MSVC Compiler warning C4275:
82// non dll-interface class 'Bar' used as base for dll-interface class 'Foo'.
83// Note that this is intended to be used only when no access to the base class'
84// static data is done through derived classes or inline methods. For more info,
85// see http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
86#define NON_EXPORTED_BASE(code) \
87  MSVC_SUPPRESS_WARNING(4275)   \
88  code
89
90#else  // Not MSVC
91
92#define MSVC_SUPPRESS_WARNING(n)
93#define NON_EXPORTED_BASE(code) code
94
95#endif  // V8_CC_MSVC
96
97// Allowing the use of noexcept by removing the keyword on older compilers that
98// do not support adding noexcept to default members.
99// Disabled on MSVC because constructors of standard containers are not noexcept
100// there.
101#if ((!defined(V8_CC_GNU) && !defined(V8_CC_MSVC) &&                      \
102      !defined(V8_TARGET_ARCH_MIPS) && !defined(V8_TARGET_ARCH_MIPS64) && \
103      !defined(V8_TARGET_ARCH_PPC) && !defined(V8_TARGET_ARCH_PPC64) &&   \
104      !defined(V8_TARGET_ARCH_RISCV64)) ||                                \
105     (defined(__clang__) && __cplusplus > 201300L))
106#define V8_NOEXCEPT noexcept
107#else
108#define V8_NOEXCEPT
109#endif
110
111// Specify memory alignment for structs, classes, etc.
112// Use like:
113//   class ALIGNAS(16) MyClass { ... }
114//   ALIGNAS(16) int array[4];
115//
116// In most places you can use the C++11 keyword "alignas", which is preferred.
117//
118// But compilers have trouble mixing __attribute__((...)) syntax with
119// alignas(...) syntax.
120//
121// Doesn't work in clang or gcc:
122//   struct alignas(16) __attribute__((packed)) S { char c; };
123// Works in clang but not gcc:
124//   struct __attribute__((packed)) alignas(16) S2 { char c; };
125// Works in clang and gcc:
126//   struct alignas(16) S3 { char c; } __attribute__((packed));
127//
128// There are also some attributes that must be specified *before* a class
129// definition: visibility (used for exporting functions/classes) is one of
130// these attributes. This means that it is not possible to use alignas() with a
131// class that is marked as exported.
132#if defined(V8_CC_MSVC)
133#define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
134#else
135#define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
136#endif
137
138#endif  // V8_BASE_COMPILER_SPECIFIC_H_
139