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Diffstat (limited to 'mfbt/Attributes.h')
| -rw-r--r-- | mfbt/Attributes.h | 498 |
1 files changed, 498 insertions, 0 deletions
diff --git a/mfbt/Attributes.h b/mfbt/Attributes.h new file mode 100644 index 0000000..8c5d49f --- /dev/null +++ b/mfbt/Attributes.h @@ -0,0 +1,498 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */ + +/* Implementations of various class and method modifier attributes. */ + +#ifndef mozilla_Attributes_h_ +#define mozilla_Attributes_h_ + +/* + * This header does not include any other headers so that it can be included by + * code that is (only currently) mfbt-incompatible. + */ + +/* Suppress any warnings about c++0x extensions. */ +#if defined(__clang__) +# pragma clang diagnostic ignored "-Wc++0x-extensions" +#endif + +/* + * MOZ_INLINE is a macro which expands to tell the compiler that the method + * decorated with it should be inlined. This macro is usable from C and C++ + * code, even though C89 does not support the |inline| keyword. The compiler + * may ignore this directive if it chooses. + */ +#if defined(__cplusplus) +# define MOZ_INLINE inline +#elif defined(_MSC_VER) +# define MOZ_INLINE __inline +#elif defined(__GNUC__) +# define MOZ_INLINE __inline__ +#else +# define MOZ_INLINE inline +#endif + +/* + * MOZ_ALWAYS_INLINE is a macro which expands to tell the compiler that the + * method decorated with it must be inlined, even if the compiler thinks + * otherwise. This is only a (much) stronger version of the MOZ_INLINE hint: + * compilers are not guaranteed to respect it (although they're much more likely + * to do so). + */ +#if defined(DEBUG) +# define MOZ_ALWAYS_INLINE MOZ_INLINE +#elif defined(_MSC_VER) +# define MOZ_ALWAYS_INLINE __forceinline +#elif defined(__GNUC__) +# define MOZ_ALWAYS_INLINE __attribute__((always_inline)) MOZ_INLINE +#else +# define MOZ_ALWAYS_INLINE MOZ_INLINE +#endif + +/* + * g++ requires -std=c++0x or -std=gnu++0x to support C++11 functionality + * without warnings (functionality used by the macros below). These modes are + * detectable by checking whether __GXX_EXPERIMENTAL_CXX0X__ is defined or, more + * standardly, by checking whether __cplusplus has a C++11 or greater value. + * Current versions of g++ do not correctly set __cplusplus, so we check both + * for forward compatibility. + */ +#if defined(__clang__) + /* + * Per Clang documentation, "Note that marketing version numbers should not + * be used to check for language features, as different vendors use different + * numbering schemes. Instead, use the feature checking macros." + */ +# ifndef __has_extension +# define __has_extension __has_feature /* compatibility, for older versions of clang */ +# endif +# if __has_extension(cxx_deleted_functions) +# define MOZ_HAVE_CXX11_DELETE +# endif +# if __has_extension(cxx_override_control) +# define MOZ_HAVE_CXX11_OVERRIDE +# define MOZ_HAVE_CXX11_FINAL final +# endif +# if __has_extension(cxx_strong_enums) +# define MOZ_HAVE_CXX11_ENUM_TYPE +# define MOZ_HAVE_CXX11_STRONG_ENUMS +# endif +# if __has_attribute(noinline) +# define MOZ_HAVE_NEVER_INLINE __attribute__((noinline)) +# endif +# if __has_attribute(noreturn) +# define MOZ_HAVE_NORETURN __attribute__((noreturn)) +# endif +#elif defined(__GNUC__) +# if defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L +# if __GNUC__ > 4 +# define MOZ_HAVE_CXX11_DELETE +# define MOZ_HAVE_CXX11_OVERRIDE +# define MOZ_HAVE_CXX11_FINAL final +# elif __GNUC__ == 4 +# if __GNUC_MINOR__ >= 7 +# define MOZ_HAVE_CXX11_OVERRIDE +# define MOZ_HAVE_CXX11_FINAL final +# endif +# if __GNUC_MINOR__ >= 4 +# define MOZ_HAVE_CXX11_DELETE +# define MOZ_HAVE_CXX11_ENUM_TYPE +# define MOZ_HAVE_CXX11_STRONG_ENUMS +# endif +# endif +# else + /* __final is a non-C++11 GCC synonym for 'final', per GCC r176655. */ +# if __GNUC__ > 4 +# define MOZ_HAVE_CXX11_FINAL __final +# elif __GNUC__ == 4 +# if __GNUC_MINOR__ >= 7 +# define MOZ_HAVE_CXX11_FINAL __final +# endif +# endif +# endif +# define MOZ_HAVE_NEVER_INLINE __attribute__((noinline)) +# define MOZ_HAVE_NORETURN __attribute__((noreturn)) +#elif defined(_MSC_VER) +# if _MSC_VER >= 1400 +# define MOZ_HAVE_CXX11_OVERRIDE + /* MSVC currently spells "final" as "sealed". */ +# define MOZ_HAVE_CXX11_FINAL sealed +# define MOZ_HAVE_CXX11_ENUM_TYPE +# endif +# if _MSC_VER >= 1700 +# define MOZ_HAVE_CXX11_STRONG_ENUMS +# endif +# define MOZ_HAVE_NEVER_INLINE __declspec(noinline) +# define MOZ_HAVE_NORETURN __declspec(noreturn) +#endif + +/* + * MOZ_NEVER_INLINE is a macro which expands to tell the compiler that the + * method decorated with it must never be inlined, even if the compiler would + * otherwise choose to inline the method. Compilers aren't absolutely + * guaranteed to support this, but most do. + */ +#if defined(MOZ_HAVE_NEVER_INLINE) +# define MOZ_NEVER_INLINE MOZ_HAVE_NEVER_INLINE +#else +# define MOZ_NEVER_INLINE /* no support */ +#endif + +/* + * MOZ_NORETURN, specified at the start of a function declaration, indicates + * that the given function does not return. (The function definition does not + * need to be annotated.) + * + * MOZ_NORETURN void abort(const char* msg); + * + * This modifier permits the compiler to optimize code assuming a call to such a + * function will never return. It also enables the compiler to avoid spurious + * warnings about not initializing variables, or about any other seemingly-dodgy + * operations performed after the function returns. + * + * This modifier does not affect the corresponding function's linking behavior. + */ +#if defined(MOZ_HAVE_NORETURN) +# define MOZ_NORETURN MOZ_HAVE_NORETURN +#else +# define MOZ_NORETURN /* no support */ +#endif + +/* + * MOZ_ASAN_BLACKLIST is a macro to tell AddressSanitizer (a compile-time + * instrumentation shipped with Clang) to not instrument the annotated function. + * Furthermore, it will prevent the compiler from inlining the function because + * inlining currently breaks the blacklisting mechanism of AddressSanitizer. + */ +#if defined(MOZ_ASAN) +# define MOZ_ASAN_BLACKLIST MOZ_NEVER_INLINE __attribute__((no_address_safety_analysis)) +# else +# define MOZ_ASAN_BLACKLIST +#endif + + +#ifdef __cplusplus + +/* + * MOZ_DELETE, specified immediately prior to the ';' terminating an undefined- + * method declaration, attempts to delete that method from the corresponding + * class. An attempt to use the method will always produce an error *at compile + * time* (instead of sometimes as late as link time) when this macro can be + * implemented. For example, you can use MOZ_DELETE to produce classes with no + * implicit copy constructor or assignment operator: + * + * struct NonCopyable + * { + * private: + * NonCopyable(const NonCopyable& other) MOZ_DELETE; + * void operator=(const NonCopyable& other) MOZ_DELETE; + * }; + * + * If MOZ_DELETE can't be implemented for the current compiler, use of the + * annotated method will still cause an error, but the error might occur at link + * time in some cases rather than at compile time. + * + * MOZ_DELETE relies on C++11 functionality not universally implemented. As a + * backstop, method declarations using MOZ_DELETE should be private. + */ +#if defined(MOZ_HAVE_CXX11_DELETE) +# define MOZ_DELETE = delete +#else +# define MOZ_DELETE /* no support */ +#endif + +/* + * MOZ_OVERRIDE explicitly indicates that a virtual member function in a class + * overrides a member function of a base class, rather than potentially being a + * new member function. MOZ_OVERRIDE should be placed immediately before the + * ';' terminating the member function's declaration, or before '= 0;' if the + * member function is pure. If the member function is defined in the class + * definition, it should appear before the opening brace of the function body. + * + * class Base + * { + * public: + * virtual void f() = 0; + * }; + * class Derived1 : public Base + * { + * public: + * virtual void f() MOZ_OVERRIDE; + * }; + * class Derived2 : public Base + * { + * public: + * virtual void f() MOZ_OVERRIDE = 0; + * }; + * class Derived3 : public Base + * { + * public: + * virtual void f() MOZ_OVERRIDE { } + * }; + * + * In compilers supporting C++11 override controls, MOZ_OVERRIDE *requires* that + * the function marked with it override a member function of a base class: it + * is a compile error if it does not. Otherwise MOZ_OVERRIDE does not affect + * semantics and merely documents the override relationship to the reader (but + * of course must still be used correctly to not break C++11 compilers). + */ +#if defined(MOZ_HAVE_CXX11_OVERRIDE) +# define MOZ_OVERRIDE override +#else +# define MOZ_OVERRIDE /* no support */ +#endif + +/* + * MOZ_FINAL indicates that some functionality cannot be overridden through + * inheritance. It can be used to annotate either classes/structs or virtual + * member functions. + * + * To annotate a class/struct with MOZ_FINAL, place MOZ_FINAL immediately after + * the name of the class, before the list of classes from which it derives (if + * any) and before its opening brace. MOZ_FINAL must not be used to annotate + * unnamed classes or structs. (With some compilers, and with C++11 proper, the + * underlying expansion is ambiguous with specifying a class name.) + * + * class Base MOZ_FINAL + * { + * public: + * Base(); + * ~Base(); + * virtual void f() { } + * }; + * // This will be an error in some compilers: + * class Derived : public Base + * { + * public: + * ~Derived() { } + * }; + * + * One particularly common reason to specify MOZ_FINAL upon a class is to tell + * the compiler that it's not dangerous for it to have a non-virtual destructor + * yet have one or more virtual functions, silencing the warning it might emit + * in this case. Suppose Base above weren't annotated with MOZ_FINAL. Because + * ~Base() is non-virtual, an attempt to delete a Derived* through a Base* + * wouldn't call ~Derived(), so any cleanup ~Derived() might do wouldn't happen. + * (Formally C++ says behavior is undefined, but compilers will likely just call + * ~Base() and not ~Derived().) Specifying MOZ_FINAL tells the compiler that + * it's safe for the destructor to be non-virtual. + * + * In compilers implementing final controls, it is an error to inherit from a + * class annotated with MOZ_FINAL. In other compilers it serves only as + * documentation. + * + * To annotate a virtual member function with MOZ_FINAL, place MOZ_FINAL + * immediately before the ';' terminating the member function's declaration, or + * before '= 0;' if the member function is pure. If the member function is + * defined in the class definition, it should appear before the opening brace of + * the function body. (This placement is identical to that for MOZ_OVERRIDE. + * If both are used, they should appear in the order 'MOZ_FINAL MOZ_OVERRIDE' + * for consistency.) + * + * class Base + * { + * public: + * virtual void f() MOZ_FINAL; + * }; + * class Derived + * { + * public: + * // This will be an error in some compilers: + * virtual void f(); + * }; + * + * In compilers implementing final controls, it is an error for a derived class + * to override a method annotated with MOZ_FINAL. In other compilers it serves + * only as documentation. + */ +#if defined(MOZ_HAVE_CXX11_FINAL) +# define MOZ_FINAL MOZ_HAVE_CXX11_FINAL +#else +# define MOZ_FINAL /* no support */ +#endif + +/** + * MOZ_ENUM_TYPE specifies the underlying numeric type for an enum. It's + * specified by placing MOZ_ENUM_TYPE(type) immediately after the enum name in + * its declaration, and before the opening curly brace, like + * + * enum MyEnum MOZ_ENUM_TYPE(uint16_t) + * { + * A, + * B = 7, + * C + * }; + * + * In supporting compilers, the macro will expand to ": uint16_t". The + * compiler will allocate exactly two bytes for MyEnum, and will require all + * enumerators to have values between 0 and 65535. (Thus specifying "B = + * 100000" instead of "B = 7" would fail to compile.) In old compilers, the + * macro expands to the empty string, and the underlying type is generally + * undefined. + */ +#ifdef MOZ_HAVE_CXX11_ENUM_TYPE +# define MOZ_ENUM_TYPE(type) : type +#else +# define MOZ_ENUM_TYPE(type) /* no support */ +#endif + +/** + * MOZ_BEGIN_ENUM_CLASS and MOZ_END_ENUM_CLASS provide access to the + * strongly-typed enumeration feature of C++11 ("enum class"). If supported + * by the compiler, an enum defined using these macros will not be implicitly + * converted to any other type, and its enumerators will be scoped using the + * enumeration name. Place MOZ_BEGIN_ENUM_CLASS(EnumName, type) in place of + * "enum EnumName {", and MOZ_END_ENUM_CLASS(EnumName) in place of the closing + * "};". For example, + * + * MOZ_BEGIN_ENUM_CLASS(Enum, int32_t) + * A, B = 6 + * MOZ_END_ENUM_CLASS(Enum) + * + * This will make "Enum::A" and "Enum::B" appear in the global scope, but "A" + * and "B" will not. In compilers that support C++11 strongly-typed + * enumerations, implicit conversions of Enum values to numeric types will + * fail. In other compilers, Enum itself will actually be defined as a class, + * and some implicit conversions will fail while others will succeed. + * + * The type argument specifies the underlying type for the enum where + * supported, as with MOZ_ENUM_TYPE(). For simplicity, it is currently + * mandatory. As with MOZ_ENUM_TYPE(), it will do nothing on compilers that do + * not support it. + */ +#if defined(MOZ_HAVE_CXX11_STRONG_ENUMS) + /* All compilers that support strong enums also support an explicit + * underlying type, so no extra check is needed */ +# define MOZ_BEGIN_ENUM_CLASS(Name, type) enum class Name : type { +# define MOZ_END_ENUM_CLASS(Name) }; +#else + /** + * We need Name to both name a type, and scope the provided enumerator + * names. Namespaces and classes both provide scoping, but namespaces + * aren't types, so we need to use a class that wraps the enum values. We + * have an implicit conversion from the inner enum type to the class, so + * statements like + * + * Enum x = Enum::A; + * + * will still work. We need to define an implicit conversion from the class + * to the inner enum as well, so that (for instance) switch statements will + * work. This means that the class can be implicitly converted to a numeric + * value as well via the enum type, since C++ allows an implicit + * user-defined conversion followed by a standard conversion to still be + * implicit. + * + * We have an explicit constructor from int defined, so that casts like + * (Enum)7 will still work. We also have a zero-argument constructor with + * no arguments, so declaration without initialization (like "Enum foo;") + * will work. + * + * Additionally, we'll delete as many operators as possible for the inner + * enum type, so statements like this will still fail: + * + * f(5 + Enum::B); // deleted operator+ + * + * But we can't prevent things like this, because C++ doesn't allow + * overriding conversions or assignment operators for enums: + * + * int x = Enum::A; + * int f() + * { + * return Enum::A; + * } + */ +# define MOZ_BEGIN_ENUM_CLASS(Name, type) \ + class Name \ + { \ + public: \ + enum Enum MOZ_ENUM_TYPE(type) \ + { +# define MOZ_END_ENUM_CLASS(Name) \ + }; \ + Name() {} \ + Name(Enum aEnum) : mEnum(aEnum) {} \ + explicit Name(int num) : mEnum((Enum)num) {} \ + operator Enum() const { return mEnum; } \ + private: \ + Enum mEnum; \ + }; \ + inline int operator+(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator+(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator-(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator-(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator*(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator*(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator/(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator/(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator%(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator%(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator+(const Name::Enum&) MOZ_DELETE; \ + inline int operator-(const Name::Enum&) MOZ_DELETE; \ + inline int& operator++(Name::Enum&) MOZ_DELETE; \ + inline int operator++(Name::Enum&, int) MOZ_DELETE; \ + inline int& operator--(Name::Enum&) MOZ_DELETE; \ + inline int operator--(Name::Enum&, int) MOZ_DELETE; \ + inline bool operator==(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator==(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator!=(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator!=(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator>(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator>(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator<(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator<(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator>=(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator>=(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator<=(const int&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator<=(const Name::Enum&, const int&) MOZ_DELETE; \ + inline bool operator!(const Name::Enum&) MOZ_DELETE; \ + inline bool operator&&(const bool&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator&&(const Name::Enum&, const bool&) MOZ_DELETE; \ + inline bool operator||(const bool&, const Name::Enum&) MOZ_DELETE; \ + inline bool operator||(const Name::Enum&, const bool&) MOZ_DELETE; \ + inline int operator~(const Name::Enum&) MOZ_DELETE; \ + inline int operator&(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator&(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator|(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator|(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator^(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator^(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator<<(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator<<(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int operator>>(const int&, const Name::Enum&) MOZ_DELETE; \ + inline int operator>>(const Name::Enum&, const int&) MOZ_DELETE; \ + inline int& operator+=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator-=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator*=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator/=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator%=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator&=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator|=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator^=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator<<=(int&, const Name::Enum&) MOZ_DELETE; \ + inline int& operator>>=(int&, const Name::Enum&) MOZ_DELETE; +#endif + +/** + * MOZ_WARN_UNUSED_RESULT tells the compiler to emit a warning if a function's + * return value is not used by the caller. + * + * Place this attribute at the very beginning of a function definition. For + * example, write + * + * MOZ_WARN_UNUSED_RESULT int foo(); + * + * or + * + * MOZ_WARN_UNUSED_RESULT int foo() { return 42; } + */ +#if defined(__GNUC__) || defined(__clang__) +# define MOZ_WARN_UNUSED_RESULT __attribute__ ((warn_unused_result)) +#else +# define MOZ_WARN_UNUSED_RESULT +#endif + +#endif /* __cplusplus */ + +#endif /* mozilla_Attributes_h_ */ |