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gecko/mfbt/Attributes.h

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/* -*- 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.
*/
/*
* 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(PRUint16)
* {
* A,
* B = 7,
* C
* };
*
* In supporting compilers, the macro will expand to ": PRUint16". 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, PRInt32)
* 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.
*
* 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(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_ */
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