diff -r 000000000000 -r 6474c204b198 mfbt/Assertions.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/mfbt/Assertions.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,428 @@ +/* -*- 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 + +#include "mozilla/Attributes.h" +#include "mozilla/Compiler.h" +#include "mozilla/Likely.h" +#include "mozilla/MacroArgs.h" + +#include +#include +#include +#ifdef WIN32 + /* + * TerminateProcess and GetCurrentProcess are defined in , which + * further depends on . 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 +#endif +#ifdef ANDROID +# include +#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 |s| as an assertion failure (using file and ln 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_ALWAYS_INLINE void +MOZ_ReportAssertionFailure(const char* s, const char* file, int ln) +{ +#ifdef ANDROID + __android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert", + "Assertion failure: %s, at %s:%d\n", s, file, ln); +#else + fprintf(stderr, "Assertion failure: %s, at %s:%d\n", s, file, ln); + fflush(stderr); +#endif +} + +static MOZ_ALWAYS_INLINE void +MOZ_ReportCrash(const char* s, const char* file, int ln) +{ +#ifdef ANDROID + __android_log_print(ANDROID_LOG_FATAL, "MOZ_CRASH", + "Hit MOZ_CRASH(%s) at %s:%d\n", s, file, ln); +#else + fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", s, file, ln); + 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() \ + do { \ + ::__debugbreak(); \ + *((volatile int*) NULL) = 123; \ + ::TerminateProcess(::GetCurrentProcess(), 3); \ + ::MOZ_NoReturn(); \ + } while (0) +# else +# define MOZ_REALLY_CRASH() \ + do { \ + __debugbreak(); \ + *((volatile int*) NULL) = 123; \ + TerminateProcess(GetCurrentProcess(), 3); \ + MOZ_NoReturn(); \ + } while (0) +# endif +#else +# ifdef __cplusplus +# define MOZ_REALLY_CRASH() \ + do { \ + *((volatile int*) NULL) = 123; \ + ::abort(); \ + } while (0) +# else +# define MOZ_REALLY_CRASH() \ + do { \ + *((volatile int*) NULL) = 123; \ + 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(...) MOZ_REALLY_CRASH() +#else +# define MOZ_CRASH(...) \ + do { \ + MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \ + MOZ_REALLY_CRASH(); \ + } while(0) +#endif + +#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 and , 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. + */ + +/* First the single-argument form. */ +#define MOZ_ASSERT_HELPER1(expr) \ + do { \ + if (MOZ_UNLIKELY(!(expr))) { \ + MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \ + MOZ_REALLY_CRASH(); \ + } \ + } while (0) +/* Now the two-argument form. */ +#define MOZ_ASSERT_HELPER2(expr, explain) \ + do { \ + if (MOZ_UNLIKELY(!(expr))) { \ + MOZ_ReportAssertionFailure(#expr " (" explain ")", __FILE__, __LINE__); \ + MOZ_REALLY_CRASH(); \ + } \ + } 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 */ + +/* + * 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 + * probably use the higher level MOZ_ASSUME_UNREACHABLE, which uses this when + * appropriate. + */ +#if defined(__clang__) +# define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable() +#elif defined(__GNUC__) + /* + * __builtin_unreachable() was implemented in gcc 4.5. If we don't have + * that, call a noreturn function; abort() will do nicely. Qualify the call + * in C++ in case there's another abort() visible in local scope. + */ +# if MOZ_GCC_VERSION_AT_LEAST(4, 5, 0) +# define MOZ_ASSUME_UNREACHABLE_MARKER() __builtin_unreachable() +# else +# ifdef __cplusplus +# define MOZ_ASSUME_UNREACHABLE_MARKER() ::abort() +# else +# define MOZ_ASSUME_UNREACHABLE_MARKER() abort() +# endif +# endif +#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_ASSUME_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_ASSUME_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_ASSUME_UNREACHABLE more widely. + * + * Note that MOZ_ASSUME_UNREACHABLE is noreturn, so it's valid not to return a + * value following a MOZ_ASSUME_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_ASSUME_UNREACHABLE("can only handle VALUE_INT and VALUE_FLOAT"); + * } + * } + */ +#if defined(DEBUG) +# define MOZ_ASSUME_UNREACHABLE(...) \ + do { \ + MOZ_ASSERT(false, "MOZ_ASSUME_UNREACHABLE(" __VA_ARGS__ ")"); \ + MOZ_ASSUME_UNREACHABLE_MARKER(); \ + } while (0) +#else +# define MOZ_ASSUME_UNREACHABLE(reason) MOZ_ASSUME_UNREACHABLE_MARKER() +#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) MOZ_ASSERT((expr)) +# define MOZ_ALWAYS_FALSE(expr) MOZ_ASSERT(!(expr)) +#else +# define MOZ_ALWAYS_TRUE(expr) ((void)(expr)) +# define MOZ_ALWAYS_FALSE(expr) ((void)(expr)) +#endif + +#endif /* mozilla_Assertions_h */