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Diffstat (limited to '')
| -rw-r--r-- | mfbt/Assertions.h | 709 |
1 files changed, 709 insertions, 0 deletions
diff --git a/mfbt/Assertions.h b/mfbt/Assertions.h new file mode 100644 index 0000000000..634d340579 --- /dev/null +++ b/mfbt/Assertions.h @@ -0,0 +1,709 @@ +/* -*- 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 +#if defined(XP_WIN) && (defined(DEBUG) || defined(FUZZING)) +# define MOZ_BUFFER_STDERR +#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 +# if defined(MOZ_BUFFER_STDERR) + char msg[1024] = ""; + snprintf(msg, sizeof(msg) - 1, "Assertion failure: %s, at %s:%d\n", aStr, + aFilename, aLine); + fputs(msg, stderr); +# else + fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine); +# endif +# 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 +# if defined(MOZ_BUFFER_STDERR) + char msg[1024] = ""; + snprintf(msg, sizeof(msg) - 1, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, + aFilename, aLine); + fputs(msg, stderr); +# else + fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine); +# endif +# if defined(MOZ_DUMP_ASSERTION_STACK) + MozWalkTheStack(stderr, CallerPC(), /* aMaxFrames */ 0); +# endif + fflush(stderr); +#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_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); + MOZ_ASSUME_UNREACHABLE_MARKER(); +} + +# 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 */ \ + MOZ_NOMERGE ::abort(); \ + } while (false) +# else +# define MOZ_REALLY_CRASH(line) \ + do { \ + *((volatile int*)MOZ_CRASH_WRITE_ADDR) = line; /* NOLINT */ \ + MOZ_NOMERGE 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 and early beta + * and MOZ_ASSERT in late Beta and 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_DEBUG_OR_FUZZING is like a MOZ_ASSERT but also enabled in builds + * that are non-DEBUG but FUZZING. This is useful for checks that are too + * expensive for Nightly in general but are still indicating potentially + * critical bugs. + * In fuzzing builds, the assert is rewritten to be a diagnostic assert because + * we already use this in other sensitive places and fuzzing automation is + * set to act on these under all circumstances. + */ +#ifdef FUZZING +# define MOZ_ASSERT_DEBUG_OR_FUZZING(...) MOZ_DIAGNOSTIC_ASSERT(__VA_ARGS__) +#else +# define MOZ_ASSERT_DEBUG_OR_FUZZING(...) MOZ_ASSERT(__VA_ARGS__) +#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_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 early beta 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_BUFFER_STDERR +#undef MOZ_CRASH_CRASHREPORT +#undef MOZ_DUMP_ASSERTION_STACK + +/* + * 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 + +/* + * Provide a fake default value to be used when a value is required but none can + * sensibily be provided without adding undefined behavior or security issues. + * + * This function asserts and aborts if it ever executed. + * + * Example usage: + * + * class Trooper { + * const Droid& lookFor; + * Trooper() : lookFor(MakeCompilerAssumeUnreachableFakeValue< + const Droid&>()) { + * // The class might be instantiated due to existing caller + * // but this never happens in practice. + * } + * }; + * + */ +#ifdef __cplusplus +namespace mozilla { +template <typename T> +static inline T MakeCompilerAssumeUnreachableFakeValue() { + MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE(); +} +} // namespace mozilla +#endif // __cplusplus + +#endif /* mozilla_Assertions_h */ |