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Diffstat (limited to 'mfbt/Assertions.h')
| -rw-r--r-- | mfbt/Assertions.h | 637 |
1 files changed, 637 insertions, 0 deletions
diff --git a/mfbt/Assertions.h b/mfbt/Assertions.h new file mode 100644 index 0000000000..e7b010b7ff --- /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 */ |