The Tor Browser: mfbt/Attributes.h@97036ab72558 (annotated)

mfbt/Attributes.h@97036ab72558 (annotated)

mfbt/Attributes.h

Tue, 06 Jan 2015 21:39:09 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Tue, 06 Jan 2015 21:39:09 +0100
branch: TOR_BUG_9701
changeset 8: 97036ab72558
permissions: -rw-r--r--

Conditionally force memory storage according to privacy.thirdparty.isolate;
This solves Tor bug #9701, complying with disk avoidance documented in
https://www.torproject.org/projects/torbrowser/design/#disk-avoidance.

 /* -*- 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<typename T>
  *   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 */

The Tor Browser / annotate

mfbt/Attributes.h@97036ab72558 (annotated)

mfbt/Attributes.h