Adding upstream version 1:115.7.0.upstream/1%115.7.0upstream

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

1 files changed, 647 insertions, 0 deletions

diff --git a/mfbt/Assertions.h b/mfbt/Assertions.h
new file mode 100644
index 0000000000..8c8b52405e
--- /dev/null
+++ b/mfbt/Assertions.h
@@ -0,0 +1,647 @@
+/* -*- 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(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API)) && \
+    !defined(__wasi__)
+#  define MOZ_DUMP_ASSERTION_STACK
+#endif
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Compiler.h"
+#include "mozilla/Fuzzing.h"
+#include "mozilla/Likely.h"
+#include "mozilla/MacroArgs.h"
+#include "mozilla/StaticAnalysisFunctions.h"
+#include "mozilla/Types.h"
+#ifdef MOZ_DUMP_ASSERTION_STACK
+#  include "mozilla/StackWalk.h"
+#endif
+
+/*
+ * 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
+
+#if defined(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API)
+static inline void AnnotateMozCrashReason(const char* reason) {
+  gMozCrashReason = reason;
+  // See bug 1681846, on 32-bit Android ARM the compiler removes the store to
+  // gMozCrashReason if this barrier is not present.
+  asm volatile("" ::: "memory");
+}
+#  define MOZ_CRASH_ANNOTATE(...) AnnotateMozCrashReason(__VA_ARGS__)
+#else
+#  define MOZ_CRASH_ANNOTATE(...) \
+    do { /* nothing */            \
+    } while (false)
+#endif
+
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+#ifdef _MSC_VER
+/*
+ * 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.
+ */
+MOZ_BEGIN_EXTERN_C
+__declspec(dllimport) int __stdcall TerminateProcess(void* hProcess,
+                                                     unsigned int uExitCode);
+__declspec(dllimport) void* __stdcall GetCurrentProcess(void);
+MOZ_END_EXTERN_C
+#elif defined(__wasi__)
+/*
+ * On Wasm/WASI platforms, we just call __builtin_trap().
+ */
+#else
+#  include <signal.h>
+#endif
+#ifdef ANDROID
+#  include <android/log.h>
+#endif
+
+MOZ_BEGIN_EXTERN_C
+
+#if defined(ANDROID) && defined(MOZ_DUMP_ASSERTION_STACK)
+MOZ_MAYBE_UNUSED static void MOZ_ReportAssertionFailurePrintFrame(
+    const char* aBuf) {
+  __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert", "%s\n", aBuf);
+}
+#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.
+ */
+MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
+MOZ_ReportAssertionFailure(const char* aStr, const char* aFilename,
+                           int aLine) MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS {
+  MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_ASSERT", aFilename, aLine, aStr);
+#ifdef ANDROID
+  __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert",
+                      "Assertion failure: %s, at %s:%d\n", aStr, aFilename,
+                      aLine);
+#  if defined(MOZ_DUMP_ASSERTION_STACK)
+  MozWalkTheStackWithWriter(MOZ_ReportAssertionFailurePrintFrame, CallerPC(),
+                            /* aMaxFrames */ 0);
+#  endif
+#else
+  fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
+#  if defined(MOZ_DUMP_ASSERTION_STACK)
+  MozWalkTheStack(stderr, CallerPC(), /* aMaxFrames */ 0);
+#  endif
+  fflush(stderr);
+#endif
+}
+
+MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_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)
+  MozWalkTheStack(stderr, CallerPC(), /* aMaxFrames */ 0);
+#  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 __LINE__ to prevent the compiler from folding multiple crash sites
+ * together, which would make crash reports hard to understand.
+ *
+ * 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.
+ *
+ * (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.)
+ */
+
+MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
+MOZ_NoReturn(int aLine) {
+  *((volatile int*)NULL) = aLine;
+  TerminateProcess(GetCurrentProcess(), 3);
+}
+
+#  define MOZ_REALLY_CRASH(line) \
+    do {                         \
+      __debugbreak();            \
+      MOZ_NoReturn(line);        \
+    } while (false)
+
+#elif __wasi__
+
+#  define MOZ_REALLY_CRASH(line) __builtin_trap()
+
+#else
+
+/*
+ * MOZ_CRASH_WRITE_ADDR is the address to be used when performing a forced
+ * crash. NULL is preferred however if for some reason NULL cannot be used
+ * this makes choosing another value possible.
+ *
+ * In the case of UBSan certain checks, bounds specifically, cause the compiler
+ * to emit the 'ud2' instruction when storing to 0x0. This causes forced
+ * crashes to manifest as ILL (at an arbitrary address) instead of the expected
+ * SEGV at 0x0.
+ */
+#  ifdef MOZ_UBSAN
+#    define MOZ_CRASH_WRITE_ADDR 0x1
+#  else
+#    define MOZ_CRASH_WRITE_ADDR NULL
+#  endif
+
+#  ifdef __cplusplus
+#    define MOZ_REALLY_CRASH(line)                                  \
+      do {                                                          \
+        *((volatile int*)MOZ_CRASH_WRITE_ADDR) = line; /* NOLINT */ \
+        ::abort();                                                  \
+      } while (false)
+#  else
+#    define MOZ_REALLY_CRASH(line)                                  \
+      do {                                                          \
+        *((volatile int*)MOZ_CRASH_WRITE_ADDR) = line; /* NOLINT */ \
+        abort();                                                    \
+      } while (false)
+#  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.
+ */
+#if !(defined(DEBUG) || defined(FUZZING))
+#  define MOZ_CRASH(...)                                                      \
+    do {                                                                      \
+      MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", __FILE__, __LINE__, NULL); \
+      MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")");                       \
+      MOZ_REALLY_CRASH(__LINE__);                                             \
+    } while (false)
+#else
+#  define MOZ_CRASH(...)                                                      \
+    do {                                                                      \
+      MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", __FILE__, __LINE__, NULL); \
+      MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__);                    \
+      MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")");                       \
+      MOZ_REALLY_CRASH(__LINE__);                                             \
+    } while (false)
+#endif
+
+/*
+ * MOZ_CRASH_UNSAFE(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.
+ *
+ * @note This macro causes data collection because crash strings are annotated
+ * to crash-stats and are publicly visible. Firefox data stewards must do data
+ * review on usages of this macro.
+ */
+static MOZ_ALWAYS_INLINE_EVEN_DEBUG MOZ_COLD MOZ_NORETURN void MOZ_Crash(
+    const char* aFilename, int aLine, const char* aReason) {
+  MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", aFilename, aLine, aReason);
+#if defined(DEBUG) || defined(FUZZING)
+  MOZ_ReportCrash(aReason, aFilename, aLine);
+#endif
+  MOZ_CRASH_ANNOTATE(aReason);
+  MOZ_REALLY_CRASH(aLine);
+}
+#define MOZ_CRASH_UNSAFE(reason) MOZ_Crash(__FILE__, __LINE__, reason)
+
+static const size_t sPrintfMaxArgs = 4;
+static const size_t sPrintfCrashReasonSize = 1024;
+
+MFBT_API MOZ_COLD MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(1, 2) const
+    char* MOZ_CrashPrintf(const char* aFormat, ...);
+
+/*
+ * 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.
+ *
+ * @note This macro causes data collection because crash strings are annotated
+ * to crash-stats and are publicly visible. Firefox data stewards must do data
+ * review on usages of this macro.
+ */
+#define MOZ_CRASH_UNSAFE_PRINTF(format, ...)                                \
+  do {                                                                      \
+    static_assert(MOZ_ARG_COUNT(__VA_ARGS__) > 0,                           \
+                  "Did you forget arguments to MOZ_CRASH_UNSAFE_PRINTF? "   \
+                  "Or maybe you want MOZ_CRASH instead?");                  \
+    static_assert(MOZ_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_Crash(__FILE__, __LINE__, MOZ_CrashPrintf("" format, __VA_ARGS__)); \
+  } while (false)
+
+MOZ_END_EXTERN_C
+
+/*
+ * 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.
+ *
+ * MOZ_DIAGNOSTIC_ASSERT_ENABLED is defined when MOZ_DIAGNOSTIC_ASSERT is like
+ * MOZ_RELEASE_ASSERT rather than MOZ_ASSERT.
+ */
+
+/*
+ * 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 <type_traits>
+namespace mozilla {
+namespace detail {
+
+template <typename T>
+struct AssertionConditionType {
+  using ValueT = std::remove_reference_t<T>;
+  static_assert(!std::is_array_v<ValueT>,
+                "Expected boolean assertion condition, got an array or a "
+                "string!");
+  static_assert(!std::is_function_v<ValueT>,
+                "Expected boolean assertion condition, got a function! Did "
+                "you intend to call that function?");
+  static_assert(!std::is_floating_point_v<ValueT>,
+                "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
+
+#if defined(DEBUG) || defined(MOZ_ASAN)
+#  define MOZ_REPORT_ASSERTION_FAILURE(...) \
+    MOZ_ReportAssertionFailure(__VA_ARGS__)
+#else
+#  define MOZ_REPORT_ASSERTION_FAILURE(...) \
+    do { /* nothing */                      \
+    } while (false)
+#endif
+
+/* First the single-argument form. */
+#define MOZ_ASSERT_HELPER1(kind, expr)                         \
+  do {                                                         \
+    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr);                  \
+    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) {    \
+      MOZ_FUZZING_HANDLE_CRASH_EVENT2(kind, #expr);            \
+      MOZ_REPORT_ASSERTION_FAILURE(#expr, __FILE__, __LINE__); \
+      MOZ_CRASH_ANNOTATE(kind "(" #expr ")");                  \
+      MOZ_REALLY_CRASH(__LINE__);                              \
+    }                                                          \
+  } while (false)
+/* Now the two-argument form. */
+#define MOZ_ASSERT_HELPER2(kind, expr, explain)                      \
+  do {                                                               \
+    MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr);                        \
+    if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) {          \
+      MOZ_FUZZING_HANDLE_CRASH_EVENT2(kind, #expr);                  \
+      MOZ_REPORT_ASSERTION_FAILURE(#expr " (" explain ")", __FILE__, \
+                                   __LINE__);                        \
+      MOZ_CRASH_ANNOTATE(kind "(" #expr ") (" explain ")");          \
+      MOZ_REALLY_CRASH(__LINE__);                                    \
+    }                                                                \
+  } while (false)
+
+#define MOZ_ASSERT_GLUE(a, b) a b
+#define MOZ_RELEASE_ASSERT(...)                                       \
+  MOZ_ASSERT_GLUE(                                                    \
+      MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
+      ("MOZ_RELEASE_ASSERT", __VA_ARGS__))
+
+#ifdef DEBUG
+#  define MOZ_ASSERT(...)                                               \
+    MOZ_ASSERT_GLUE(                                                    \
+        MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
+        ("MOZ_ASSERT", __VA_ARGS__))
+#else
+#  define MOZ_ASSERT(...) \
+    do {                  \
+    } while (false)
+#endif /* DEBUG */
+
+#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
+#  define MOZ_DIAGNOSTIC_ASSERT(...)                                    \
+    MOZ_ASSERT_GLUE(                                                    \
+        MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
+        ("MOZ_DIAGNOSTIC_ASSERT", __VA_ARGS__))
+#else
+#  define MOZ_DIAGNOSTIC_ASSERT(...) \
+    do {                             \
+    } while (false)
+#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 (false)
+#else
+#  define MOZ_ASSERT_IF(cond, expr) \
+    do {                            \
+    } while (false)
+#endif
+
+/*
+ * MOZ_DIAGNOSTIC_ASSERT_IF is like MOZ_ASSERT_IF, but using
+ * MOZ_DIAGNOSTIC_ASSERT as the underlying assert.
+ *
+ * See the block comment for MOZ_DIAGNOSTIC_ASSERT above for more details on how
+ * diagnostic assertions work and how to use them.
+ */
+#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
+#  define MOZ_DIAGNOSTIC_ASSERT_IF(cond, expr) \
+    do {                                       \
+      if (cond) {                              \
+        MOZ_DIAGNOSTIC_ASSERT(expr);           \
+      }                                        \
+    } while (false)
+#else
+#  define MOZ_DIAGNOSTIC_ASSERT_IF(cond, expr) \
+    do {                                       \
+    } while (false)
+#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 (false)
+
+/**
+ * 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 [[fallthrough]]? In
+ * release builds, the MOZ_ASSERT(false) will expand to `do { } while (false)`,
+ * requiring a [[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 [[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!
+ *     [[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(...) \
+    MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " __VA_ARGS__)
+#else
+#  define MOZ_FALLTHROUGH_ASSERT(...) [[fallthrough]]
+#endif
+
+/*
+ * MOZ_ALWAYS_TRUE(expr) and friends always evaluate the provided expression,
+ * in debug builds and in release builds both.  Then, in debug builds and
+ * Nightly and DevEdition release builds, the value of the expression is
+ * asserted either true or false using MOZ_DIAGNOSTIC_ASSERT.
+ */
+#define MOZ_ALWAYS_TRUE(expr)              \
+  do {                                     \
+    if (MOZ_LIKELY(expr)) {                \
+      /* Silence [[nodiscard]]. */         \
+    } else {                               \
+      MOZ_DIAGNOSTIC_ASSERT(false, #expr); \
+    }                                      \
+  } while (false)
+
+#define MOZ_ALWAYS_FALSE(expr) MOZ_ALWAYS_TRUE(!(expr))
+#define MOZ_ALWAYS_OK(expr) MOZ_ALWAYS_TRUE((expr).isOk())
+#define MOZ_ALWAYS_ERR(expr) MOZ_ALWAYS_TRUE((expr).isErr())
+
+/*
+ * These are disabled when fuzzing
+ */
+#ifdef FUZZING
+#  define MOZ_CRASH_UNLESS_FUZZING(...) \
+    do {                                \
+    } while (0)
+#  define MOZ_ASSERT_UNLESS_FUZZING(...) \
+    do {                                 \
+    } while (0)
+#else
+#  define MOZ_CRASH_UNLESS_FUZZING(...) MOZ_CRASH(__VA_ARGS__)
+#  define MOZ_ASSERT_UNLESS_FUZZING(...) MOZ_ASSERT(__VA_ARGS__)
+#endif
+
+#undef MOZ_DUMP_ASSERTION_STACK
+#undef MOZ_CRASH_CRASHREPORT
+
+/*
+ * This is only used by Array and nsTArray classes, therefore it is not
+ * required when included from C code.
+ */
+#ifdef __cplusplus
+namespace mozilla::detail {
+MFBT_API MOZ_NORETURN MOZ_COLD void InvalidArrayIndex_CRASH(size_t aIndex,
+                                                            size_t aLength);
+}  // namespace mozilla::detail
+#endif  // __cplusplus
+
+#endif /* mozilla_Assertions_h */