// Copyright 2014 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_BASE_MACROS_H_
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#define V8_BASE_MACROS_H_
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#include <limits>
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#include "src/base/compiler-specific.h"
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#include "src/base/format-macros.h"
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#include "src/base/logging.h"
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// No-op macro which is used to work around MSVC's funky VA_ARGS support.
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#define EXPAND(x) x
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// TODO(all) Replace all uses of this macro with C++'s offsetof. To do that, we
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// have to make sure that only standard-layout types and simple field
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// designators are used.
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#define OFFSET_OF(type, field) \
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(reinterpret_cast<intptr_t>(&(reinterpret_cast<type*>(16)->field)) - 16)
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// The arraysize(arr) macro returns the # of elements in an array arr.
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// The expression is a compile-time constant, and therefore can be
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// used in defining new arrays, for example. If you use arraysize on
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// a pointer by mistake, you will get a compile-time error.
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#define arraysize(array) (sizeof(ArraySizeHelper(array)))
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// This template function declaration is used in defining arraysize.
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// Note that the function doesn't need an implementation, as we only
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// use its type.
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template <typename T, size_t N>
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char (&ArraySizeHelper(T (&array)[N]))[N];
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#if !V8_CC_MSVC
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// That gcc wants both of these prototypes seems mysterious. VC, for
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// its part, can't decide which to use (another mystery). Matching of
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// template overloads: the final frontier.
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template <typename T, size_t N>
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char (&ArraySizeHelper(const T (&array)[N]))[N];
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#endif
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// bit_cast<Dest,Source> is a template function that implements the
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// equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in
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// very low-level functions like the protobuf library and fast math
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// support.
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//
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// float f = 3.14159265358979;
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// int i = bit_cast<int32>(f);
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// // i = 0x40490fdb
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//
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// The classical address-casting method is:
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//
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// // WRONG
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// float f = 3.14159265358979; // WRONG
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// int i = * reinterpret_cast<int*>(&f); // WRONG
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//
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// The address-casting method actually produces undefined behavior
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// according to ISO C++ specification section 3.10 -15 -. Roughly, this
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// section says: if an object in memory has one type, and a program
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// accesses it with a different type, then the result is undefined
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// behavior for most values of "different type".
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//
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// This is true for any cast syntax, either *(int*)&f or
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// *reinterpret_cast<int*>(&f). And it is particularly true for
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// conversions between integral lvalues and floating-point lvalues.
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//
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// The purpose of 3.10 -15- is to allow optimizing compilers to assume
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// that expressions with different types refer to different memory. gcc
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// 4.0.1 has an optimizer that takes advantage of this. So a
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// non-conforming program quietly produces wildly incorrect output.
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//
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// The problem is not the use of reinterpret_cast. The problem is type
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// punning: holding an object in memory of one type and reading its bits
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// back using a different type.
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//
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// The C++ standard is more subtle and complex than this, but that
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// is the basic idea.
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//
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// Anyways ...
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//
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// bit_cast<> calls memcpy() which is blessed by the standard,
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// especially by the example in section 3.9 . Also, of course,
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// bit_cast<> wraps up the nasty logic in one place.
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//
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// Fortunately memcpy() is very fast. In optimized mode, with a
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// constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline
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// code with the minimal amount of data movement. On a 32-bit system,
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// memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8)
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// compiles to two loads and two stores.
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//
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// I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1.
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//
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// WARNING: if Dest or Source is a non-POD type, the result of the memcpy
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// is likely to surprise you.
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template <class Dest, class Source>
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V8_INLINE Dest bit_cast(Source const& source) {
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static_assert(sizeof(Dest) == sizeof(Source),
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"source and dest must be same size");
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Dest dest;
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memcpy(&dest, &source, sizeof(dest));
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return dest;
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}
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// Explicitly declare the assignment operator as deleted.
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#define DISALLOW_ASSIGN(TypeName) TypeName& operator=(const TypeName&) = delete;
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// Explicitly declare the copy constructor and assignment operator as deleted.
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#define DISALLOW_COPY_AND_ASSIGN(TypeName) \
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TypeName(const TypeName&) = delete; \
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DISALLOW_ASSIGN(TypeName)
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// Explicitly declare all copy/move constructors and assignments as deleted.
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#define DISALLOW_COPY_AND_MOVE_AND_ASSIGN(TypeName) \
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TypeName(TypeName&&) = delete; \
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TypeName& operator=(TypeName&&) = delete; \
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DISALLOW_COPY_AND_ASSIGN(TypeName)
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// Explicitly declare all implicit constructors as deleted, namely the
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// default constructor, copy constructor and operator= functions.
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// This is especially useful for classes containing only static methods.
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#define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \
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TypeName() = delete; \
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DISALLOW_COPY_AND_ASSIGN(TypeName)
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// Disallow copying a type, but provide default construction, move construction
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// and move assignment. Especially useful for move-only structs.
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#define MOVE_ONLY_WITH_DEFAULT_CONSTRUCTORS(TypeName) \
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TypeName() = default; \
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MOVE_ONLY_NO_DEFAULT_CONSTRUCTOR(TypeName)
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// Disallow copying a type, and only provide move construction and move
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// assignment. Especially useful for move-only structs.
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#define MOVE_ONLY_NO_DEFAULT_CONSTRUCTOR(TypeName) \
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TypeName(TypeName&&) V8_NOEXCEPT = default; \
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TypeName& operator=(TypeName&&) V8_NOEXCEPT = default; \
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DISALLOW_COPY_AND_ASSIGN(TypeName)
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// A macro to disallow the dynamic allocation.
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// This should be used in the private: declarations for a class
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// Declaring operator new and delete as deleted is not spec compliant.
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// Extract from 3.2.2 of C++11 spec:
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// [...] A non-placement deallocation function for a class is
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// odr-used by the definition of the destructor of that class, [...]
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#define DISALLOW_NEW_AND_DELETE() \
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void* operator new(size_t) { base::OS::Abort(); } \
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void* operator new[](size_t) { base::OS::Abort(); }; \
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void operator delete(void*, size_t) { base::OS::Abort(); } \
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void operator delete[](void*, size_t) { base::OS::Abort(); }
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// Define V8_USE_ADDRESS_SANITIZER macro.
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#if defined(__has_feature)
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#if __has_feature(address_sanitizer)
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#define V8_USE_ADDRESS_SANITIZER 1
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#endif
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#endif
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// Define DISABLE_ASAN macro.
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#ifdef V8_USE_ADDRESS_SANITIZER
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#define DISABLE_ASAN __attribute__((no_sanitize_address))
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#else
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#define DISABLE_ASAN
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#endif
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// Define V8_USE_MEMORY_SANITIZER macro.
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#if defined(__has_feature)
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#if __has_feature(memory_sanitizer)
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#define V8_USE_MEMORY_SANITIZER 1
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#endif
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#endif
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// Helper macro to define no_sanitize attributes only with clang.
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#if defined(__clang__) && defined(__has_attribute)
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#if __has_attribute(no_sanitize)
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#define CLANG_NO_SANITIZE(what) __attribute__((no_sanitize(what)))
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#endif
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#endif
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#if !defined(CLANG_NO_SANITIZE)
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#define CLANG_NO_SANITIZE(what)
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#endif
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// DISABLE_CFI_PERF -- Disable Control Flow Integrity checks for Perf reasons.
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#define DISABLE_CFI_PERF CLANG_NO_SANITIZE("cfi")
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// DISABLE_CFI_ICALL -- Disable Control Flow Integrity indirect call checks,
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// useful because calls into JITed code can not be CFI verified.
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#define DISABLE_CFI_ICALL CLANG_NO_SANITIZE("cfi-icall")
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#if V8_CC_GNU
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#define V8_IMMEDIATE_CRASH() __builtin_trap()
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#else
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#define V8_IMMEDIATE_CRASH() ((void(*)())0)()
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#endif
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// TODO(all) Replace all uses of this macro with static_assert, remove macro.
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#define STATIC_ASSERT(test) static_assert(test, #test)
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namespace v8 {
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namespace base {
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// Note that some implementations of std::is_trivially_copyable mandate that at
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// least one of the copy constructor, move constructor, copy assignment or move
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// assignment is non-deleted, while others do not. Be aware that also
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// base::is_trivially_copyable will differ for these cases.
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template <typename T>
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struct is_trivially_copyable {
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#if V8_CC_MSVC
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// Unfortunately, MSVC 2015 is broken in that std::is_trivially_copyable can
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// be false even though it should be true according to the standard.
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// (status at 2018-02-26, observed on the msvc waterfall bot).
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// Interestingly, the lower-level primitives used below are working as
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// intended, so we reimplement this according to the standard.
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// See also https://developercommunity.visualstudio.com/content/problem/
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// 170883/msvc-type-traits-stdis-trivial-is-bugged.html.
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static constexpr bool value =
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// Copy constructor is trivial or deleted.
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(std::is_trivially_copy_constructible<T>::value ||
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!std::is_copy_constructible<T>::value) &&
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// Copy assignment operator is trivial or deleted.
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(std::is_trivially_copy_assignable<T>::value ||
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!std::is_copy_assignable<T>::value) &&
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// Move constructor is trivial or deleted.
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(std::is_trivially_move_constructible<T>::value ||
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!std::is_move_constructible<T>::value) &&
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// Move assignment operator is trivial or deleted.
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(std::is_trivially_move_assignable<T>::value ||
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!std::is_move_assignable<T>::value) &&
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// (Some implementations mandate that one of the above is non-deleted, but
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// the standard does not, so let's skip this check.)
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// Trivial non-deleted destructor.
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std::is_trivially_destructible<T>::value;
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#elif defined(__GNUC__) && __GNUC__ < 5
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// WARNING:
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// On older libstdc++ versions, there is no way to correctly implement
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// is_trivially_copyable. The workaround below is an approximation (neither
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// over- nor underapproximation). E.g. it wrongly returns true if the move
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// constructor is non-trivial, and it wrongly returns false if the copy
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// constructor is deleted, but copy assignment is trivial.
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// TODO(rongjie) Remove this workaround once we require gcc >= 5.0
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static constexpr bool value =
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__has_trivial_copy(T) && __has_trivial_destructor(T);
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#else
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static constexpr bool value = std::is_trivially_copyable<T>::value;
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#endif
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};
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#if defined(__GNUC__) && __GNUC__ < 5
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// On older libstdc++ versions, base::is_trivially_copyable<T>::value is only an
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// approximation (see above), so make ASSERT_{NOT_,}TRIVIALLY_COPYABLE a noop.
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#define ASSERT_TRIVIALLY_COPYABLE(T) static_assert(true, "check disabled")
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#define ASSERT_NOT_TRIVIALLY_COPYABLE(T) static_assert(true, "check disabled")
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#else
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#define ASSERT_TRIVIALLY_COPYABLE(T) \
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static_assert(::v8::base::is_trivially_copyable<T>::value, \
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#T " should be trivially copyable")
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#define ASSERT_NOT_TRIVIALLY_COPYABLE(T) \
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static_assert(!::v8::base::is_trivially_copyable<T>::value, \
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#T " should not be trivially copyable")
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#endif
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// The USE(x, ...) template is used to silence C++ compiler warnings
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// issued for (yet) unused variables (typically parameters).
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// The arguments are guaranteed to be evaluated from left to right.
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struct Use {
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template <typename T>
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Use(T&&) {} // NOLINT(runtime/explicit)
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};
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#define USE(...) \
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do { \
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::v8::base::Use unused_tmp_array_for_use_macro[]{__VA_ARGS__}; \
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(void)unused_tmp_array_for_use_macro; \
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} while (false)
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} // namespace base
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} // namespace v8
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// implicit_cast<A>(x) triggers an implicit cast from {x} to type {A}. This is
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// useful in situations where static_cast<A>(x) would do too much.
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// Only use this for cheap-to-copy types, or use move semantics explicitly.
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template <class A>
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V8_INLINE A implicit_cast(A x) {
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return x;
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}
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// Define our own macros for writing 64-bit constants. This is less fragile
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// than defining __STDC_CONSTANT_MACROS before including <stdint.h>, and it
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// works on compilers that don't have it (like MSVC).
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#if V8_CC_MSVC
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# if V8_HOST_ARCH_64_BIT
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# define V8_PTR_PREFIX "ll"
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# else
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# define V8_PTR_PREFIX ""
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# endif // V8_HOST_ARCH_64_BIT
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#elif V8_CC_MINGW64
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# define V8_PTR_PREFIX "I64"
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#elif V8_HOST_ARCH_64_BIT
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# define V8_PTR_PREFIX "l"
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#else
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#if V8_OS_AIX
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#define V8_PTR_PREFIX "l"
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#else
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# define V8_PTR_PREFIX ""
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#endif
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#endif
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#define V8PRIxPTR V8_PTR_PREFIX "x"
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#define V8PRIdPTR V8_PTR_PREFIX "d"
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#define V8PRIuPTR V8_PTR_PREFIX "u"
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#ifdef V8_TARGET_ARCH_64_BIT
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#define V8_PTR_HEX_DIGITS 12
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#define V8PRIxPTR_FMT "0x%012" V8PRIxPTR
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#else
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#define V8_PTR_HEX_DIGITS 8
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#define V8PRIxPTR_FMT "0x%08" V8PRIxPTR
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#endif
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// ptrdiff_t is 't' according to the standard, but MSVC uses 'I'.
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#if V8_CC_MSVC
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#define V8PRIxPTRDIFF "Ix"
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#define V8PRIdPTRDIFF "Id"
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#define V8PRIuPTRDIFF "Iu"
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#else
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#define V8PRIxPTRDIFF "tx"
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#define V8PRIdPTRDIFF "td"
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#define V8PRIuPTRDIFF "tu"
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#endif
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// Fix for Mac OS X defining uintptr_t as "unsigned long":
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#if V8_OS_MACOSX
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#undef V8PRIxPTR
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#define V8PRIxPTR "lx"
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#undef V8PRIdPTR
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#define V8PRIdPTR "ld"
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#undef V8PRIuPTR
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#define V8PRIuPTR "lxu"
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#endif
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// The following macro works on both 32 and 64-bit platforms.
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// Usage: instead of writing 0x1234567890123456
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// write V8_2PART_UINT64_C(0x12345678,90123456);
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#define V8_2PART_UINT64_C(a, b) (((static_cast<uint64_t>(a) << 32) + 0x##b##u))
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// Compute the 0-relative offset of some absolute value x of type T.
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// This allows conversion of Addresses and integral types into
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// 0-relative int offsets.
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template <typename T>
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constexpr inline intptr_t OffsetFrom(T x) {
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return x - static_cast<T>(0);
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}
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// Compute the absolute value of type T for some 0-relative offset x.
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// This allows conversion of 0-relative int offsets into Addresses and
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// integral types.
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template <typename T>
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constexpr inline T AddressFrom(intptr_t x) {
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return static_cast<T>(static_cast<T>(0) + x);
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}
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// Return the largest multiple of m which is <= x.
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template <typename T>
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inline T RoundDown(T x, intptr_t m) {
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// m must be a power of two.
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DCHECK(m != 0 && ((m & (m - 1)) == 0));
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return AddressFrom<T>(OffsetFrom(x) & -m);
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}
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template <intptr_t m, typename T>
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constexpr inline T RoundDown(T x) {
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// m must be a power of two.
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STATIC_ASSERT(m != 0 && ((m & (m - 1)) == 0));
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return AddressFrom<T>(OffsetFrom(x) & -m);
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}
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// Return the smallest multiple of m which is >= x.
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template <typename T>
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inline T RoundUp(T x, intptr_t m) {
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return RoundDown<T>(static_cast<T>(x + m - 1), m);
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}
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template <intptr_t m, typename T>
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constexpr inline T RoundUp(T x) {
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return RoundDown<m, T>(static_cast<T>(x + m - 1));
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}
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inline void* AlignedAddress(void* address, size_t alignment) {
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// The alignment must be a power of two.
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DCHECK_EQ(alignment & (alignment - 1), 0u);
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return reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(address) &
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~static_cast<uintptr_t>(alignment - 1));
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}
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// Bounds checks for float to integer conversions, which does truncation. Hence,
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// the range of legal values is (min - 1, max + 1).
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template <typename int_t, typename float_t, typename biggest_int_t = int64_t>
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bool is_inbounds(float_t v) {
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static_assert(sizeof(int_t) < sizeof(biggest_int_t),
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"int_t can't be bounds checked by the compiler");
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constexpr float_t kLowerBound =
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static_cast<float_t>(std::numeric_limits<int_t>::min()) - 1;
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constexpr float_t kUpperBound =
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static_cast<float_t>(std::numeric_limits<int_t>::max()) + 1;
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constexpr bool kLowerBoundIsMin =
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static_cast<biggest_int_t>(kLowerBound) ==
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static_cast<biggest_int_t>(std::numeric_limits<int_t>::min());
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constexpr bool kUpperBoundIsMax =
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static_cast<biggest_int_t>(kUpperBound) ==
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static_cast<biggest_int_t>(std::numeric_limits<int_t>::max());
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return (kLowerBoundIsMin ? (kLowerBound <= v) : (kLowerBound < v)) &&
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(kUpperBoundIsMax ? (v <= kUpperBound) : (v < kUpperBound));
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}
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#ifdef V8_OS_WIN
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// Setup for Windows shared library export.
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#ifdef BUILDING_V8_SHARED
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#define V8_EXPORT_PRIVATE __declspec(dllexport)
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#elif USING_V8_SHARED
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#define V8_EXPORT_PRIVATE __declspec(dllimport)
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#else
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#define V8_EXPORT_PRIVATE
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#endif // BUILDING_V8_SHARED
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#else // V8_OS_WIN
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// Setup for Linux shared library export.
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#if V8_HAS_ATTRIBUTE_VISIBILITY
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#ifdef BUILDING_V8_SHARED
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#define V8_EXPORT_PRIVATE __attribute__((visibility("default")))
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#else
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#define V8_EXPORT_PRIVATE
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#endif
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#else
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#define V8_EXPORT_PRIVATE
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#endif
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#endif // V8_OS_WIN
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#endif // V8_BASE_MACROS_H_
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