Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1034 insertions, 0 deletions

diff --git a/mfbt/Attributes.h b/mfbt/Attributes.h
new file mode 100644
index 0000000000..b4b0316a3a
--- /dev/null
+++ b/mfbt/Attributes.h
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+/* -*- 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<unsigned int>(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 */