/* -*- 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 */ # if _MSC_VER >= 1800 # define MOZ_HAVE_CXX11_DELETE # endif # if _MSC_VER >= 1700 # define MOZ_HAVE_CXX11_FINAL final # else # if defined(__clang__) # error Please do not try to use clang-cl with MSVC10 or below emulation! # endif /* MSVC <= 10 used to spell "final" as "sealed". */ # define MOZ_HAVE_CXX11_FINAL sealed # endif # define MOZ_HAVE_CXX11_OVERRIDE # define MOZ_HAVE_NEVER_INLINE __declspec(noinline) # define MOZ_HAVE_NORETURN __declspec(noreturn) #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_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 MOZ_GCC_VERSION_AT_LEAST(4, 7, 0) # define MOZ_HAVE_CXX11_OVERRIDE # define MOZ_HAVE_CXX11_FINAL final # endif # if MOZ_GCC_VERSION_AT_LEAST(4, 6, 0) # define MOZ_HAVE_CXX11_CONSTEXPR # endif # if MOZ_GCC_VERSION_AT_LEAST(4, 5, 0) # define MOZ_HAVE_EXPLICIT_CONVERSION # endif # define MOZ_HAVE_CXX11_DELETE # else /* __final is a non-C++11 GCC synonym for 'final', per GCC r176655. */ # if MOZ_GCC_VERSION_AT_LEAST(4, 7, 0) # define MOZ_HAVE_CXX11_FINAL __final # endif # 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 #else # define MOZ_CONSTEXPR /* no support */ # define MOZ_CONSTEXPR_VAR const #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* ptr; * MOZ_EXPLICIT_CONVERSION operator bool() const { * return ptr != 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_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 #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 /* * 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 MOZ_FINAL for classes!) * * class MOZ_CLASS_ATTRIBUTE SomeClass {}; * * Attributes that apply to functions follow the parentheses and const * qualifiers but precede MOZ_FINAL, MOZ_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 MOZ_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_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. */ #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_IMPLICIT __attribute__((annotate("moz_implicit"))) /* * 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_IMPLICIT /* nothing */ # define MOZ_HEAP_ALLOCATOR /* nothing */ #endif /* MOZ_CLANG_PLUGIN */ /* * MOZ_THIS_IN_INITIALIZER_LIST is used to avoid a warning when we know that * it's safe to use 'this' in an initializer list. */ #ifdef _MSC_VER # define MOZ_THIS_IN_INITIALIZER_LIST() \ __pragma(warning(push)) \ __pragma(warning(disable:4355)) \ this \ __pragma(warning(pop)) #else # define MOZ_THIS_IN_INITIALIZER_LIST() this #endif #endif /* __cplusplus */ #endif /* mozilla_Attributes_h */