about summary refs log tree commit diff
path: root/third_party/abseil_cpp/absl/base/macros.h
blob: 3e085a916bbe0d86cde7a9813bae8ca84c579d0e (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
//
// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//
// -----------------------------------------------------------------------------
// File: macros.h
// -----------------------------------------------------------------------------
//
// This header file defines the set of language macros used within Abseil code.
// For the set of macros used to determine supported compilers and platforms,
// see absl/base/config.h instead.
//
// This code is compiled directly on many platforms, including client
// platforms like Windows, Mac, and embedded systems.  Before making
// any changes here, make sure that you're not breaking any platforms.

#ifndef ABSL_BASE_MACROS_H_
#define ABSL_BASE_MACROS_H_

#include <cassert>
#include <cstddef>

#include "absl/base/attributes.h"
#include "absl/base/config.h"
#include "absl/base/optimization.h"
#include "absl/base/port.h"

// ABSL_ARRAYSIZE()
//
// Returns the number of elements in an array as a compile-time constant, which
// can be used in defining new arrays. If you use this macro on a pointer by
// mistake, you will get a compile-time error.
#define ABSL_ARRAYSIZE(array) \
  (sizeof(::absl::macros_internal::ArraySizeHelper(array)))

namespace absl {
ABSL_NAMESPACE_BEGIN
namespace macros_internal {
// Note: this internal template function declaration is used by ABSL_ARRAYSIZE.
// The function doesn't need a definition, as we only use its type.
template <typename T, size_t N>
auto ArraySizeHelper(const T (&array)[N]) -> char (&)[N];
}  // namespace macros_internal
ABSL_NAMESPACE_END
}  // namespace absl

// ABSL_BAD_CALL_IF()
//
// Used on a function overload to trap bad calls: any call that matches the
// overload will cause a compile-time error. This macro uses a clang-specific
// "enable_if" attribute, as described at
// https://clang.llvm.org/docs/AttributeReference.html#enable-if
//
// Overloads which use this macro should be bracketed by
// `#ifdef ABSL_BAD_CALL_IF`.
//
// Example:
//
//   int isdigit(int c);
//   #ifdef ABSL_BAD_CALL_IF
//   int isdigit(int c)
//     ABSL_BAD_CALL_IF(c <= -1 || c > 255,
//                       "'c' must have the value of an unsigned char or EOF");
//   #endif // ABSL_BAD_CALL_IF
#if ABSL_HAVE_ATTRIBUTE(enable_if)
#define ABSL_BAD_CALL_IF(expr, msg) \
  __attribute__((enable_if(expr, "Bad call trap"), unavailable(msg)))
#endif

// ABSL_ASSERT()
//
// In C++11, `assert` can't be used portably within constexpr functions.
// ABSL_ASSERT functions as a runtime assert but works in C++11 constexpr
// functions.  Example:
//
// constexpr double Divide(double a, double b) {
//   return ABSL_ASSERT(b != 0), a / b;
// }
//
// This macro is inspired by
// https://akrzemi1.wordpress.com/2017/05/18/asserts-in-constexpr-functions/
#if defined(NDEBUG)
#define ABSL_ASSERT(expr) \
  (false ? static_cast<void>(expr) : static_cast<void>(0))
#else
#define ABSL_ASSERT(expr)                           \
  (ABSL_PREDICT_TRUE((expr)) ? static_cast<void>(0) \
                             : [] { assert(false && #expr); }())  // NOLINT
#endif

// `ABSL_INTERNAL_HARDENING_ABORT()` controls how `ABSL_HARDENING_ASSERT()`
// aborts the program in release mode (when NDEBUG is defined). The
// implementation should abort the program as quickly as possible and ideally it
// should not be possible to ignore the abort request.
#if (ABSL_HAVE_BUILTIN(__builtin_trap) &&         \
     ABSL_HAVE_BUILTIN(__builtin_unreachable)) || \
    (defined(__GNUC__) && !defined(__clang__))
#define ABSL_INTERNAL_HARDENING_ABORT() \
  do {                                  \
    __builtin_trap();                   \
    __builtin_unreachable();            \
  } while (false)
#else
#define ABSL_INTERNAL_HARDENING_ABORT() abort()
#endif

// ABSL_HARDENING_ASSERT()
//
// `ABSL_HARDENING_ASSERT()` is like `ABSL_ASSERT()`, but used to implement
// runtime assertions that should be enabled in hardened builds even when
// `NDEBUG` is defined.
//
// When `NDEBUG` is not defined, `ABSL_HARDENING_ASSERT()` is identical to
// `ABSL_ASSERT()`.
//
// See `ABSL_OPTION_HARDENED` in `absl/base/options.h` for more information on
// hardened mode.
#if ABSL_OPTION_HARDENED == 1 && defined(NDEBUG)
#define ABSL_HARDENING_ASSERT(expr)                 \
  (ABSL_PREDICT_TRUE((expr)) ? static_cast<void>(0) \
                             : [] { ABSL_INTERNAL_HARDENING_ABORT(); }())
#else
#define ABSL_HARDENING_ASSERT(expr) ABSL_ASSERT(expr)
#endif

#ifdef ABSL_HAVE_EXCEPTIONS
#define ABSL_INTERNAL_TRY try
#define ABSL_INTERNAL_CATCH_ANY catch (...)
#define ABSL_INTERNAL_RETHROW do { throw; } while (false)
#else  // ABSL_HAVE_EXCEPTIONS
#define ABSL_INTERNAL_TRY if (true)
#define ABSL_INTERNAL_CATCH_ANY else if (false)
#define ABSL_INTERNAL_RETHROW do {} while (false)
#endif  // ABSL_HAVE_EXCEPTIONS

// `ABSL_INTERNAL_UNREACHABLE` is an unreachable statement.  A program which
// reaches one has undefined behavior, and the compiler may optimize
// accordingly.
#if defined(__GNUC__) || ABSL_HAVE_BUILTIN(__builtin_unreachable)
#define ABSL_INTERNAL_UNREACHABLE __builtin_unreachable()
#elif defined(_MSC_VER)
#define ABSL_INTERNAL_UNREACHABLE __assume(0)
#else
#define ABSL_INTERNAL_UNREACHABLE
#endif

#endif  // ABSL_BASE_MACROS_H_