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