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Diffstat (limited to 'mfbt/Assertions.h')
| -rw-r--r-- | mfbt/Assertions.h | 376 |
1 files changed, 376 insertions, 0 deletions
diff --git a/mfbt/Assertions.h b/mfbt/Assertions.h new file mode 100644 index 0000000..407fb24 --- /dev/null +++ b/mfbt/Assertions.h @@ -0,0 +1,376 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* 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 <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*. 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 { ... }; + * MOZ_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. + * + * Be aware of the gcc 4.2 concerns noted further down when writing patches that + * use this macro, particularly if a patch only bounces on OS X. + */ +#ifdef __cplusplus +# if defined(__clang__) +# ifndef __has_extension +# define __has_extension __has_feature /* compatibility, for older versions of clang */ +# endif +# if __has_extension(cxx_static_assert) +# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason) +# endif +# elif defined(__GNUC__) +# if (defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L) && \ + (__GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 3)) +# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason) +# endif +# elif defined(_MSC_VER) +# if _MSC_VER >= 1600 /* MSVC 10 */ +# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason) +# endif +# elif defined(__HP_aCC) +# if __HP_aCC >= 62500 && defined(_HP_CXX0x_SOURCE) +# define MOZ_STATIC_ASSERT(cond, reason) static_assert((cond), reason) +# endif +# endif +#endif +#ifndef MOZ_STATIC_ASSERT +# 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] +# else +# define MOZ_STATIC_ASSERT(cond, reason) \ + extern void MOZ_STATIC_ASSERT_GLUE(moz_static_assert, __LINE__)(int arg[(cond) ? 1 : -1]) +# endif +#endif + +#define MOZ_STATIC_ASSERT_IF(cond, expr, reason) MOZ_STATIC_ASSERT(!(cond) || (expr), reason) + +#ifdef __cplusplus +extern "C" { +#endif + +/* + * MOZ_CRASH 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. + */ +#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. + * + * (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.) + */ +# ifdef __cplusplus +# define MOZ_CRASH() \ + do { \ + __debugbreak(); \ + *((volatile int*) NULL) = 123; \ + ::TerminateProcess(::GetCurrentProcess(), 3); \ + } while (0) +# else +# define MOZ_CRASH() \ + do { \ + __debugbreak(); \ + *((volatile int*) NULL) = 123; \ + TerminateProcess(GetCurrentProcess(), 3); \ + } while (0) +# endif +#else +# ifdef __cplusplus +# define MOZ_CRASH() \ + do { \ + *((volatile int*) NULL) = 123; \ + ::abort(); \ + } while (0) +# else +# define MOZ_CRASH() \ + do { \ + *((volatile int*) NULL) = 123; \ + abort(); \ + } while (0) +# endif +#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 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 +} + +#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". + */ +#ifdef DEBUG + /* First the single-argument form. */ +# define MOZ_ASSERT_HELPER1(expr) \ + do { \ + if (!(expr)) { \ + MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \ + MOZ_CRASH(); \ + } \ + } while (0) + /* Now the two-argument form. */ +# define MOZ_ASSERT_HELPER2(expr, explain) \ + do { \ + if (!(expr)) { \ + MOZ_ReportAssertionFailure(#expr " (" explain ")", __FILE__, __LINE__); \ + MOZ_CRASH(); \ + } \ + } while (0) + /* And now, helper macrology up the wazoo. */ + /* + * Count the number of arguments passed to MOZ_ASSERT, very carefully + * tiptoeing around an MSVC bug where it improperly expands __VA_ARGS__ as a + * single token in argument lists. See these URLs for details: + * + * http://connect.microsoft.com/VisualStudio/feedback/details/380090/variadic-macro-replacement + * http://cplusplus.co.il/2010/07/17/variadic-macro-to-count-number-of-arguments/#comment-644 + */ +# define MOZ_COUNT_ASSERT_ARGS_IMPL2(_1, _2, count, ...) \ + count +# define MOZ_COUNT_ASSERT_ARGS_IMPL(args) \ + MOZ_COUNT_ASSERT_ARGS_IMPL2 args +# define MOZ_COUNT_ASSERT_ARGS(...) \ + MOZ_COUNT_ASSERT_ARGS_IMPL((__VA_ARGS__, 2, 1, 0)) + /* Pick the right helper macro to invoke. */ +# define MOZ_ASSERT_CHOOSE_HELPER2(count) MOZ_ASSERT_HELPER##count +# define MOZ_ASSERT_CHOOSE_HELPER1(count) MOZ_ASSERT_CHOOSE_HELPER2(count) +# define MOZ_ASSERT_CHOOSE_HELPER(count) MOZ_ASSERT_CHOOSE_HELPER1(count) + /* The actual macro. */ +# define MOZ_ASSERT_GLUE(x, y) x y +# define MOZ_ASSERT(...) \ + MOZ_ASSERT_GLUE(MOZ_ASSERT_CHOOSE_HELPER(MOZ_COUNT_ASSERT_ARGS(__VA_ARGS__)), \ + (__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_NOT_REACHED_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_NOT_REACHED, which uses this when + * appropriate. + */ +#if defined(__clang__) +# define MOZ_NOT_REACHED_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 __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 5) +# define MOZ_NOT_REACHED_MARKER() __builtin_unreachable() +# else +# ifdef __cplusplus +# define MOZ_NOT_REACHED_MARKER() ::abort() +# else +# define MOZ_NOT_REACHED_MARKER() abort() +# endif +# endif +#elif defined(_MSC_VER) +# define MOZ_NOT_REACHED_MARKER() __assume(0) +#else +# ifdef __cplusplus +# define MOZ_NOT_REACHED_MARKER() ::abort() +# else +# define MOZ_NOT_REACHED_MARKER() abort() +# endif +#endif + +/* + * MOZ_NOT_REACHED(reason) indicates that the given point can't be reached + * during execution: simply reaching that point in execution is a bug. It takes + * as an argument an error message indicating the reason why that point should + * not have been reachable. + * + * // ...in a language parser... + * void handle(BooleanLiteralNode node) + * { + * if (node.isTrue()) + * handleTrueLiteral(); + * else if (node.isFalse()) + * handleFalseLiteral(); + * else + * MOZ_NOT_REACHED("boolean literal that's not true or false?"); + * } + */ +#if defined(DEBUG) +# define MOZ_NOT_REACHED(reason) \ + do { \ + MOZ_ASSERT(false, reason); \ + MOZ_NOT_REACHED_MARKER(); \ + } while (0) +#else +# define MOZ_NOT_REACHED(reason) MOZ_NOT_REACHED_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_ */ |