Add m-esr52 at 52.6.0

1 files changed, 637 insertions, 0 deletions

diff --git a/mfbt/Assertions.h b/mfbt/Assertions.h
new file mode 100644
index 000000000..e7b010b7f
--- /dev/null
+++ b/mfbt/Assertions.h
@@ -0,0 +1,637 @@
+/* -*- 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 runtime and static assertion macros for C and C++. */
+
+#ifndef mozilla_Assertions_h
+#define mozilla_Assertions_h
+
+#if defined(MOZILLA_INTERNAL_API) && defined(__cplusplus)
+#define MOZ_DUMP_ASSERTION_STACK
+#endif
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Compiler.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MacroArgs.h"
+#include "mozilla/StaticAnalysisFunctions.h"
+#include "mozilla/Types.h"
+#ifdef MOZ_DUMP_ASSERTION_STACK
+#include "nsTraceRefcnt.h"
+#endif
+
+#if defined(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API)
+/*
+ * The crash reason set by MOZ_CRASH_ANNOTATE is consumed by the crash reporter
+ * if present. It is declared here (and defined in Assertions.cpp) to make it
+ * available to all code, even libraries that don't link with the crash reporter
+ * directly.
+ */
+MOZ_BEGIN_EXTERN_C
+extern MFBT_DATA const char* gMozCrashReason;
+MOZ_END_EXTERN_C
+
+static inline void
+AnnotateMozCrashReason(const char* reason)
+{
+  gMozCrashReason = reason;
+}
+#  define MOZ_CRASH_ANNOTATE(...) AnnotateMozCrashReason(__VA_ARGS__)
+#else
+#  define MOZ_CRASH_ANNOTATE(...) do { /* nothing */ } while (0)
+#endif
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef WIN32
+   /*
+    * TerminateProcess and GetCurrentProcess are defined in <winbase.h>, which
+    * further depends on <windef.h>.  We hardcode these few definitions manually
+    * because those headers clutter the global namespace with a significant
+    * number of undesired macros and symbols.
+    */
+#  ifdef __cplusplus
+extern "C" {
+#  endif
+__declspec(dllimport) int __stdcall
+TerminateProcess(void* hProcess, unsigned int uExitCode);
+__declspec(dllimport) void* __stdcall GetCurrentProcess(void);
+#  ifdef __cplusplus
+}
+#  endif
+#else
+#  include <signal.h>
+#endif
+#ifdef ANDROID
+#  include <android/log.h>
+#endif
+
+/*
+ * MOZ_STATIC_ASSERT may be used to assert a condition *at compile time* in C.
+ * In C++11, static_assert is provided by the compiler to the same effect.
+ * This can be useful when you make certain assumptions about what must hold for
+ * optimal, or even correct, behavior.  For example, you might assert that the
+ * size of a struct is a multiple of the target architecture's word size:
+ *
+ *   struct S { ... };
+ *   // C
+ *   MOZ_STATIC_ASSERT(sizeof(S) % sizeof(size_t) == 0,
+ *                     "S should be a multiple of word size for efficiency");
+ *   // C++11
+ *   static_assert(sizeof(S) % sizeof(size_t) == 0,
+ *                 "S should be a multiple of word size for efficiency");
+ *
+ * This macro can be used in any location where both an extern declaration and a
+ * typedef could be used.
+ */
+#ifndef __cplusplus
+   /*
+    * Some of the definitions below create an otherwise-unused typedef.  This
+    * triggers compiler warnings with some versions of gcc, so mark the typedefs
+    * as permissibly-unused to disable the warnings.
+    */
+#  if defined(__GNUC__)
+#    define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE __attribute__((unused))
+#  else
+#    define MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE /* nothing */
+#  endif
+#  define MOZ_STATIC_ASSERT_GLUE1(x, y)          x##y
+#  define MOZ_STATIC_ASSERT_GLUE(x, y)           MOZ_STATIC_ASSERT_GLUE1(x, y)
+#  if defined(__SUNPRO_CC)
+     /*
+      * The Sun Studio C++ compiler is buggy when declaring, inside a function,
+      * another extern'd function with an array argument whose length contains a
+      * sizeof, triggering the error message "sizeof expression not accepted as
+      * size of array parameter".  This bug (6688515, not public yet) would hit
+      * defining moz_static_assert as a function, so we always define an extern
+      * array for Sun Studio.
+      *
+      * We include the line number in the symbol name in a best-effort attempt
+      * to avoid conflicts (see below).
+      */
+#    define MOZ_STATIC_ASSERT(cond, reason) \
+       extern char MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)[(cond) ? 1 : -1]
+#  elif defined(__COUNTER__)
+     /*
+      * If there was no preferred alternative, use a compiler-agnostic version.
+      *
+      * Note that the non-__COUNTER__ version has a bug in C++: it can't be used
+      * in both |extern "C"| and normal C++ in the same translation unit.  (Alas
+      * |extern "C"| isn't allowed in a function.)  The only affected compiler
+      * we really care about is gcc 4.2.  For that compiler and others like it,
+      * we include the line number in the function name to do the best we can to
+      * avoid conflicts.  These should be rare: a conflict would require use of
+      * MOZ_STATIC_ASSERT on the same line in separate files in the same
+      * translation unit, *and* the uses would have to be in code with
+      * different linkage, *and* the first observed use must be in C++-linkage
+      * code.
+      */
+#    define MOZ_STATIC_ASSERT(cond, reason) \
+       typedef int MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __COUNTER__)[(cond) ? 1 : -1] MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
+#  else
+#    define MOZ_STATIC_ASSERT(cond, reason) \
+       extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1]) MOZ_STATIC_ASSERT_UNUSED_ATTRIBUTE
+#  endif
+
+#define MOZ_STATIC_ASSERT_IF(cond, expr, reason)  MOZ_STATIC_ASSERT(!(cond) || (expr), reason)
+#else
+#define MOZ_STATIC_ASSERT_IF(cond, expr, reason)  static_assert(!(cond) || (expr), reason)
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+ * Prints |aStr| as an assertion failure (using aFilename and aLine as the
+ * location of the assertion) to the standard debug-output channel.
+ *
+ * Usually you should use MOZ_ASSERT or MOZ_CRASH instead of this method.  This
+ * method is primarily for internal use in this header, and only secondarily
+ * for use in implementing release-build assertions.
+ */
+static MOZ_COLD MOZ_ALWAYS_INLINE void
+MOZ_ReportAssertionFailure(const char* aStr, const char* aFilename, int aLine)
+  MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
+{
+#ifdef ANDROID
+  __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert",
+                      "Assertion failure: %s, at %s:%d\n",
+                      aStr, aFilename, aLine);
+#else
+  fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
+#if defined (MOZ_DUMP_ASSERTION_STACK)
+  nsTraceRefcnt::WalkTheStack(stderr);
+#endif
+  fflush(stderr);
+#endif
+}
+
+static MOZ_COLD MOZ_ALWAYS_INLINE void
+MOZ_ReportCrash(const char* aStr, const char* aFilename, int aLine)
+  MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS
+{
+#ifdef ANDROID
+  __android_log_print(ANDROID_LOG_FATAL, "MOZ_CRASH",
+                      "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
+#else
+  fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
+#if defined(MOZ_DUMP_ASSERTION_STACK)
+  nsTraceRefcnt::WalkTheStack(stderr);
+#endif
+  fflush(stderr);
+#endif
+}
+
+/**
+ * MOZ_REALLY_CRASH is used in the implementation of MOZ_CRASH().  You should
+ * call MOZ_CRASH instead.
+ */
+#if defined(_MSC_VER)
+   /*
+    * On MSVC use the __debugbreak compiler intrinsic, which produces an inline
+    * (not nested in a system function) breakpoint.  This distinctively invokes
+    * Breakpad without requiring system library symbols on all stack-processing
+    * machines, as a nested breakpoint would require.
+    *
+    * We use TerminateProcess with the exit code aborting would generate
+    * because we don't want to invoke atexit handlers, destructors, library
+    * unload handlers, and so on when our process might be in a compromised
+    * state.
+    *
+    * We don't use abort() because it'd cause Windows to annoyingly pop up the
+    * process error dialog multiple times.  See bug 345118 and bug 426163.
+    *
+    * We follow TerminateProcess() with a call to MOZ_NoReturn() so that the
+    * compiler doesn't hassle us to provide a return statement after a
+    * MOZ_REALLY_CRASH() call.
+    *
+    * (Technically these are Windows requirements, not MSVC requirements.  But
+    * practically you need MSVC for debugging, and we only ship builds created
+    * by MSVC, so doing it this way reduces complexity.)
+    */
+
+__declspec(noreturn) __inline void MOZ_NoReturn() {}
+
+#  ifdef __cplusplus
+#    define MOZ_REALLY_CRASH(line) \
+       do { \
+         ::__debugbreak(); \
+         *((volatile int*) NULL) = line; \
+         ::TerminateProcess(::GetCurrentProcess(), 3); \
+         ::MOZ_NoReturn(); \
+       } while (0)
+#  else
+#    define MOZ_REALLY_CRASH(line) \
+       do { \
+         __debugbreak(); \
+         *((volatile int*) NULL) = line; \
+         TerminateProcess(GetCurrentProcess(), 3); \
+         MOZ_NoReturn(); \
+       } while (0)
+#  endif
+#else
+#  ifdef __cplusplus
+#    define MOZ_REALLY_CRASH(line) \
+       do { \
+         *((volatile int*) NULL) = line; \
+         ::abort(); \
+       } while (0)
+#  else
+#    define MOZ_REALLY_CRASH(line) \
+       do { \
+         *((volatile int*) NULL) = line; \
+         abort(); \
+       } while (0)
+#  endif
+#endif
+
+/*
+ * MOZ_CRASH([explanation-string]) crashes the program, plain and simple, in a
+ * Breakpad-compatible way, in both debug and release builds.
+ *
+ * MOZ_CRASH is a good solution for "handling" failure cases when you're
+ * unwilling or unable to handle them more cleanly -- for OOM, for likely memory
+ * corruption, and so on.  It's also a good solution if you need safe behavior
+ * in release builds as well as debug builds.  But if the failure is one that
+ * should be debugged and fixed, MOZ_ASSERT is generally preferable.
+ *
+ * The optional explanation-string, if provided, must be a string literal
+ * explaining why we're crashing.  This argument is intended for use with
+ * MOZ_CRASH() calls whose rationale is non-obvious; don't use it if it's
+ * obvious why we're crashing.
+ *
+ * If we're a DEBUG build and we crash at a MOZ_CRASH which provides an
+ * explanation-string, we print the string to stderr.  Otherwise, we don't
+ * print anything; this is because we want MOZ_CRASH to be 100% safe in release
+ * builds, and it's hard to print to stderr safely when memory might have been
+ * corrupted.
+ */
+#ifndef DEBUG
+#  define MOZ_CRASH(...) \
+     do { \
+       MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
+       MOZ_REALLY_CRASH(__LINE__); \
+     } while (0)
+#else
+#  define MOZ_CRASH(...) \
+     do { \
+       MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \
+       MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
+       MOZ_REALLY_CRASH(__LINE__); \
+     } while (0)
+#endif
+
+/*
+ * MOZ_CRASH_UNSAFE_OOL(explanation-string) can be used if the explanation
+ * string cannot be a string literal (but no other processing needs to be done
+ * on it). A regular MOZ_CRASH() is preferred wherever possible, as passing
+ * arbitrary strings from a potentially compromised process is not without risk.
+ * If the string being passed is the result of a printf-style function,
+ * consider using MOZ_CRASH_UNSAFE_PRINTF instead.
+ */
+#ifndef DEBUG
+MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
+MOZ_CrashOOL(int aLine, const char* aReason);
+#  define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__LINE__, reason)
+#else
+MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
+MOZ_CrashOOL(const char* aFilename, int aLine, const char* aReason);
+#  define MOZ_CRASH_UNSAFE_OOL(reason) MOZ_CrashOOL(__FILE__, __LINE__, reason)
+#endif
+
+static const size_t sPrintfMaxArgs = 4;
+static const size_t sPrintfCrashReasonSize = 1024;
+
+#ifndef DEBUG
+MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(2, 3) void
+MOZ_CrashPrintf(int aLine, const char* aFormat, ...);
+#  define MOZ_CALL_CRASH_PRINTF(format, ...) \
+     MOZ_CrashPrintf(__LINE__, format, __VA_ARGS__)
+#else
+MFBT_API MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(3, 4) void
+MOZ_CrashPrintf(const char* aFilename, int aLine, const char* aFormat, ...);
+#  define MOZ_CALL_CRASH_PRINTF(format, ...) \
+     MOZ_CrashPrintf(__FILE__, __LINE__, format, __VA_ARGS__)
+#endif
+
+/*
+ * MOZ_CRASH_UNSAFE_PRINTF(format, arg1 [, args]) can be used when more
+ * information is desired than a string literal can supply. The caller provides
+ * a printf-style format string, which must be a string literal and between
+ * 1 and 4 additional arguments. A regular MOZ_CRASH() is preferred wherever
+ * possible, as passing arbitrary strings to printf from a potentially
+ * compromised process is not without risk.
+ */
+#define MOZ_CRASH_UNSAFE_PRINTF(format, ...) \
+   do { \
+     MOZ_STATIC_ASSERT_VALID_ARG_COUNT(__VA_ARGS__); \
+     static_assert( \
+       MOZ_PASTE_PREFIX_AND_ARG_COUNT(, __VA_ARGS__) <= sPrintfMaxArgs, \
+       "Only up to 4 additional arguments are allowed!"); \
+     static_assert(sizeof(format) <= sPrintfCrashReasonSize, \
+       "The supplied format string is too long!"); \
+     MOZ_CALL_CRASH_PRINTF("" format, __VA_ARGS__); \
+   } while (0)
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+/*
+ * MOZ_ASSERT(expr [, explanation-string]) asserts that |expr| must be truthy in
+ * debug builds.  If it is, execution continues.  Otherwise, an error message
+ * including the expression and the explanation-string (if provided) is printed,
+ * an attempt is made to invoke any existing debugger, and execution halts.
+ * MOZ_ASSERT is fatal: no recovery is possible.  Do not assert a condition
+ * which can correctly be falsy.
+ *
+ * The optional explanation-string, if provided, must be a string literal
+ * explaining the assertion.  It is intended for use with assertions whose
+ * correctness or rationale is non-obvious, and for assertions where the "real"
+ * condition being tested is best described prosaically.  Don't provide an
+ * explanation if it's not actually helpful.
+ *
+ *   // No explanation needed: pointer arguments often must not be NULL.
+ *   MOZ_ASSERT(arg);
+ *
+ *   // An explanation can be helpful to explain exactly how we know an
+ *   // assertion is valid.
+ *   MOZ_ASSERT(state == WAITING_FOR_RESPONSE,
+ *              "given that <thingA> and <thingB>, we must have...");
+ *
+ *   // Or it might disambiguate multiple identical (save for their location)
+ *   // assertions of the same expression.
+ *   MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
+ *              "we already set [[PrimitiveThis]] for this Boolean object");
+ *   MOZ_ASSERT(getSlot(PRIMITIVE_THIS_SLOT).isUndefined(),
+ *              "we already set [[PrimitiveThis]] for this String object");
+ *
+ * MOZ_ASSERT has no effect in non-debug builds.  It is designed to catch bugs
+ * *only* during debugging, not "in the field". If you want the latter, use
+ * MOZ_RELEASE_ASSERT, which applies to non-debug builds as well.
+ *
+ * MOZ_DIAGNOSTIC_ASSERT works like MOZ_RELEASE_ASSERT in Nightly/Aurora and
+ * MOZ_ASSERT in Beta/Release - use this when a condition is potentially rare
+ * enough to require real user testing to hit, but is not security-sensitive.
+ * This can cause user pain, so use it sparingly. If a MOZ_DIAGNOSTIC_ASSERT
+ * is firing, it should promptly be converted to a MOZ_ASSERT while the failure
+ * is being investigated, rather than letting users suffer.
+ */
+
+/*
+ * Implement MOZ_VALIDATE_ASSERT_CONDITION_TYPE, which is used to guard against
+ * accidentally passing something unintended in lieu of an assertion condition.
+ */
+
+#ifdef __cplusplus
+#  include "mozilla/TypeTraits.h"
+namespace mozilla {
+namespace detail {
+
+template<typename T>
+struct AssertionConditionType
+{
+  typedef typename RemoveReference<T>::Type ValueT;
+  static_assert(!IsArray<ValueT>::value,
+                "Expected boolean assertion condition, got an array or a "
+                "string!");
+  static_assert(!IsFunction<ValueT>::value,
+                "Expected boolean assertion condition, got a function! Did "
+                "you intend to call that function?");
+  static_assert(!IsFloatingPoint<ValueT>::value,
+                "It's often a bad idea to assert that a floating-point number "
+                "is nonzero, because such assertions tend to intermittently "
+                "fail. Shouldn't your code gracefully handle this case instead "
+                "of asserting? Anyway, if you really want to do that, write an "
+                "explicit boolean condition, like !!x or x!=0.");
+
+  static const bool isValid = true;
+};
+
+} // namespace detail
+} // namespace mozilla
+#  define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x) \
+     static_assert(mozilla::detail::AssertionConditionType<decltype(x)>::isValid, \
+                   "invalid assertion condition")
+#else
+#  define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x)
+#endif
+
+/* First the single-argument form. */
+#define MOZ_ASSERT_HELPER1(expr) \
+  do { \
+    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
+    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
+      MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \
+      MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ")"); \
+      MOZ_REALLY_CRASH(__LINE__); \
+    } \
+  } while (0)
+/* Now the two-argument form. */
+#define MOZ_ASSERT_HELPER2(expr, explain) \
+  do { \
+    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
+    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
+      MOZ_ReportAssertionFailure(#expr " (" explain ")", __FILE__, __LINE__); \
+      MOZ_CRASH_ANNOTATE("MOZ_RELEASE_ASSERT(" #expr ") (" explain ")"); \
+      MOZ_REALLY_CRASH(__LINE__); \
+    } \
+  } while (0)
+
+#define MOZ_RELEASE_ASSERT_GLUE(a, b) a b
+#define MOZ_RELEASE_ASSERT(...) \
+  MOZ_RELEASE_ASSERT_GLUE( \
+    MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
+    (__VA_ARGS__))
+
+#ifdef DEBUG
+#  define MOZ_ASSERT(...) MOZ_RELEASE_ASSERT(__VA_ARGS__)
+#else
+#  define MOZ_ASSERT(...) do { } while (0)
+#endif /* DEBUG */
+
+#ifdef RELEASE_OR_BETA
+#  define MOZ_DIAGNOSTIC_ASSERT MOZ_ASSERT
+#else
+#  define MOZ_DIAGNOSTIC_ASSERT MOZ_RELEASE_ASSERT
+#endif
+
+/*
+ * MOZ_ASSERT_IF(cond1, cond2) is equivalent to MOZ_ASSERT(cond2) if cond1 is
+ * true.
+ *
+ *   MOZ_ASSERT_IF(isPrime(num), num == 2 || isOdd(num));
+ *
+ * As with MOZ_ASSERT, MOZ_ASSERT_IF has effect only in debug builds.  It is
+ * designed to catch bugs during debugging, not "in the field".
+ */
+#ifdef DEBUG
+#  define MOZ_ASSERT_IF(cond, expr) \
+     do { \
+       if (cond) { \
+         MOZ_ASSERT(expr); \
+       } \
+     } while (0)
+#else
+#  define MOZ_ASSERT_IF(cond, expr)  do { } while (0)
+#endif
+
+/*
+ * MOZ_ASSUME_UNREACHABLE_MARKER() expands to an expression which states that
+ * it is undefined behavior for execution to reach this point.  No guarantees
+ * are made about what will happen if this is reached at runtime.  Most code
+ * should use MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE because it has extra
+ * asserts.
+ */
+#if defined(__clang__) || defined(__GNUC__)
+#  define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable()
+#elif defined(_MSC_VER)
+#  define MOZ_ASSUME_UNREACHABLE_MARKER() __assume(0)
+#else
+#  ifdef __cplusplus
+#    define MOZ_ASSUME_UNREACHABLE_MARKER() ::abort()
+#  else
+#    define MOZ_ASSUME_UNREACHABLE_MARKER() abort()
+#  endif
+#endif
+
+/*
+ * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE([reason]) tells the compiler that it
+ * can assume that the macro call cannot be reached during execution.  This lets
+ * the compiler generate better-optimized code under some circumstances, at the
+ * expense of the program's behavior being undefined if control reaches the
+ * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE.
+ *
+ * In Gecko, you probably should not use this macro outside of performance- or
+ * size-critical code, because it's unsafe.  If you don't care about code size
+ * or performance, you should probably use MOZ_ASSERT or MOZ_CRASH.
+ *
+ * SpiderMonkey is a different beast, and there it's acceptable to use
+ * MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE more widely.
+ *
+ * Note that MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE is noreturn, so it's valid
+ * not to return a value following a MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE
+ * call.
+ *
+ * Example usage:
+ *
+ *   enum ValueType {
+ *     VALUE_STRING,
+ *     VALUE_INT,
+ *     VALUE_FLOAT
+ *   };
+ *
+ *   int ptrToInt(ValueType type, void* value) {
+ *   {
+ *     // We know for sure that type is either INT or FLOAT, and we want this
+ *     // code to run as quickly as possible.
+ *     switch (type) {
+ *     case VALUE_INT:
+ *       return *(int*) value;
+ *     case VALUE_FLOAT:
+ *       return (int) *(float*) value;
+ *     default:
+ *       MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE("Unexpected ValueType");
+ *     }
+ *   }
+ */
+
+/*
+ * Unconditional assert in debug builds for (assumed) unreachable code paths
+ * that have a safe return without crashing in release builds.
+ */
+#define MOZ_ASSERT_UNREACHABLE(reason) \
+   MOZ_ASSERT(false, "MOZ_ASSERT_UNREACHABLE: " reason)
+
+#define MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(reason) \
+   do { \
+     MOZ_ASSERT_UNREACHABLE(reason); \
+     MOZ_ASSUME_UNREACHABLE_MARKER(); \
+   } while (0)
+
+/**
+ * MOZ_FALLTHROUGH_ASSERT is an annotation to suppress compiler warnings about
+ * switch cases that MOZ_ASSERT(false) (or its alias MOZ_ASSERT_UNREACHABLE) in
+ * debug builds, but intentionally fall through in release builds to handle
+ * unexpected values.
+ *
+ * Why do we need MOZ_FALLTHROUGH_ASSERT in addition to MOZ_FALLTHROUGH? In
+ * release builds, the MOZ_ASSERT(false) will expand to `do { } while (0)`,
+ * requiring a MOZ_FALLTHROUGH annotation to suppress a -Wimplicit-fallthrough
+ * warning. In debug builds, the MOZ_ASSERT(false) will expand to something like
+ * `if (true) { MOZ_CRASH(); }` and the MOZ_FALLTHROUGH annotation will cause
+ * a -Wunreachable-code warning. The MOZ_FALLTHROUGH_ASSERT macro breaks this
+ * warning stalemate.
+ *
+ * // Example before MOZ_FALLTHROUGH_ASSERT:
+ * switch (foo) {
+ *   default:
+ *     // This case wants to assert in debug builds, fall through in release.
+ *     MOZ_ASSERT(false); // -Wimplicit-fallthrough warning in release builds!
+ *     MOZ_FALLTHROUGH;   // but -Wunreachable-code warning in debug builds!
+ *   case 5:
+ *     return 5;
+ * }
+ *
+ * // Example with MOZ_FALLTHROUGH_ASSERT:
+ * switch (foo) {
+ *   default:
+ *     // This case asserts in debug builds, falls through in release.
+ *     MOZ_FALLTHROUGH_ASSERT("Unexpected foo value?!");
+ *   case 5:
+ *     return 5;
+ * }
+ */
+#ifdef DEBUG
+#  define MOZ_FALLTHROUGH_ASSERT(reason) MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " reason)
+#else
+#  define MOZ_FALLTHROUGH_ASSERT(...) MOZ_FALLTHROUGH
+#endif
+
+/*
+ * MOZ_ALWAYS_TRUE(expr) and MOZ_ALWAYS_FALSE(expr) always evaluate the provided
+ * expression, in debug builds and in release builds both.  Then, in debug
+ * builds only, the value of the expression is asserted either true or false
+ * using MOZ_ASSERT.
+ */
+#ifdef DEBUG
+#  define MOZ_ALWAYS_TRUE(expr) \
+     do { \
+       if ((expr)) { \
+         /* Do nothing. */ \
+       } else { \
+         MOZ_ASSERT(false, #expr); \
+       } \
+     } while (0)
+#  define MOZ_ALWAYS_FALSE(expr) \
+     do { \
+       if ((expr)) { \
+         MOZ_ASSERT(false, #expr); \
+       } else { \
+         /* Do nothing. */ \
+       } \
+     } while (0)
+#else
+#  define MOZ_ALWAYS_TRUE(expr) \
+     do { \
+       if ((expr)) { \
+          /* Silence MOZ_MUST_USE. */ \
+       } \
+     } while (0)
+#  define MOZ_ALWAYS_FALSE(expr) \
+     do { \
+       if ((expr)) { \
+         /* Silence MOZ_MUST_USE. */ \
+       } \
+     } while (0)
+#endif
+
+#undef MOZ_DUMP_ASSERTION_STACK
+#undef MOZ_CRASH_CRASHREPORT
+
+#endif /* mozilla_Assertions_h */