/* -*- 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 * 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 */