/* -*- 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 "mozilla/Compiler.h" #include "mozilla/Likely.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*. 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) # 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 /* * 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 #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 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". */ #ifdef DEBUG /* First the single-argument form. */ # define MOZ_ASSERT_HELPER1(expr) \ do { \ if (MOZ_UNLIKELY(!(expr))) { \ MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \ MOZ_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_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 MOZ_GCC_VERSION_AT_LEAST(4, 5, 0) # 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_ */