text: /* -*- 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<typename T>
   *   class Ptr
   *   {
   *     T* mPtr;
   *     MOZ_EXPLICIT_CONVERSION operator bool() const
   *     {
   *       return mPtr != nullptr;
   *     }
   *   };
   *
   */
  #ifdef MOZ_HAVE_EXPLICIT_CONVERSION
  #  define MOZ_EXPLICIT_CONVERSION explicit
  #else
  #  define MOZ_EXPLICIT_CONVERSION /* no support */
  #endif
  
  /*
   * MOZ_NEVER_INLINE is a macro which expands to tell the compiler that the
   * method decorated with it must never be inlined, even if the compiler would
   * otherwise choose to inline the method.  Compilers aren't absolutely
   * guaranteed to support this, but most do.
   */
  #if defined(MOZ_HAVE_NEVER_INLINE)
  #  define MOZ_NEVER_INLINE      MOZ_HAVE_NEVER_INLINE
  #else
  #  define MOZ_NEVER_INLINE      /* no support */
  #endif
  
  /*
   * MOZ_NORETURN, specified at the start of a function declaration, indicates
   * that the given function does not return.  (The function definition does not
   * need to be annotated.)
   *
   *   MOZ_NORETURN void abort(const char* msg);
   *
   * This modifier permits the compiler to optimize code assuming a call to such a
   * function will never return.  It also enables the compiler to avoid spurious
   * warnings about not initializing variables, or about any other seemingly-dodgy
   * operations performed after the function returns.
   *
   * This modifier does not affect the corresponding function's linking behavior.
   */
  #if defined(MOZ_HAVE_NORETURN)
  #  define MOZ_NORETURN          MOZ_HAVE_NORETURN
  #else
  #  define MOZ_NORETURN          /* no support */
  #endif
  
  /*
   * MOZ_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& aOther) MOZ_DELETE;
   *     void operator=(const NonCopyable& aOther) 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 */
  