mfbt/Attributes.h
author Boris Zbarsky <bzbarsky@mit.edu>
Wed, 24 Jun 2015 00:42:46 -0700
changeset 250045 4267b74ee795e8127ffce4d45d00384cd8170130
parent 246936 229b03af6f2b7d8f598d768531cffcbd0c508552
child 252574 6f25cf87649092d52c7446369bc3dd6fb5ec5af9
permissions -rw-r--r--
Bug 1176083. Remove the now-dead code for the XPCOM version of setTimeout/setInterval. r=smaug I claim this code is dead because on the one hand it's no longer called from JS (because Window is always on WebIDL bindings, but on the other hand it can't really be called from C++ because it depends on examining the XPConnect call information. I think removing this completely, including from the IDL, is safe, because nothing directly returns nsIDOMJSWindow, so anyone using its vtable would have to QI to it and we're changing the IID.

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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

#include "mozilla/Compiler.h"

/*
 * 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 inline hint:
 * compilers are not guaranteed to respect it (although they're much more likely
 * to do so).
 *
 * The MOZ_ALWAYS_INLINE_EVEN_DEBUG macro is yet stronger. It tells the
 * compiler to inline even in DEBUG builds. It should be used very rarely.
 */
#if defined(_MSC_VER)
#  define MOZ_ALWAYS_INLINE_EVEN_DEBUG     __forceinline
#elif defined(__GNUC__)
#  define MOZ_ALWAYS_INLINE_EVEN_DEBUG     __attribute__((always_inline)) inline
#else
#  define MOZ_ALWAYS_INLINE_EVEN_DEBUG     inline
#endif

#if !defined(DEBUG)
#  define MOZ_ALWAYS_INLINE     MOZ_ALWAYS_INLINE_EVEN_DEBUG
#elif defined(_MSC_VER) && !defined(__cplusplus)
#  define MOZ_ALWAYS_INLINE     __inline
#else
#  define MOZ_ALWAYS_INLINE     inline
#endif

#if defined(_MSC_VER)
/*
 * 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.
 *
 * Even though some versions of MSVC support explicit conversion operators, we
 * don't indicate support for them here, due to
 * http://stackoverflow.com/questions/20498142/visual-studio-2013-explicit-keyword-bug
 */
#  define MOZ_HAVE_NEVER_INLINE          __declspec(noinline)
#  define MOZ_HAVE_NORETURN              __declspec(noreturn)
#  ifdef __clang__
     /* clang-cl probably supports constexpr and explicit conversions. */
#    if __has_extension(cxx_constexpr)
#      define MOZ_HAVE_CXX11_CONSTEXPR
#    endif
#    if __has_extension(cxx_explicit_conversions)
#      define MOZ_HAVE_EXPLICIT_CONVERSION
#    endif
#  endif
#elif 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_constexpr)
#    define MOZ_HAVE_CXX11_CONSTEXPR
#  endif
#  if __has_extension(cxx_explicit_conversions)
#    define MOZ_HAVE_EXPLICIT_CONVERSION
#  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
#    define MOZ_HAVE_CXX11_CONSTEXPR
#    if MOZ_GCC_VERSION_AT_LEAST(4, 8, 0)
#      define MOZ_HAVE_CXX11_CONSTEXPR_IN_TEMPLATES
#    endif
#    define MOZ_HAVE_EXPLICIT_CONVERSION
#  endif
#  define MOZ_HAVE_NEVER_INLINE          __attribute__((noinline))
#  define MOZ_HAVE_NORETURN              __attribute__((noreturn))
#endif

/*
 * When built with clang analyzer (a.k.a scan-build), define MOZ_HAVE_NORETURN
 * to mark some false positives
 */
#ifdef __clang_analyzer__
#  if __has_extension(attribute_analyzer_noreturn)
#    define MOZ_HAVE_ANALYZER_NORETURN __attribute__((analyzer_noreturn))
#  endif
#endif

/*
 * The MOZ_CONSTEXPR specifier declares that a C++11 compiler can evaluate a
 * function at compile time. A constexpr function cannot examine any values
 * except its arguments and can have no side effects except its return value.
 * The MOZ_CONSTEXPR_VAR specifier tells a C++11 compiler that a variable's
 * value may be computed at compile time.  It should be prefered to just
 * marking variables as MOZ_CONSTEXPR because if the compiler does not support
 * constexpr it will fall back to making the variable const, and some compilers
 * do not accept variables being marked both const and constexpr.
 */
#ifdef MOZ_HAVE_CXX11_CONSTEXPR
#  define MOZ_CONSTEXPR         constexpr
#  define MOZ_CONSTEXPR_VAR     constexpr
#  ifdef MOZ_HAVE_CXX11_CONSTEXPR_IN_TEMPLATES
#    define MOZ_CONSTEXPR_TMPL  constexpr
#  else
#    define MOZ_CONSTEXPR_TMPL
#  endif
#else
#  define MOZ_CONSTEXPR         /* no support */
#  define MOZ_CONSTEXPR_VAR     const
#  define MOZ_CONSTEXPR_TMPL
#endif

/*
 * MOZ_EXPLICIT_CONVERSION is a specifier on a type conversion
 * overloaded operator that declares that a C++11 compiler should restrict
 * this operator to allow only explicit type conversions, disallowing
 * implicit conversions.
 *
 * Example:
 *
 *   template<typename T>
 *   class Ptr
 *   {
 *     T* mPtr;
 *     MOZ_EXPLICIT_CONVERSION operator bool() const
 *     {
 *       return mPtr != nullptr;
 *     }
 *   };
 *
 */
#ifdef MOZ_HAVE_EXPLICIT_CONVERSION
#  define MOZ_EXPLICIT_CONVERSION explicit
#else
#  define MOZ_EXPLICIT_CONVERSION /* no support */
#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_COLD tells the compiler that a function is "cold", meaning infrequently
 * executed. This may lead it to optimize for size more aggressively than speed,
 * or to allocate the body of the function in a distant part of the text segment
 * to help keep it from taking up unnecessary icache when it isn't in use.
 *
 * Place this attribute at the very beginning of a function definition. For
 * example, write
 *
 *   MOZ_COLD int foo();
 *
 * or
 *
 *   MOZ_COLD int foo() { return 42; }
 */
#if defined(__GNUC__) || defined(__clang__)
#  define MOZ_COLD __attribute__ ((cold))
#else
#  define MOZ_COLD
#endif

/**
 * MOZ_NONNULL tells the compiler that some of the arguments to a function are
 * known to be non-null. The arguments are a list of 1-based argument indexes
 * identifying arguments which are known to be non-null.
 *
 * Place this attribute at the very beginning of a function definition. For
 * example, write
 *
 *   MOZ_NONNULL(1, 2) int foo(char *p, char *q);
 */
#if defined(__GNUC__) || defined(__clang__)
#  define MOZ_NONNULL(...) __attribute__ ((nonnull(__VA_ARGS__)))
#else
#  define MOZ_NONNULL(...)
#endif

/*
 * MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS, specified at the end of a function
 * declaration, indicates that for the purposes of static analysis, this
 * function does not return.  (The function definition does not need to be
 * annotated.)
 *
 * MOZ_ReportCrash(const char* s, const char* file, int ln)
 *   MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
 *
 * Some static analyzers, like scan-build from clang, can use this information
 * to eliminate false positives.  From the upstream documentation of scan-build:
 * "This attribute is useful for annotating assertion handlers that actually
 * can return, but for the purpose of using the analyzer we want to pretend
 * that such functions do not return."
 *
 */
#if defined(MOZ_HAVE_ANALYZER_NORETURN)
#  define MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS          MOZ_HAVE_ANALYZER_NORETURN
#else
#  define MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS          /* no support */
#endif

/*
 * MOZ_ASAN_BLACKLIST is a macro to tell AddressSanitizer (a compile-time
 * instrumentation shipped with Clang and GCC) 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(__has_feature)
#  if __has_feature(address_sanitizer)
#    define MOZ_HAVE_ASAN_BLACKLIST
#  endif
#elif defined(__GNUC__)
#  if defined(__SANITIZE_ADDRESS__)
#    define MOZ_HAVE_ASAN_BLACKLIST
#  endif
#endif

#if defined(MOZ_HAVE_ASAN_BLACKLIST)
#  define MOZ_ASAN_BLACKLIST MOZ_NEVER_INLINE __attribute__((no_sanitize_address))
#else
#  define MOZ_ASAN_BLACKLIST /* nothing */
#endif

/*
 * MOZ_TSAN_BLACKLIST is a macro to tell ThreadSanitizer (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 ThreadSanitizer.
 */
#if defined(__has_feature)
#  if __has_feature(thread_sanitizer)
#    define MOZ_TSAN_BLACKLIST MOZ_NEVER_INLINE __attribute__((no_sanitize_thread))
#  else
#    define MOZ_TSAN_BLACKLIST /* nothing */
#  endif
#else
#  define MOZ_TSAN_BLACKLIST /* nothing */
#endif

/**
 * MOZ_ALLOCATOR tells the compiler that the function it marks returns either a
 * "fresh", "pointer-free" block of memory, or nullptr. "Fresh" means that the
 * block is not pointed to by any other reachable pointer in the program.
 * "Pointer-free" means that the block contains no pointers to any valid object
 * in the program. It may be initialized with other (non-pointer) values.
 *
 * Placing this attribute on appropriate functions helps GCC analyze pointer
 * aliasing more accurately in their callers.
 *
 * GCC warns if a caller ignores the value returned by a function marked with
 * MOZ_ALLOCATOR: it is hard to imagine cases where dropping the value returned
 * by a function that meets the criteria above would be intentional.
 *
 * Place this attribute after the argument list and 'this' qualifiers of a
 * function definition. For example, write
 *
 *   void *my_allocator(size_t) MOZ_ALLOCATOR;
 *
 * or
 *
 *   void *my_allocator(size_t bytes) MOZ_ALLOCATOR { ... }
 */
#if defined(__GNUC__) || defined(__clang__)
#  define MOZ_ALLOCATOR __attribute__ ((malloc, warn_unused_result))
#else
#  define MOZ_ALLOCATOR
#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

#ifdef __cplusplus

/*
 * The following macros are attributes that support the static analysis plugin
 * included with Mozilla, and will be implemented (when such support is enabled)
 * as C++11 attributes. Since such attributes are legal pretty much everywhere
 * and have subtly different semantics depending on their placement, the
 * following is a guide on where to place the attributes.
 *
 * Attributes that apply to a struct or class precede the name of the class:
 * (Note that this is different from the placement of final for classes!)
 *
 *   class MOZ_CLASS_ATTRIBUTE SomeClass {};
 *
 * Attributes that apply to functions follow the parentheses and const
 * qualifiers but precede final, override and the function body:
 *
 *   void DeclaredFunction() MOZ_FUNCTION_ATTRIBUTE;
 *   void SomeFunction() MOZ_FUNCTION_ATTRIBUTE {}
 *   void PureFunction() const MOZ_FUNCTION_ATTRIBUTE = 0;
 *   void OverriddenFunction() MOZ_FUNCTION_ATTIRBUTE override;
 *
 * Attributes that apply to variables or parameters follow the variable's name:
 *
 *   int variable MOZ_VARIABLE_ATTRIBUTE;
 *
 * Attributes that apply to types follow the type name:
 *
 *   typedef int MOZ_TYPE_ATTRIBUTE MagicInt;
 *   int MOZ_TYPE_ATTRIBUTE someVariable;
 *   int* MOZ_TYPE_ATTRIBUTE magicPtrInt;
 *   int MOZ_TYPE_ATTRIBUTE* ptrToMagicInt;
 *
 * Attributes that apply to statements precede the statement:
 *
 *   MOZ_IF_ATTRIBUTE if (x == 0)
 *   MOZ_DO_ATTRIBUTE do { } while (0);
 *
 * Attributes that apply to labels precede the label:
 *
 *   MOZ_LABEL_ATTRIBUTE target:
 *     goto target;
 *   MOZ_CASE_ATTRIBUTE case 5:
 *   MOZ_DEFAULT_ATTRIBUTE default:
 *
 * The static analyses that are performed by the plugin are as follows:
 *
 * MOZ_MUST_OVERRIDE: Applies to all C++ member functions. All immediate
 *   subclasses must provide an exact override of this method; if a subclass
 *   does not override this method, the compiler will emit an error. This
 *   attribute is not limited to virtual methods, so if it is applied to a
 *   nonvirtual method and the subclass does not provide an equivalent
 *   definition, the compiler will emit an error.
 * MOZ_STACK_CLASS: Applies to all classes. Any class with this annotation is
 *   expected to live on the stack, so it is a compile-time error to use it, or
 *   an array of such objects, as a global or static variable, or as the type of
 *   a new expression (unless placement new is being used). If a member of
 *   another class uses this class, or if another class inherits from this
 *   class, then it is considered to be a stack class as well, although this
 *   attribute need not be provided in such cases.
 * MOZ_NONHEAP_CLASS: Applies to all classes. Any class with this annotation is
 *   expected to live on the stack or in static storage, so it is a compile-time
 *   error to use it, or an array of such objects, as the type of a new
 *   expression (unless placement new is being used). If a member of another
 *   class uses this class, or if another class inherits from this class, then
 *   it is considered to be a non-heap class as well, although this attribute
 *   need not be provided in such cases.
 * MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS: Applies to all classes that are
 *   intended to prevent introducing static initializers.  This attribute
 *   currently makes it a compile-time error to instantiate these classes
 *   anywhere other than at the global scope, or as a static member of a class.
 * MOZ_TRIVIAL_CTOR_DTOR: Applies to all classes that must have both a trivial
 *   constructor and a trivial destructor.  Setting this attribute on a class
 *   makes it a compile-time error for that class to get a non-trivial
 *   constructor or destructor for any reason.
 * MOZ_HEAP_ALLOCATOR: Applies to any function. This indicates that the return
 *   value is allocated on the heap, and will as a result check such allocations
 *   during MOZ_STACK_CLASS and MOZ_NONHEAP_CLASS annotation checking.
 * MOZ_IMPLICIT: Applies to constructors. Implicit conversion constructors
 *   are disallowed by default unless they are marked as MOZ_IMPLICIT. This
 *   attribute must be used for constructors which intend to provide implicit
 *   conversions.
 * MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT: Applies to functions. Makes it a compile
 *   time error to pass arithmetic expressions on variables to the function.
 * MOZ_OWNING_REF: Applies to declarations of pointers to reference counted
 *   types.  This attribute tells the compiler that the raw pointer is a strong
 *   reference, where ownership through methods such as AddRef and Release is
 *   managed manually.  This can make the compiler ignore these pointers when
 *   validating the usage of pointers otherwise.
 *
 *   Example uses include owned pointers inside of unions, and pointers stored
 *   in POD types where a using a smart pointer class would make the object
 *   non-POD.
 * MOZ_NON_OWNING_REF: Applies to declarations of pointers to reference counted
 *   types.  This attribute tells the compiler that the raw pointer is a weak
 *   reference, which is ensured to be valid by a guarantee that the reference
 *   will be nulled before the pointer becomes invalid.  This can make the compiler
 *   ignore these pointers when validating the usage of pointers otherwise.
 *
 *   Examples include an mOwner pointer, which is nulled by the owning class's
 *   destructor, and is null-checked before dereferencing.
 * MOZ_UNSAFE_REF: Applies to declarations of pointers to reference counted types.
 *   Occasionally there are non-owning references which are valid, but do not take
 *   the form of a MOZ_NON_OWNING_REF.  Their safety may be dependent on the behaviour
 *   of API consumers.  The string argument passed to this macro documents the safety
 *   conditions.  This can make the compiler ignore these pointers when validating
 *   the usage of pointers elsewhere.
 *
 *   Examples include an nsIAtom* member which is known at compile time to point to a
 *   static atom which is valid throughout the lifetime of the program, or an API which
 *   stores a pointer, but doesn't take ownership over it, instead requiring the API
 *   consumer to correctly null the value before it becomes invalid.
 *
 *   Use of this annotation is discouraged when a strong reference or one of the above
 *   two annotations can be used instead.
 * MOZ_NO_ADDREF_RELEASE_ON_RETURN: Applies to function declarations.  Makes it
 *   a compile time error to call AddRef or Release on the return value of a
 *   function.  This is intended to be used with operator->() of our smart
 *   pointer classes to ensure that the refcount of an object wrapped in a
 *   smart pointer is not manipulated directly.
 */
#ifdef MOZ_CLANG_PLUGIN
#  define MOZ_MUST_OVERRIDE __attribute__((annotate("moz_must_override")))
#  define MOZ_STACK_CLASS __attribute__((annotate("moz_stack_class")))
#  define MOZ_NONHEAP_CLASS __attribute__((annotate("moz_nonheap_class")))
#  define MOZ_TRIVIAL_CTOR_DTOR __attribute__((annotate("moz_trivial_ctor_dtor")))
#  ifdef DEBUG
     /* in debug builds, these classes do have non-trivial constructors. */
#    define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS __attribute__((annotate("moz_global_class")))
#  else
#    define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS __attribute__((annotate("moz_global_class"))) \
            MOZ_TRIVIAL_CTOR_DTOR
#  endif
#  define MOZ_IMPLICIT __attribute__((annotate("moz_implicit")))
#  define MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT __attribute__((annotate("moz_no_arith_expr_in_arg")))
#  define MOZ_OWNING_REF __attribute__((annotate("moz_strong_ref")))
#  define MOZ_NON_OWNING_REF __attribute__((annotate("moz_weak_ref")))
#  define MOZ_UNSAFE_REF(reason) __attribute__((annotate("moz_weak_ref")))
#  define MOZ_NO_ADDREF_RELEASE_ON_RETURN __attribute__((annotate("moz_no_addref_release_on_return")))
/*
 * It turns out that clang doesn't like void func() __attribute__ {} without a
 * warning, so use pragmas to disable the warning. This code won't work on GCC
 * anyways, so the warning is safe to ignore.
 */
#  define MOZ_HEAP_ALLOCATOR \
    _Pragma("clang diagnostic push") \
    _Pragma("clang diagnostic ignored \"-Wgcc-compat\"") \
    __attribute__((annotate("moz_heap_allocator"))) \
    _Pragma("clang diagnostic pop")
#else
#  define MOZ_MUST_OVERRIDE /* nothing */
#  define MOZ_STACK_CLASS /* nothing */
#  define MOZ_NONHEAP_CLASS /* nothing */
#  define MOZ_TRIVIAL_CTOR_DTOR /* nothing */
#  define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS /* nothing */
#  define MOZ_IMPLICIT /* nothing */
#  define MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT /* nothing */
#  define MOZ_HEAP_ALLOCATOR /* nothing */
#  define MOZ_OWNING_REF /* nothing */
#  define MOZ_NON_OWNING_REF /* nothing */
#  define MOZ_UNSAFE_REF(reason) /* nothing */
#  define MOZ_NO_ADDREF_RELEASE_ON_RETURN /* nothing */
#endif /* MOZ_CLANG_PLUGIN */

#endif /* __cplusplus */

#endif /* mozilla_Attributes_h */