diff -r 000000000000 -r 6474c204b198 mfbt/Attributes.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mfbt/Attributes.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,492 @@ +/* -*- 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 + +/* + * 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_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)) +#elif defined(_MSC_VER) +# if _MSC_VER >= 1800 +# define MOZ_HAVE_CXX11_DELETE +# endif +# if _MSC_VER >= 1700 +# define MOZ_HAVE_CXX11_FINAL final +# else + /* 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) +// Staying away from explicit conversion operators in MSVC for now, see +// http://stackoverflow.com/questions/20498142/visual-studio-2013-explicit-keyword-bug +#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_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. + */ +#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"))) +/* + * 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_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 */