/* -*- 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. */ /* * Implement MOZ_VALIDATE_ASSERT_CONDITION_TYPE, which is used to guard against * accidentally passing something unintended in lieu of an assertion condition. */ #ifdef __cplusplus # if defined(__clang__) # define MOZ_SUPPORT_ASSERT_CONDITION_TYPE_VALIDATION # elif defined(__GNUC__) // B2G GCC 4.4 has insufficient decltype support. # if MOZ_GCC_VERSION_AT_LEAST(4, 5, 0) # define MOZ_SUPPORT_ASSERT_CONDITION_TYPE_VALIDATION # endif # elif defined(_MSC_VER) // Disabled for now because of insufficient decltype support. Bug 1004028. # endif #endif #ifdef MOZ_SUPPORT_ASSERT_CONDITION_TYPE_VALIDATION # include "mozilla/TypeTraits.h" namespace mozilla { namespace detail { template struct IsFunction { static const bool value = false; }; template struct IsFunction { static const bool value = true; }; template void ValidateAssertConditionType() { typedef typename RemoveReference::Type ValueT; static_assert(!IsArray::value, "Expected boolean assertion condition, got an array or a string!"); static_assert(!IsFunction::value, "Expected boolean assertion condition, got a function! Did you intend to call that function?"); static_assert(!IsFloatingPoint::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."); } } // namespace detail } // namespace mozilla # define MOZ_VALIDATE_ASSERT_CONDITION_TYPE(x) mozilla::detail::ValidateAssertConditionType() #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(!(expr))) { \ MOZ_ReportAssertionFailure(#expr, __FILE__, __LINE__); \ MOZ_REALLY_CRASH(); \ } \ } while (0) /* Now the two-argument form. */ #define MOZ_ASSERT_HELPER2(expr, explain) \ do { \ MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \ 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 */