/* -*- 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. */ # 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_attribute(noinline) # define MOZ_HAVE_NEVER_INLINE __attribute__((noinline)) # endif # if __has_attribute(noreturn) # define MOZ_HAVE_NORETURN __attribute__((noreturn)) # endif #elif defined(__GNUC__) # define MOZ_HAVE_NEVER_INLINE __attribute__((noinline)) # define MOZ_HAVE_NORETURN __attribute__((noreturn)) # define MOZ_HAVE_NORETURN_PTR __attribute__((noreturn)) #endif #if defined(__clang__) # if __has_attribute(no_stack_protector) # define MOZ_HAVE_NO_STACK_PROTECTOR __attribute__((no_stack_protector)) # endif #elif defined(__GNUC__) # define MOZ_HAVE_NO_STACK_PROTECTOR __attribute__((no_stack_protector)) #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 #if defined(__GNUC__) || \ (defined(__clang__) && __has_attribute(no_profile_instrument_function)) # define MOZ_NOPROFILE __attribute__((no_profile_instrument_function)) #else # define MOZ_NOPROFILE #endif #if defined(__GNUC__) || \ (defined(__clang__) && __has_attribute(no_instrument_function)) # define MOZ_NOINSTRUMENT __attribute__((no_instrument_function)) #else # define MOZ_NOINSTRUMENT #endif /* * MOZ_NAKED tells the compiler that the function only contains assembly and * that it should not try to inject code that may mess with the assembly in it. * * See https://github.com/llvm/llvm-project/issues/74573 for the interaction * between naked and no_profile_instrument_function. */ #define MOZ_NAKED __attribute__((naked)) MOZ_NOPROFILE MOZ_NOINSTRUMENT /** * Per clang's documentation: * * If a statement is marked nomerge and contains call expressions, those call * expressions inside the statement will not be merged during optimization. This * attribute can be used to prevent the optimizer from obscuring the source * location of certain calls. * * This is useful to have clearer information on assertion failures. */ #if defined(__clang__) && __has_attribute(nomerge) # define MOZ_NOMERGE __attribute__((nomerge)) #else # define MOZ_NOMERGE #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_NEVER_INLINE_DEBUG is a macro which expands to MOZ_NEVER_INLINE * in debug builds, and nothing in opt builds. */ #if defined(DEBUG) # define MOZ_NEVER_INLINE_DEBUG MOZ_NEVER_INLINE #else # define MOZ_NEVER_INLINE_DEBUG /* don't inline in opt builds */ #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. * * There are two variants. The GCC version of NORETURN may be applied to a * function pointer, while for MSVC it may not. * * 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 #if defined(MOZ_HAVE_NORETURN_PTR) # define MOZ_NORETURN_PTR MOZ_HAVE_NORETURN_PTR #else # define MOZ_NORETURN_PTR /* 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_NONNULL_RETURN tells the compiler that the function's return value is * guaranteed to be a non-null pointer, which may enable the compiler to * optimize better at call sites. * * Place this attribute at the end of a function declaration. For example, * * char* foo(char *p, char *q) MOZ_NONNULL_RETURN; */ #if defined(__GNUC__) || defined(__clang__) # define MOZ_NONNULL_RETURN __attribute__((returns_nonnull)) #else # define MOZ_NONNULL_RETURN #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_IGNORE 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 blocklisting mechanism of * AddressSanitizer. */ #if defined(__has_feature) # if __has_feature(address_sanitizer) # define MOZ_HAVE_ASAN_IGNORE # endif #elif defined(__GNUC__) # if defined(__SANITIZE_ADDRESS__) # define MOZ_HAVE_ASAN_IGNORE # endif #endif #if defined(MOZ_HAVE_ASAN_IGNORE) # define MOZ_ASAN_IGNORE MOZ_NEVER_INLINE __attribute__((no_sanitize_address)) #else # define MOZ_ASAN_IGNORE /* nothing */ #endif /* * MOZ_TSAN_IGNORE 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 blocklisting mechanism of ThreadSanitizer. */ #if defined(__has_feature) # if __has_feature(thread_sanitizer) # define MOZ_TSAN_IGNORE MOZ_NEVER_INLINE __attribute__((no_sanitize_thread)) # else # define MOZ_TSAN_IGNORE /* nothing */ # endif #else # define MOZ_TSAN_IGNORE /* nothing */ #endif #if defined(__has_attribute) # if __has_attribute(no_sanitize) # define MOZ_HAVE_NO_SANITIZE_ATTR # endif #endif #ifdef __clang__ # ifdef MOZ_HAVE_NO_SANITIZE_ATTR # define MOZ_HAVE_UNSIGNED_OVERFLOW_SANITIZE_ATTR # define MOZ_HAVE_SIGNED_OVERFLOW_SANITIZE_ATTR # endif #endif /* * MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW disables *un*signed integer overflow * checking on the function it annotates, in builds configured to perform it. * (Currently this is only Clang using -fsanitize=unsigned-integer-overflow, or * via --enable-unsigned-overflow-sanitizer in Mozilla's build system.) It has * no effect in other builds. * * Place this attribute at the very beginning of a function declaration. * * Unsigned integer overflow isn't *necessarily* a bug. It's well-defined in * C/C++, and code may reasonably depend upon it. For example, * * MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW inline bool * IsDecimal(char aChar) * { * // For chars less than '0', unsigned integer underflow occurs, to a value * // much greater than 10, so the overall test is false. * // For chars greater than '0', no overflow occurs, and only '0' to '9' * // pass the overall test. * return static_cast(aChar) - '0' < 10; * } * * But even well-defined unsigned overflow often causes bugs when it occurs, so * it should be restricted to functions annotated with this attribute. * * The compiler instrumentation to detect unsigned integer overflow has costs * both at compile time and at runtime. Functions that are repeatedly inlined * at compile time will also implicitly inline the necessary instrumentation, * increasing compile time. Similarly, frequently-executed functions that * require large amounts of instrumentation will also notice significant runtime * slowdown to execute that instrumentation. Use this attribute to eliminate * those costs -- but only after carefully verifying that no overflow can occur. */ #ifdef MOZ_HAVE_UNSIGNED_OVERFLOW_SANITIZE_ATTR # define MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW \ __attribute__((no_sanitize("unsigned-integer-overflow"))) #else # define MOZ_NO_SANITIZE_UNSIGNED_OVERFLOW /* nothing */ #endif /* * MOZ_NO_SANITIZE_SIGNED_OVERFLOW disables *signed* integer overflow checking * on the function it annotates, in builds configured to perform it. (Currently * this is only Clang using -fsanitize=signed-integer-overflow, or via * --enable-signed-overflow-sanitizer in Mozilla's build system. GCC support * will probably be added in the future.) It has no effect in other builds. * * Place this attribute at the very beginning of a function declaration. * * Signed integer overflow is undefined behavior in C/C++: *anything* can happen * when it occurs. *Maybe* wraparound behavior will occur, but maybe also the * compiler will assume no overflow happens and will adversely optimize the rest * of your code. Code that contains signed integer overflow needs to be fixed. * * The compiler instrumentation to detect signed integer overflow has costs both * at compile time and at runtime. Functions that are repeatedly inlined at * compile time will also implicitly inline the necessary instrumentation, * increasing compile time. Similarly, frequently-executed functions that * require large amounts of instrumentation will also notice significant runtime * slowdown to execute that instrumentation. Use this attribute to eliminate * those costs -- but only after carefully verifying that no overflow can occur. */ #ifdef MOZ_HAVE_SIGNED_OVERFLOW_SANITIZE_ATTR # define MOZ_NO_SANITIZE_SIGNED_OVERFLOW \ __attribute__((no_sanitize("signed-integer-overflow"))) #else # define MOZ_NO_SANITIZE_SIGNED_OVERFLOW /* nothing */ #endif #undef MOZ_HAVE_NO_SANITIZE_ATTR /** * 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)) # define MOZ_INFALLIBLE_ALLOCATOR \ __attribute__((malloc, warn_unused_result, returns_nonnull)) #else # define MOZ_ALLOCATOR # define MOZ_INFALLIBLE_ALLOCATOR #endif /** * MOZ_MAYBE_UNUSED suppresses compiler warnings about functions that are * never called (in this build configuration, at least). * * Place this attribute at the very beginning of a function declaration. For * example, write * * MOZ_MAYBE_UNUSED int foo(); * * or * * MOZ_MAYBE_UNUSED int foo() { return 42; } */ #if defined(__GNUC__) || defined(__clang__) # define MOZ_MAYBE_UNUSED __attribute__((__unused__)) #elif defined(_MSC_VER) # define MOZ_MAYBE_UNUSED __pragma(warning(suppress : 4505)) #else # define MOZ_MAYBE_UNUSED #endif /* * MOZ_NO_STACK_PROTECTOR, specified at the start of a function declaration, * indicates that the given function should *NOT* be instrumented to detect * stack buffer overflows at runtime. (The function definition does not need to * be annotated.) * * MOZ_NO_STACK_PROTECTOR int foo(); * * Detecting stack buffer overflows at runtime is a security feature. This * modifier should thus only be used on functions which are provably exempt of * stack buffer overflows, for example because they do not use stack buffers. * * This modifier does not affect the corresponding function's linking behavior. */ #if defined(MOZ_HAVE_NO_STACK_PROTECTOR) # define MOZ_NO_STACK_PROTECTOR MOZ_HAVE_NO_STACK_PROTECTOR #else # define MOZ_NO_STACK_PROTECTOR /* no support */ #endif /** * MOZ_LIFETIME_BOUND indicates that objects that are referred to by that * parameter may also be referred to by the return value of the annotated * function (or, for a parameter of a constructor, by the value of the * constructed object). * See: https://clang.llvm.org/docs/AttributeReference.html#lifetimebound */ #if defined(__clang__) && defined(__has_cpp_attribute) # if __has_cpp_attribute(clang::lifetimebound) # define MOZ_LIFETIME_BOUND [[clang::lifetimebound]] # else # define MOZ_LIFETIME_BOUND /* nothing */ # endif #else # define MOZ_LIFETIME_BOUND /* nothing */ #endif #ifdef __cplusplus /** * C++11 lets unions contain members that have non-trivial special member * functions (default/copy/move constructor, copy/move assignment operator, * destructor) if the user defines the corresponding functions on the union. * (Such user-defined functions must rely on external knowledge about which arm * is active to be safe. Be extra-careful defining these functions!) * * MSVC unfortunately warns/errors for this bog-standard C++11 pattern. Use * these macro-guards around such member functions to disable the warnings: * * union U * { * std::string s; * int x; * * MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS * * // |U| must have a user-defined default constructor because |std::string| * // has a non-trivial default constructor. * U() ... { ... } * * // |U| must have a user-defined destructor because |std::string| has a * // non-trivial destructor. * ~U() { ... } * * MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS * }; */ # if defined(_MSC_VER) # define MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS \ __pragma(warning(push)) __pragma(warning(disable : 4582)) \ __pragma(warning(disable : 4583)) # define MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS __pragma(warning(pop)) # else # define MOZ_PUSH_DISABLE_NONTRIVIAL_UNION_WARNINGS /* nothing */ # define MOZ_POP_DISABLE_NONTRIVIAL_UNION_WARNINGS /* nothing */ # 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 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_CAN_RUN_SCRIPT: Applies to functions which can run script. Callers of * this function must also be marked as MOZ_CAN_RUN_SCRIPT, and all refcounted * arguments must be strongly held in the caller. Note that MOZ_CAN_RUN_SCRIPT * should only be applied to function declarations, not definitions. If you * need to apply it to a definition (eg because both are generated by a macro) * use MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION. * * MOZ_CAN_RUN_SCRIPT can be applied to XPIDL-generated declarations by * annotating the method or attribute as [can_run_script] in the .idl file. * * MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION: Same as MOZ_CAN_RUN_SCRIPT, but usable on * a definition. If the declaration is in a header file, users of that header * file may not see the annotation. * MOZ_CAN_RUN_SCRIPT_BOUNDARY: Applies to functions which need to call * MOZ_CAN_RUN_SCRIPT functions, but should not themselves be considered * MOZ_CAN_RUN_SCRIPT. This should generally be avoided but can be used in * two cases: * 1) As a temporary measure to limit the scope of changes when adding * MOZ_CAN_RUN_SCRIPT. Such a use must be accompanied by a follow-up bug * to replace the MOZ_CAN_RUN_SCRIPT_BOUNDARY with MOZ_CAN_RUN_SCRIPT and * a comment linking to that bug. * 2) If we can reason that the MOZ_CAN_RUN_SCRIPT callees of the function * do not in fact run script (for example, because their behavior depends * on arguments and we pass the arguments that don't allow script * execution). Such a use must be accompanied by a comment that explains * why it's OK to have the MOZ_CAN_RUN_SCRIPT_BOUNDARY, as well as * comments in the callee pointing out that if its behavior changes the * caller might need adjusting. And perhaps also a followup bug to * refactor things so the "script" and "no script" codepaths do not share * a chokepoint. * Importantly, any use MUST be accompanied by a comment explaining why it's * there, and should ideally have an action plan for getting rid of the * MOZ_CAN_RUN_SCRIPT_BOUNDARY annotation. * 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_STATIC_CLASS: Applies to all classes. Any class with this annotation is * expected to live in static memory, so it is a compile-time error to use * it, or an array of such objects, as the type of a variable declaration, or * as a temporary object, 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 static class as well, although this attribute need not be provided * in such cases. * MOZ_STATIC_LOCAL_CLASS: Applies to all classes. Any class with this * annotation is expected to be a static local variable, so it is * a compile-time error to use it, or an array of such objects, or as a * temporary object, or as the type of a new expression. If another class * inherits from this class then it is considered to be a static local * class as well, although this attribute need not be provided in such cases. * It is also a compile-time error for any class with this annotation to have * a non-trivial destructor. * 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. 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_CLASS: Applies to all classes. Any class with this annotation is * expected to live on the heap, so it is a compile-time error to use it, or * an array of such objects, as the type of a variable declaration, or as a * temporary object. If a member of another class uses this class, or if * another class inherits from this class, then it is considered to be a heap * class as well, although this attribute need not be provided in such cases. * MOZ_NON_TEMPORARY_CLASS: Applies to all classes. Any class with this * annotation is expected not to live in a temporary. 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-temporary class as well, although this attribute * need not be provided in such cases. * MOZ_TEMPORARY_CLASS: Applies to all classes. Any class with this annotation * is expected to only live in a temporary. If another class inherits from * this class, then it is considered to be a temporary class as well, although * this attribute need not be provided in such cases. * MOZ_RAII: Applies to all classes. Any class with this annotation is assumed * to be a RAII guard, which is expected to live on the stack in an automatic * allocation. It is prohibited from being allocated in a temporary, static * storage, or on the heap. This is a combination of MOZ_STACK_CLASS and * MOZ_NON_TEMPORARY_CLASS. * 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. * In non-debug mode, it also prohibits non-trivial constructors and * destructors. * MOZ_TRIVIAL_CTOR_DTOR: Applies to all classes that must have both a trivial * or constexpr 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_ALLOW_TEMPORARY: Applies to constructors. This indicates that using the * constructor is allowed in temporary expressions, if it would have otherwise * been forbidden by the type being a MOZ_NON_TEMPORARY_CLASS. Useful for * constructors like Maybe(Nothing). * 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_IS_REFPTR: Applies to class declarations of ref pointer to mark them as * such for use with static-analysis. * A ref pointer is an object wrapping a pointer and automatically taking care * of its refcounting upon construction/destruction/transfer of ownership. * This annotation implies MOZ_IS_SMARTPTR_TO_REFCOUNTED. * MOZ_IS_SMARTPTR_TO_REFCOUNTED: Applies to class declarations of smart * pointers to ref counted classes to mark them as such for use with * static-analysis. * 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 nsAtom* 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. * MOZ_NEEDS_NO_VTABLE_TYPE: Applies to template class declarations. Makes it * a compile time error to instantiate this template with a type parameter * which has a VTable. * MOZ_NON_MEMMOVABLE: Applies to class declarations for types that are not safe * to be moved in memory using memmove(). * MOZ_NEEDS_MEMMOVABLE_TYPE: Applies to template class declarations where the * template arguments are required to be safe to move in memory using * memmove(). Passing MOZ_NON_MEMMOVABLE types to these templates is a * compile time error. * MOZ_NEEDS_MEMMOVABLE_MEMBERS: Applies to class declarations where each member * must be safe to move in memory using memmove(). MOZ_NON_MEMMOVABLE types * used in members of these classes are compile time errors. * MOZ_NO_DANGLING_ON_TEMPORARIES: Applies to method declarations which return * a pointer that is freed when the destructor of the class is called. This * prevents these methods from being called on temporaries of the class, * reducing risks of use-after-free. * This attribute cannot be applied to && methods. * In some cases, adding a deleted &&-qualified overload is too restrictive as * this method should still be callable as a non-escaping argument to another * function. This annotation can be used in those cases. * MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS: Applies to template class * declarations where an instance of the template should be considered, for * static analysis purposes, to inherit any type annotations (such as * MOZ_STACK_CLASS) from its template arguments. * MOZ_INIT_OUTSIDE_CTOR: Applies to class member declarations. Occasionally * there are class members that are not initialized in the constructor, * but logic elsewhere in the class ensures they are initialized prior to use. * Using this attribute on a member disables the check that this member must * be initialized in constructors via list-initialization, in the constructor * body, or via functions called from the constructor body. * MOZ_IS_CLASS_INIT: Applies to class method declarations. Occasionally the * constructor doesn't initialize all of the member variables and another * function is used to initialize the rest. This marker is used to make the * static analysis tool aware that the marked function is part of the * initialization process and to include the marked function in the scan * mechanism that determines which member variables still remain * uninitialized. * MOZ_NON_PARAM: Applies to types. Makes it compile time error to use the type * in parameter without pointer or reference. * MOZ_NON_AUTOABLE: Applies to class declarations. Makes it a compile time * error to use `auto` in place of this type in variable declarations. This * is intended to be used with types which are intended to be implicitly * constructed into other other types before being assigned to variables. * MOZ_REQUIRED_BASE_METHOD: Applies to virtual class method declarations. * Sometimes derived classes override methods that need to be called by their * overridden counterparts. This marker indicates that the marked method must * be called by the method that it overrides. * MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG: Applies to method declarations. * Callers of the annotated method must return from that function within the * calling block using an explicit `return` statement if the "this" value for * the call is a parameter of the caller. Only calls to Constructors, * references to local and member variables, and calls to functions or * methods marked as MOZ_MAY_CALL_AFTER_MUST_RETURN may be made after the * MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG call. * MOZ_MAY_CALL_AFTER_MUST_RETURN: Applies to function or method declarations. * Calls to these methods may be made in functions after calls a * MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG method. * MOZ_UNANNOTATED/MOZ_ANNOTATED: Applies to Mutexes/Monitors and variations on * them. MOZ_UNANNOTATED indicates that the Mutex/Monitor/etc hasn't been * examined and annotated using macros from mfbt/ThreadSafety -- * MOZ_GUARDED_BY()/REQUIRES()/etc. MOZ_ANNOTATED is used in rare cases to * indicate that is has been looked at, but it did not need any * MOZ_GUARDED_BY()/REQUIRES()/etc (and thus static analysis knows it can * ignore this Mutex/Monitor/etc) */ // gcc emits a nuisance warning -Wignored-attributes because attributes do not // affect mangled names, and therefore template arguments do not propagate // their attributes. It is rare that this would affect anything in practice, // and most compilers are silent about it. Similarly, -Wattributes complains // about attributes being ignored during template instantiation. // // Be conservative and only suppress the warning when running in a // configuration where it would be emitted, namely when compiling with the // XGILL_PLUGIN for the rooting hazard analysis (which runs under gcc.) If we // end up wanting these attributes in general GCC builds, change this to // something like // // #if defined(__GNUC__) && ! defined(__clang__) // # ifdef XGILL_PLUGIN # pragma GCC diagnostic ignored "-Wignored-attributes" # pragma GCC diagnostic ignored "-Wattributes" # endif # if defined(MOZ_CLANG_PLUGIN) || defined(XGILL_PLUGIN) # define MOZ_CAN_RUN_SCRIPT __attribute__((annotate("moz_can_run_script"))) # define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION \ __attribute__((annotate("moz_can_run_script"))) \ __attribute__((annotate("moz_can_run_script_for_definition"))) # define MOZ_CAN_RUN_SCRIPT_BOUNDARY \ __attribute__((annotate("moz_can_run_script_boundary"))) # define MOZ_MUST_OVERRIDE __attribute__((annotate("moz_must_override"))) # define MOZ_STATIC_CLASS __attribute__((annotate("moz_global_class"))) # define MOZ_STATIC_LOCAL_CLASS \ __attribute__((annotate("moz_static_local_class"))) \ __attribute__((annotate("moz_trivial_dtor"))) # define MOZ_STACK_CLASS __attribute__((annotate("moz_stack_class"))) # define MOZ_NONHEAP_CLASS __attribute__((annotate("moz_nonheap_class"))) # define MOZ_HEAP_CLASS __attribute__((annotate("moz_heap_class"))) # define MOZ_NON_TEMPORARY_CLASS \ __attribute__((annotate("moz_non_temporary_class"))) # define MOZ_TEMPORARY_CLASS __attribute__((annotate("moz_temporary_class"))) # define MOZ_TRIVIAL_CTOR_DTOR \ __attribute__((annotate("moz_trivial_ctor_dtor"))) # define MOZ_ALLOW_TEMPORARY __attribute__((annotate("moz_allow_temporary"))) # 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_IS_SMARTPTR_TO_REFCOUNTED \ __attribute__((annotate("moz_is_smartptr_to_refcounted"))) # define MOZ_IS_REFPTR MOZ_IS_SMARTPTR_TO_REFCOUNTED # define MOZ_NO_ARITHMETIC_EXPR_IN_ARGUMENT \ __attribute__((annotate("moz_no_arith_expr_in_arg"))) # define MOZ_OWNING_REF __attribute__((annotate("moz_owning_ref"))) # define MOZ_NON_OWNING_REF __attribute__((annotate("moz_non_owning_ref"))) # define MOZ_UNSAFE_REF(reason) __attribute__((annotate("moz_unsafe_ref"))) # define MOZ_NO_ADDREF_RELEASE_ON_RETURN \ __attribute__((annotate("moz_no_addref_release_on_return"))) # define MOZ_NEEDS_NO_VTABLE_TYPE \ __attribute__((annotate("moz_needs_no_vtable_type"))) # define MOZ_NON_MEMMOVABLE __attribute__((annotate("moz_non_memmovable"))) # define MOZ_NEEDS_MEMMOVABLE_TYPE \ __attribute__((annotate("moz_needs_memmovable_type"))) # define MOZ_NEEDS_MEMMOVABLE_MEMBERS \ __attribute__((annotate("moz_needs_memmovable_members"))) # define MOZ_NO_DANGLING_ON_TEMPORARIES \ __attribute__((annotate("moz_no_dangling_on_temporaries"))) # define MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS \ __attribute__(( \ annotate("moz_inherit_type_annotations_from_template_args"))) # define MOZ_NON_AUTOABLE __attribute__((annotate("moz_non_autoable"))) # define MOZ_INIT_OUTSIDE_CTOR # define MOZ_IS_CLASS_INIT # define MOZ_NON_PARAM __attribute__((annotate("moz_non_param"))) # define MOZ_REQUIRED_BASE_METHOD \ __attribute__((annotate("moz_required_base_method"))) # define MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG \ __attribute__((annotate("moz_must_return_from_caller_if_this_is_arg"))) # define MOZ_MAY_CALL_AFTER_MUST_RETURN \ __attribute__((annotate("moz_may_call_after_must_return"))) # define MOZ_KNOWN_LIVE __attribute__((annotate("moz_known_live"))) # ifndef XGILL_PLUGIN # define MOZ_UNANNOTATED __attribute__((annotate("moz_unannotated"))) # define MOZ_ANNOTATED __attribute__((annotate("moz_annotated"))) # else # define MOZ_UNANNOTATED /* nothing */ # define MOZ_ANNOTATED /* nothing */ # endif /* * It turns out that clang doesn't like void func() __attribute__ {} without a * warning, so use pragmas to disable the warning. */ # ifdef __clang__ # 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_HEAP_ALLOCATOR __attribute__((annotate("moz_heap_allocator"))) # endif # else # define MOZ_CAN_RUN_SCRIPT /* nothing */ # define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION /* nothing */ # define MOZ_CAN_RUN_SCRIPT_BOUNDARY /* nothing */ # define MOZ_MUST_OVERRIDE /* nothing */ # define MOZ_STATIC_CLASS /* nothing */ # define MOZ_STATIC_LOCAL_CLASS /* nothing */ # define MOZ_STACK_CLASS /* nothing */ # define MOZ_NONHEAP_CLASS /* nothing */ # define MOZ_HEAP_CLASS /* nothing */ # define MOZ_NON_TEMPORARY_CLASS /* nothing */ # define MOZ_TEMPORARY_CLASS /* nothing */ # define MOZ_TRIVIAL_CTOR_DTOR /* nothing */ # define MOZ_ALLOW_TEMPORARY /* nothing */ # define MOZ_ONLY_USED_TO_AVOID_STATIC_CONSTRUCTORS /* nothing */ # define MOZ_IMPLICIT /* nothing */ # define MOZ_IS_SMARTPTR_TO_REFCOUNTED /* nothing */ # define MOZ_IS_REFPTR /* 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 */ # define MOZ_NEEDS_NO_VTABLE_TYPE /* nothing */ # define MOZ_NON_MEMMOVABLE /* nothing */ # define MOZ_NEEDS_MEMMOVABLE_TYPE /* nothing */ # define MOZ_NEEDS_MEMMOVABLE_MEMBERS /* nothing */ # define MOZ_NO_DANGLING_ON_TEMPORARIES /* nothing */ # define MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS /* nothing */ # define MOZ_INIT_OUTSIDE_CTOR /* nothing */ # define MOZ_IS_CLASS_INIT /* nothing */ # define MOZ_NON_PARAM /* nothing */ # define MOZ_NON_AUTOABLE /* nothing */ # define MOZ_REQUIRED_BASE_METHOD /* nothing */ # define MOZ_MUST_RETURN_FROM_CALLER_IF_THIS_IS_ARG /* nothing */ # define MOZ_MAY_CALL_AFTER_MUST_RETURN /* nothing */ # define MOZ_KNOWN_LIVE /* nothing */ # define MOZ_UNANNOTATED /* nothing */ # define MOZ_ANNOTATED /* nothing */ # endif /* defined(MOZ_CLANG_PLUGIN) || defined(XGILL_PLUGIN) */ # define MOZ_RAII MOZ_NON_TEMPORARY_CLASS MOZ_STACK_CLASS // XGILL_PLUGIN is used for the GC rooting hazard analysis, which compiles with // gcc. gcc has different rules governing __attribute__((...)) placement, so // some attributes will error out when used in the source code where clang // expects them to be. Remove the problematic annotations when needed. // // The placement of c++11 [[...]] attributes is more flexible and defined by a // spec, so it would be nice to switch to those for the problematic // cases. Unfortunately, the official spec provides *no* way to annotate a // lambda function, which is one source of the difficulty here. It appears that // this will be fixed in c++23: https://github.com/cplusplus/papers/issues/882 # ifdef XGILL_PLUGIN # undef MOZ_MUST_OVERRIDE # undef MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION # undef MOZ_CAN_RUN_SCRIPT # undef MOZ_CAN_RUN_SCRIPT_BOUNDARY # define MOZ_MUST_OVERRIDE /* nothing */ # define MOZ_CAN_RUN_SCRIPT_FOR_DEFINITION /* nothing */ # define MOZ_CAN_RUN_SCRIPT /* nothing */ # define MOZ_CAN_RUN_SCRIPT_BOUNDARY /* nothing */ # endif #endif /* __cplusplus */ /** * Printf style formats. MOZ_FORMAT_PRINTF and MOZ_FORMAT_WPRINTF can be used * to annotate a function or method that is "printf/wprintf-like"; this will let * (some) compilers check that the arguments match the template string. * * This macro takes two arguments. The first argument is the argument * number of the template string. The second argument is the argument * number of the '...' argument holding the arguments. * * Argument numbers start at 1. Note that the implicit "this" * argument of a non-static member function counts as an argument. * * So, for a simple case like: * void print_something (int whatever, const char *fmt, ...); * The corresponding annotation would be * MOZ_FORMAT_PRINTF(2, 3) * However, if "print_something" were a non-static member function, * then the annotation would be: * MOZ_FORMAT_PRINTF(3, 4) * * The second argument should be 0 for vprintf-like functions; that * is, those taking a va_list argument. * * Note that the checking is limited to standards-conforming * printf-likes, and in particular this should not be used for * PR_snprintf and friends, which are "printf-like" but which assign * different meanings to the various formats. * * MinGW requires special handling due to different format specifiers * on different platforms. The macro __MINGW_PRINTF_FORMAT maps to * either gnu_printf or ms_printf depending on where we are compiling * to avoid warnings on format specifiers that are legal. * * At time of writing MinGW has no wide equivalent to __MINGW_PRINTF_FORMAT; * therefore __MINGW_WPRINTF_FORMAT has been implemented following the same * pattern seen in MinGW's source. */ #ifdef __MINGW32__ # define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck) \ __attribute__((format(__MINGW_PRINTF_FORMAT, stringIndex, firstToCheck))) # ifndef __MINGW_WPRINTF_FORMAT # if defined(__clang__) # define __MINGW_WPRINTF_FORMAT wprintf # elif defined(_UCRT) || __USE_MINGW_ANSI_STDIO # define __MINGW_WPRINTF_FORMAT gnu_wprintf # else # define __MINGW_WPRINTF_FORMAT ms_wprintf # endif # endif # define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck) \ __attribute__((format(__MINGW_WPRINTF_FORMAT, stringIndex, firstToCheck))) #elif __GNUC__ || __clang__ # define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck) \ __attribute__((format(printf, stringIndex, firstToCheck))) # define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck) \ __attribute__((format(wprintf, stringIndex, firstToCheck))) #else # define MOZ_FORMAT_PRINTF(stringIndex, firstToCheck) # define MOZ_FORMAT_WPRINTF(stringIndex, firstToCheck) #endif /** * To manually declare an XPCOM ABI-compatible virtual function, the following * macros can be used to handle the non-standard ABI used on Windows for COM * compatibility. E.g.: * * virtual ReturnType MOZ_XPCOM_ABI foo(); */ #if defined(XP_WIN) # define MOZ_XPCOM_ABI __stdcall #else # define MOZ_XPCOM_ABI #endif /** * MSVC / clang-cl don't optimize empty bases correctly unless we explicitly * tell it to, see: * * https://stackoverflow.com/questions/12701469/why-is-the-empty-base-class-optimization-ebo-is-not-working-in-msvc * https://devblogs.microsoft.com/cppblog/optimizing-the-layout-of-empty-base-classes-in-vs2015-update-2-3/ */ #if defined(_MSC_VER) # define MOZ_EMPTY_BASES __declspec(empty_bases) #else # define MOZ_EMPTY_BASES #endif #endif /* mozilla_Attributes_h */