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CPP: Remove unused bit_cast() in basictypes.h.
This was also causing a compilation error with GCC 4.8. This CL also removes basictypes.h.orig accidentally added in the previous revision.pull/567/head
Philippe Liard
14 years ago
committed by
Mihaela Rosca
Mihaela Rosca
3 changed files with 0 additions and 500 deletions
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+0 -368tools/cpp/src/base/basictypes.h.orig
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cpp/src/base/basictypes.h
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| @ -1,368 +0,0 @@ | |||
| // Copyright (c) 2010 The Chromium Authors. All rights reserved. | |||
| // Use of this source code is governed by a BSD-style license that can be | |||
| // found in the LICENSE file. | |||
| #ifndef BASE_BASICTYPES_H_ | |||
| #define BASE_BASICTYPES_H_ | |||
| #pragma once | |||
| #include <limits.h> // So we can set the bounds of our types | |||
| #include <stddef.h> // For size_t | |||
| #include <string.h> // for memcpy | |||
| #ifndef COMPILER_MSVC | |||
| // stdint.h is part of C99 but MSVC doesn't have it. | |||
| #include <stdint.h> // For intptr_t. | |||
| #endif | |||
| #ifdef INT64_MAX | |||
| // INT64_MAX is defined if C99 stdint.h is included; use the | |||
| // native types if available. | |||
| typedef int8_t int8; | |||
| typedef int16_t int16; | |||
| typedef int32_t int32; | |||
| typedef int64_t int64; | |||
| typedef uint8_t uint8; | |||
| typedef uint16_t uint16; | |||
| typedef uint32_t uint32; | |||
| typedef uint64_t uint64; | |||
| const uint8 kuint8max = UINT8_MAX; | |||
| const uint16 kuint16max = UINT16_MAX; | |||
| const uint32 kuint32max = UINT32_MAX; | |||
| const uint64 kuint64max = UINT64_MAX; | |||
| const int8 kint8min = INT8_MIN; | |||
| const int8 kint8max = INT8_MAX; | |||
| const int16 kint16min = INT16_MIN; | |||
| const int16 kint16max = INT16_MAX; | |||
| const int32 kint32min = INT32_MIN; | |||
| const int32 kint32max = INT32_MAX; | |||
| const int64 kint64min = INT64_MIN; | |||
| const int64 kint64max = INT64_MAX; | |||
| #else // !INT64_MAX | |||
| typedef signed char int8; | |||
| typedef short int16; | |||
| // TODO: Remove these type guards. These are to avoid conflicts with | |||
| // obsolete/protypes.h in the Gecko SDK. | |||
| #ifndef _INT32 | |||
| #define _INT32 | |||
| typedef int int32; | |||
| #endif | |||
| // The NSPR system headers define 64-bit as |long| when possible. In order to | |||
| // not have typedef mismatches, we do the same on LP64. | |||
| #if __LP64__ | |||
| typedef long int64; | |||
| #else | |||
| typedef long long int64; | |||
| #endif | |||
| // NOTE: unsigned types are DANGEROUS in loops and other arithmetical | |||
| // places. Use the signed types unless your variable represents a bit | |||
| // pattern (eg a hash value) or you really need the extra bit. Do NOT | |||
| // use 'unsigned' to express "this value should always be positive"; | |||
| // use assertions for this. | |||
| typedef unsigned char uint8; | |||
| typedef unsigned short uint16; | |||
| // TODO: Remove these type guards. These are to avoid conflicts with | |||
| // obsolete/protypes.h in the Gecko SDK. | |||
| #ifndef _UINT32 | |||
| #define _UINT32 | |||
| typedef unsigned int uint32; | |||
| #endif | |||
| // See the comment above about NSPR and 64-bit. | |||
| #if __LP64__ | |||
| typedef unsigned long uint64; | |||
| #else | |||
| typedef unsigned long long uint64; | |||
| #endif | |||
| #endif // !INT64_MAX | |||
| typedef signed char schar; | |||
| // A type to represent a Unicode code-point value. As of Unicode 4.0, | |||
| // such values require up to 21 bits. | |||
| // (For type-checking on pointers, make this explicitly signed, | |||
| // and it should always be the signed version of whatever int32 is.) | |||
| typedef signed int char32; | |||
| // A macro to disallow the copy constructor and operator= functions | |||
| // This should be used in the private: declarations for a class | |||
| #define DISALLOW_COPY_AND_ASSIGN(TypeName) \ | |||
| TypeName(const TypeName&); \ | |||
| void operator=(const TypeName&) | |||
| // An older, deprecated, politically incorrect name for the above. | |||
| // NOTE: The usage of this macro was baned from our code base, but some | |||
| // third_party libraries are yet using it. | |||
| // TODO(tfarina): Figure out how to fix the usage of this macro in the | |||
| // third_party libraries and get rid of it. | |||
| #define DISALLOW_EVIL_CONSTRUCTORS(TypeName) DISALLOW_COPY_AND_ASSIGN(TypeName) | |||
| // A macro to disallow all the implicit constructors, namely the | |||
| // default constructor, copy constructor and operator= functions. | |||
| // | |||
| // This should be used in the private: declarations for a class | |||
| // that wants to prevent anyone from instantiating it. This is | |||
| // especially useful for classes containing only static methods. | |||
| #define DISALLOW_IMPLICIT_CONSTRUCTORS(TypeName) \ | |||
| TypeName(); \ | |||
| DISALLOW_COPY_AND_ASSIGN(TypeName) | |||
| // The arraysize(arr) macro returns the # of elements in an array arr. | |||
| // The expression is a compile-time constant, and therefore can be | |||
| // used in defining new arrays, for example. If you use arraysize on | |||
| // a pointer by mistake, you will get a compile-time error. | |||
| // | |||
| // One caveat is that arraysize() doesn't accept any array of an | |||
| // anonymous type or a type defined inside a function. In these rare | |||
| // cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below. This is | |||
| // due to a limitation in C++'s template system. The limitation might | |||
| // eventually be removed, but it hasn't happened yet. | |||
| // This template function declaration is used in defining arraysize. | |||
| // Note that the function doesn't need an implementation, as we only | |||
| // use its type. | |||
| template <typename T, size_t N> | |||
| char (&ArraySizeHelper(T (&array)[N]))[N]; | |||
| // That gcc wants both of these prototypes seems mysterious. VC, for | |||
| // its part, can't decide which to use (another mystery). Matching of | |||
| // template overloads: the final frontier. | |||
| #ifndef _MSC_VER | |||
| template <typename T, size_t N> | |||
| char (&ArraySizeHelper(const T (&array)[N]))[N]; | |||
| #endif | |||
| #define arraysize(array) (sizeof(ArraySizeHelper(array))) | |||
| // ARRAYSIZE_UNSAFE performs essentially the same calculation as arraysize, | |||
| // but can be used on anonymous types or types defined inside | |||
| // functions. It's less safe than arraysize as it accepts some | |||
| // (although not all) pointers. Therefore, you should use arraysize | |||
| // whenever possible. | |||
| // | |||
| // The expression ARRAYSIZE_UNSAFE(a) is a compile-time constant of type | |||
| // size_t. | |||
| // | |||
| // ARRAYSIZE_UNSAFE catches a few type errors. If you see a compiler error | |||
| // | |||
| // "warning: division by zero in ..." | |||
| // | |||
| // when using ARRAYSIZE_UNSAFE, you are (wrongfully) giving it a pointer. | |||
| // You should only use ARRAYSIZE_UNSAFE on statically allocated arrays. | |||
| // | |||
| // The following comments are on the implementation details, and can | |||
| // be ignored by the users. | |||
| // | |||
| // ARRAYSIZE_UNSAFE(arr) works by inspecting sizeof(arr) (the # of bytes in | |||
| // the array) and sizeof(*(arr)) (the # of bytes in one array | |||
| // element). If the former is divisible by the latter, perhaps arr is | |||
| // indeed an array, in which case the division result is the # of | |||
| // elements in the array. Otherwise, arr cannot possibly be an array, | |||
| // and we generate a compiler error to prevent the code from | |||
| // compiling. | |||
| // | |||
| // Since the size of bool is implementation-defined, we need to cast | |||
| // !(sizeof(a) & sizeof(*(a))) to size_t in order to ensure the final | |||
| // result has type size_t. | |||
| // | |||
| // This macro is not perfect as it wrongfully accepts certain | |||
| // pointers, namely where the pointer size is divisible by the pointee | |||
| // size. Since all our code has to go through a 32-bit compiler, | |||
| // where a pointer is 4 bytes, this means all pointers to a type whose | |||
| // size is 3 or greater than 4 will be (righteously) rejected. | |||
| #define ARRAYSIZE_UNSAFE(a) \ | |||
| ((sizeof(a) / sizeof(*(a))) / \ | |||
| static_cast<size_t>(!(sizeof(a) % sizeof(*(a))))) | |||
| // Use implicit_cast as a safe version of static_cast or const_cast | |||
| // for upcasting in the type hierarchy (i.e. casting a pointer to Foo | |||
| // to a pointer to SuperclassOfFoo or casting a pointer to Foo to | |||
| // a const pointer to Foo). | |||
| // When you use implicit_cast, the compiler checks that the cast is safe. | |||
| // Such explicit implicit_casts are necessary in surprisingly many | |||
| // situations where C++ demands an exact type match instead of an | |||
| // argument type convertable to a target type. | |||
| // | |||
| // The From type can be inferred, so the preferred syntax for using | |||
| // implicit_cast is the same as for static_cast etc.: | |||
| // | |||
| // implicit_cast<ToType>(expr) | |||
| // | |||
| // implicit_cast would have been part of the C++ standard library, | |||
| // but the proposal was submitted too late. It will probably make | |||
| // its way into the language in the future. | |||
| template<typename To, typename From> | |||
| inline To implicit_cast(From const &f) { | |||
| return f; | |||
| } | |||
| // The COMPILE_ASSERT macro can be used to verify that a compile time | |||
| // expression is true. For example, you could use it to verify the | |||
| // size of a static array: | |||
| // | |||
| // COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES, | |||
| // content_type_names_incorrect_size); | |||
| // | |||
| // or to make sure a struct is smaller than a certain size: | |||
| // | |||
| // COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large); | |||
| // | |||
| // The second argument to the macro is the name of the variable. If | |||
| // the expression is false, most compilers will issue a warning/error | |||
| // containing the name of the variable. | |||
| template <bool> | |||
| struct CompileAssert { | |||
| }; | |||
| #undef COMPILE_ASSERT | |||
| #define COMPILE_ASSERT(expr, msg) \ | |||
| typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] | |||
| // Implementation details of COMPILE_ASSERT: | |||
| // | |||
| // - COMPILE_ASSERT works by defining an array type that has -1 | |||
| // elements (and thus is invalid) when the expression is false. | |||
| // | |||
| // - The simpler definition | |||
| // | |||
| // #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1] | |||
| // | |||
| // does not work, as gcc supports variable-length arrays whose sizes | |||
| // are determined at run-time (this is gcc's extension and not part | |||
| // of the C++ standard). As a result, gcc fails to reject the | |||
| // following code with the simple definition: | |||
| // | |||
| // int foo; | |||
| // COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is | |||
| // // not a compile-time constant. | |||
| // | |||
| // - By using the type CompileAssert<(bool(expr))>, we ensures that | |||
| // expr is a compile-time constant. (Template arguments must be | |||
| // determined at compile-time.) | |||
| // | |||
| // - The outter parentheses in CompileAssert<(bool(expr))> are necessary | |||
| // to work around a bug in gcc 3.4.4 and 4.0.1. If we had written | |||
| // | |||
| // CompileAssert<bool(expr)> | |||
| // | |||
| // instead, these compilers will refuse to compile | |||
| // | |||
| // COMPILE_ASSERT(5 > 0, some_message); | |||
| // | |||
| // (They seem to think the ">" in "5 > 0" marks the end of the | |||
| // template argument list.) | |||
| // | |||
| // - The array size is (bool(expr) ? 1 : -1), instead of simply | |||
| // | |||
| // ((expr) ? 1 : -1). | |||
| // | |||
| // This is to avoid running into a bug in MS VC 7.1, which | |||
| // causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1. | |||
| // bit_cast<Dest,Source> is a template function that implements the | |||
| // equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in | |||
| // very low-level functions like the protobuf library and fast math | |||
| // support. | |||
| // | |||
| // float f = 3.14159265358979; | |||
| // int i = bit_cast<int32>(f); | |||
| // // i = 0x40490fdb | |||
| // | |||
| // The classical address-casting method is: | |||
| // | |||
| // // WRONG | |||
| // float f = 3.14159265358979; // WRONG | |||
| // int i = * reinterpret_cast<int*>(&f); // WRONG | |||
| // | |||
| // The address-casting method actually produces undefined behavior | |||
| // according to ISO C++ specification section 3.10 -15 -. Roughly, this | |||
| // section says: if an object in memory has one type, and a program | |||
| // accesses it with a different type, then the result is undefined | |||
| // behavior for most values of "different type". | |||
| // | |||
| // This is true for any cast syntax, either *(int*)&f or | |||
| // *reinterpret_cast<int*>(&f). And it is particularly true for | |||
| // conversions betweeen integral lvalues and floating-point lvalues. | |||
| // | |||
| // The purpose of 3.10 -15- is to allow optimizing compilers to assume | |||
| // that expressions with different types refer to different memory. gcc | |||
| // 4.0.1 has an optimizer that takes advantage of this. So a | |||
| // non-conforming program quietly produces wildly incorrect output. | |||
| // | |||
| // The problem is not the use of reinterpret_cast. The problem is type | |||
| // punning: holding an object in memory of one type and reading its bits | |||
| // back using a different type. | |||
| // | |||
| // The C++ standard is more subtle and complex than this, but that | |||
| // is the basic idea. | |||
| // | |||
| // Anyways ... | |||
| // | |||
| // bit_cast<> calls memcpy() which is blessed by the standard, | |||
| // especially by the example in section 3.9 . Also, of course, | |||
| // bit_cast<> wraps up the nasty logic in one place. | |||
| // | |||
| // Fortunately memcpy() is very fast. In optimized mode, with a | |||
| // constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline | |||
| // code with the minimal amount of data movement. On a 32-bit system, | |||
| // memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8) | |||
| // compiles to two loads and two stores. | |||
| // | |||
| // I tested this code with gcc 2.95.3, gcc 4.0.1, icc 8.1, and msvc 7.1. | |||
| // | |||
| // WARNING: if Dest or Source is a non-POD type, the result of the memcpy | |||
| // is likely to surprise you. | |||
| template <class Dest, class Source> | |||
| inline Dest bit_cast(const Source& source) { | |||
| // Compile time assertion: sizeof(Dest) == sizeof(Source) | |||
| // A compile error here means your Dest and Source have different sizes. | |||
| typedef char VerifySizesAreEqual [sizeof(Dest) == sizeof(Source) ? 1 : -1]; | |||
| Dest dest; | |||
| memcpy(&dest, &source, sizeof(dest)); | |||
| return dest; | |||
| } | |||
| // Used to explicitly mark the return value of a function as unused. If you are | |||
| // really sure you don't want to do anything with the return value of a function | |||
| // that has been marked WARN_UNUSED_RESULT, wrap it with this. Example: | |||
| // | |||
| // scoped_ptr<MyType> my_var = ...; | |||
| // if (TakeOwnership(my_var.get()) == SUCCESS) | |||
| // ignore_result(my_var.release()); | |||
| // | |||
| template<typename T> | |||
| inline void ignore_result(const T& ignored) { | |||
| } | |||
| // The following enum should be used only as a constructor argument to indicate | |||
| // that the variable has static storage class, and that the constructor should | |||
| // do nothing to its state. It indicates to the reader that it is legal to | |||
| // declare a static instance of the class, provided the constructor is given | |||
| // the base::LINKER_INITIALIZED argument. Normally, it is unsafe to declare a | |||
| // static variable that has a constructor or a destructor because invocation | |||
| // order is undefined. However, IF the type can be initialized by filling with | |||
| // zeroes (which the loader does for static variables), AND the destructor also | |||
| // does nothing to the storage, AND there are no virtual methods, then a | |||
| // constructor declared as | |||
| // explicit MyClass(base::LinkerInitialized x) {} | |||
| // and invoked as | |||
| // static MyClass my_variable_name(base::LINKER_INITIALIZED); | |||
| namespace base { | |||
| enum LinkerInitialized { LINKER_INITIALIZED }; | |||
| } // base | |||
| #endif // BASE_BASICTYPES_H_ | |||