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gecko-dev/mfbt/Attributes.h

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/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* vim: set ts=8 sw=4 et tw=99 ft=cpp:
*
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at:
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Code.
*
* The Initial Developer of the Original Code is
* The Mozilla Foundation
* Portions created by the Initial Developer are Copyright (C) 2011
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Jeff Walden <jwalden+code@mit.edu> (original author)
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
/* 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_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
# 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
# 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
#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_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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