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gecko-dev/mfbt/Assertions.h

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/* -*- 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(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API)) && \
!defined(__wasi__)
# define MOZ_DUMP_ASSERTION_STACK
#endif
#if defined(XP_WIN) && (defined(DEBUG) || defined(FUZZING))
# define MOZ_BUFFER_STDERR
#endif
#include "mozilla/Attributes.h"
#include "mozilla/Compiler.h"
#include "mozilla/Fuzzing.h"
#include "mozilla/Likely.h"
#include "mozilla/MacroArgs.h"
#include "mozilla/StaticAnalysisFunctions.h"
#include "mozilla/Types.h"
#ifdef MOZ_DUMP_ASSERTION_STACK
# include "mozilla/StackWalk.h"
#endif
/*
* 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
#if defined(MOZ_HAS_MOZGLUE) || defined(MOZILLA_INTERNAL_API)
static inline void AnnotateMozCrashReason(const char* reason) {
gMozCrashReason = reason;
// See bug 1681846, on 32-bit Android ARM the compiler removes the store to
// gMozCrashReason if this barrier is not present.
asm volatile("" ::: "memory");
}
# define MOZ_CRASH_ANNOTATE(...) AnnotateMozCrashReason(__VA_ARGS__)
#else
# define MOZ_CRASH_ANNOTATE(...) \
do { /* nothing */ \
} while (false)
#endif
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#ifdef _MSC_VER
/*
* 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.
*/
MOZ_BEGIN_EXTERN_C
__declspec(dllimport) int __stdcall TerminateProcess(void* hProcess,
unsigned int uExitCode);
__declspec(dllimport) void* __stdcall GetCurrentProcess(void);
MOZ_END_EXTERN_C
#elif defined(__wasi__)
/*
* On Wasm/WASI platforms, we just call __builtin_trap().
*/
#else
# include <signal.h>
#endif
#ifdef ANDROID
# include <android/log.h>
#endif
MOZ_BEGIN_EXTERN_C
#if defined(ANDROID) && defined(MOZ_DUMP_ASSERTION_STACK)
MOZ_MAYBE_UNUSED static void MOZ_ReportAssertionFailurePrintFrame(
const char* aBuf) {
__android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert", "%s\n", aBuf);
}
#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.
*/
MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_INLINE void
MOZ_ReportAssertionFailure(const char* aStr, const char* aFilename,
int aLine) MOZ_PRETEND_NORETURN_FOR_STATIC_ANALYSIS {
MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_ASSERT", aFilename, aLine, aStr);
#ifdef ANDROID
__android_log_print(ANDROID_LOG_FATAL, "MOZ_Assert",
"Assertion failure: %s, at %s:%d\n", aStr, aFilename,
aLine);
# if defined(MOZ_DUMP_ASSERTION_STACK)
MozWalkTheStackWithWriter(MOZ_ReportAssertionFailurePrintFrame, CallerPC(),
/* aMaxFrames */ 0);
# endif
#else
# if defined(MOZ_BUFFER_STDERR)
char msg[1024] = "";
snprintf(msg, sizeof(msg) - 1, "Assertion failure: %s, at %s:%d\n", aStr,
aFilename, aLine);
fputs(msg, stderr);
# else
fprintf(stderr, "Assertion failure: %s, at %s:%d\n", aStr, aFilename, aLine);
# endif
# if defined(MOZ_DUMP_ASSERTION_STACK)
MozWalkTheStack(stderr, CallerPC(), /* aMaxFrames */ 0);
# endif
fflush(stderr);
#endif
}
MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NEVER_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
# if defined(MOZ_BUFFER_STDERR)
char msg[1024] = "";
snprintf(msg, sizeof(msg) - 1, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr,
aFilename, aLine);
fputs(msg, stderr);
# else
fprintf(stderr, "Hit MOZ_CRASH(%s) at %s:%d\n", aStr, aFilename, aLine);
# endif
# if defined(MOZ_DUMP_ASSERTION_STACK)
MozWalkTheStack(stderr, CallerPC(), /* aMaxFrames */ 0);
# 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 __LINE__ to prevent the compiler from folding multiple crash sites
* together, which would make crash reports hard to understand.
*
* 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.)
*/
MOZ_MAYBE_UNUSED static MOZ_COLD MOZ_NORETURN MOZ_NEVER_INLINE void
MOZ_NoReturn(int aLine) {
*((volatile int*)NULL) = aLine;
TerminateProcess(GetCurrentProcess(), 3);
}
# define MOZ_REALLY_CRASH(line) \
do { \
__debugbreak(); \
MOZ_NoReturn(line); \
} while (false)
#elif __wasi__
# define MOZ_REALLY_CRASH(line) __builtin_trap()
#else
/*
* MOZ_CRASH_WRITE_ADDR is the address to be used when performing a forced
* crash. NULL is preferred however if for some reason NULL cannot be used
* this makes choosing another value possible.
*
* In the case of UBSan certain checks, bounds specifically, cause the compiler
* to emit the 'ud2' instruction when storing to 0x0. This causes forced
* crashes to manifest as ILL (at an arbitrary address) instead of the expected
* SEGV at 0x0.
*/
# ifdef MOZ_UBSAN
# define MOZ_CRASH_WRITE_ADDR 0x1
# else
# define MOZ_CRASH_WRITE_ADDR NULL
# endif
# ifdef __cplusplus
# define MOZ_REALLY_CRASH(line) \
do { \
*((volatile int*)MOZ_CRASH_WRITE_ADDR) = line; /* NOLINT */ \
::abort(); \
} while (false)
# else
# define MOZ_REALLY_CRASH(line) \
do { \
*((volatile int*)MOZ_CRASH_WRITE_ADDR) = line; /* NOLINT */ \
abort(); \
} while (false)
# 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.
*/
#if !(defined(DEBUG) || defined(FUZZING))
# define MOZ_CRASH(...) \
do { \
MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", __FILE__, __LINE__, NULL); \
MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
MOZ_REALLY_CRASH(__LINE__); \
} while (false)
#else
# define MOZ_CRASH(...) \
do { \
MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", __FILE__, __LINE__, NULL); \
MOZ_ReportCrash("" __VA_ARGS__, __FILE__, __LINE__); \
MOZ_CRASH_ANNOTATE("MOZ_CRASH(" __VA_ARGS__ ")"); \
MOZ_REALLY_CRASH(__LINE__); \
} while (false)
#endif
/*
* MOZ_CRASH_UNSAFE(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.
*
* @note This macro causes data collection because crash strings are annotated
* to crash-stats and are publicly visible. Firefox data stewards must do data
* review on usages of this macro.
*/
static MOZ_ALWAYS_INLINE_EVEN_DEBUG MOZ_COLD MOZ_NORETURN void MOZ_Crash(
const char* aFilename, int aLine, const char* aReason) {
MOZ_FUZZING_HANDLE_CRASH_EVENT4("MOZ_CRASH", aFilename, aLine, aReason);
#if defined(DEBUG) || defined(FUZZING)
MOZ_ReportCrash(aReason, aFilename, aLine);
#endif
MOZ_CRASH_ANNOTATE(aReason);
MOZ_REALLY_CRASH(aLine);
}
#define MOZ_CRASH_UNSAFE(reason) MOZ_Crash(__FILE__, __LINE__, reason)
static const size_t sPrintfMaxArgs = 4;
static const size_t sPrintfCrashReasonSize = 1024;
MFBT_API MOZ_COLD MOZ_NEVER_INLINE MOZ_FORMAT_PRINTF(1, 2) const
char* MOZ_CrashPrintf(const char* aFormat, ...);
/*
* 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.
*
* @note This macro causes data collection because crash strings are annotated
* to crash-stats and are publicly visible. Firefox data stewards must do data
* review on usages of this macro.
*/
#define MOZ_CRASH_UNSAFE_PRINTF(format, ...) \
do { \
static_assert(MOZ_ARG_COUNT(__VA_ARGS__) > 0, \
"Did you forget arguments to MOZ_CRASH_UNSAFE_PRINTF? " \
"Or maybe you want MOZ_CRASH instead?"); \
static_assert(MOZ_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_Crash(__FILE__, __LINE__, MOZ_CrashPrintf("" format, __VA_ARGS__)); \
} while (false)
MOZ_END_EXTERN_C
/*
* 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 and early beta
* and MOZ_ASSERT in late Beta and 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.
*
* MOZ_DIAGNOSTIC_ASSERT_ENABLED is defined when MOZ_DIAGNOSTIC_ASSERT is like
* MOZ_RELEASE_ASSERT rather than MOZ_ASSERT.
*/
/*
* 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 <type_traits>
namespace mozilla {
namespace detail {
template <typename T>
struct AssertionConditionType {
using ValueT = std::remove_reference_t<T>;
static_assert(!std::is_array_v<ValueT>,
"Expected boolean assertion condition, got an array or a "
"string!");
static_assert(!std::is_function_v<ValueT>,
"Expected boolean assertion condition, got a function! Did "
"you intend to call that function?");
static_assert(!std::is_floating_point_v<ValueT>,
"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
#if defined(DEBUG) || defined(MOZ_ASAN)
# define MOZ_REPORT_ASSERTION_FAILURE(...) \
MOZ_ReportAssertionFailure(__VA_ARGS__)
#else
# define MOZ_REPORT_ASSERTION_FAILURE(...) \
do { /* nothing */ \
} while (false)
#endif
/* First the single-argument form. */
#define MOZ_ASSERT_HELPER1(kind, expr) \
do { \
MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
MOZ_FUZZING_HANDLE_CRASH_EVENT2(kind, #expr); \
MOZ_REPORT_ASSERTION_FAILURE(#expr, __FILE__, __LINE__); \
MOZ_CRASH_ANNOTATE(kind "(" #expr ")"); \
MOZ_REALLY_CRASH(__LINE__); \
} \
} while (false)
/* Now the two-argument form. */
#define MOZ_ASSERT_HELPER2(kind, expr, explain) \
do { \
MOZ_VALIDATE_ASSERT_CONDITION_TYPE(expr); \
if (MOZ_UNLIKELY(!MOZ_CHECK_ASSERT_ASSIGNMENT(expr))) { \
MOZ_FUZZING_HANDLE_CRASH_EVENT2(kind, #expr); \
MOZ_REPORT_ASSERTION_FAILURE(#expr " (" explain ")", __FILE__, \
__LINE__); \
MOZ_CRASH_ANNOTATE(kind "(" #expr ") (" explain ")"); \
MOZ_REALLY_CRASH(__LINE__); \
} \
} while (false)
#define MOZ_ASSERT_GLUE(a, b) a b
#define MOZ_RELEASE_ASSERT(...) \
MOZ_ASSERT_GLUE( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
("MOZ_RELEASE_ASSERT", __VA_ARGS__))
#ifdef DEBUG
# define MOZ_ASSERT(...) \
MOZ_ASSERT_GLUE( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
("MOZ_ASSERT", __VA_ARGS__))
#else
# define MOZ_ASSERT(...) \
do { \
} while (false)
#endif /* DEBUG */
#if defined(MOZ_DIAGNOSTIC_ASSERT_ENABLED)
# define MOZ_DIAGNOSTIC_ASSERT(...) \
MOZ_ASSERT_GLUE( \
MOZ_PASTE_PREFIX_AND_ARG_COUNT(MOZ_ASSERT_HELPER, __VA_ARGS__), \
("MOZ_DIAGNOSTIC_ASSERT", __VA_ARGS__))
#else
# define MOZ_DIAGNOSTIC_ASSERT(...) \
do { \
} while (false)
#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 (false)
#else
# define MOZ_ASSERT_IF(cond, expr) \
do { \
} while (false)
#endif
/*
* MOZ_DIAGNOSTIC_ASSERT_IF is like MOZ_ASSERT_IF, but using
* MOZ_DIAGNOSTIC_ASSERT as the underlying assert.
*
* See the block comment for MOZ_DIAGNOSTIC_ASSERT above for more details on how
* diagnostic assertions work and how to use them.
*/
#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
# define MOZ_DIAGNOSTIC_ASSERT_IF(cond, expr) \
do { \
if (cond) { \
MOZ_DIAGNOSTIC_ASSERT(expr); \
} \
} while (false)
#else
# define MOZ_DIAGNOSTIC_ASSERT_IF(cond, expr) \
do { \
} while (false)
#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 (false)
/**
* 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 [[fallthrough]]? In
* release builds, the MOZ_ASSERT(false) will expand to `do { } while (false)`,
* requiring a [[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 [[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!
* [[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(...) \
MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " __VA_ARGS__)
#else
# define MOZ_FALLTHROUGH_ASSERT(...) [[fallthrough]]
#endif
/*
* MOZ_ALWAYS_TRUE(expr) and friends always evaluate the provided expression,
* in debug builds and in release builds both. Then, in debug builds and
* Nightly and early beta builds, the value of the expression is
* asserted either true or false using MOZ_DIAGNOSTIC_ASSERT.
*/
#define MOZ_ALWAYS_TRUE(expr) \
do { \
if (MOZ_LIKELY(expr)) { \
/* Silence [[nodiscard]]. */ \
} else { \
MOZ_DIAGNOSTIC_ASSERT(false, #expr); \
} \
} while (false)
#define MOZ_ALWAYS_FALSE(expr) MOZ_ALWAYS_TRUE(!(expr))
#define MOZ_ALWAYS_OK(expr) MOZ_ALWAYS_TRUE((expr).isOk())
#define MOZ_ALWAYS_ERR(expr) MOZ_ALWAYS_TRUE((expr).isErr())
/*
* These are disabled when fuzzing
*/
#ifdef FUZZING
# define MOZ_CRASH_UNLESS_FUZZING(...) \
do { \
} while (0)
# define MOZ_ASSERT_UNLESS_FUZZING(...) \
do { \
} while (0)
#else
# define MOZ_CRASH_UNLESS_FUZZING(...) MOZ_CRASH(__VA_ARGS__)
# define MOZ_ASSERT_UNLESS_FUZZING(...) MOZ_ASSERT(__VA_ARGS__)
#endif
#undef MOZ_BUFFER_STDERR
#undef MOZ_CRASH_CRASHREPORT
#undef MOZ_DUMP_ASSERTION_STACK
/*
* This is only used by Array and nsTArray classes, therefore it is not
* required when included from C code.
*/
#ifdef __cplusplus
namespace mozilla::detail {
MFBT_API MOZ_NORETURN MOZ_COLD void InvalidArrayIndex_CRASH(size_t aIndex,
size_t aLength);
} // namespace mozilla::detail
#endif // __cplusplus
/*
* Provide a fake default value to be used when a value is required but none can
* sensibily be provided without adding undefined behavior or security issues.
*
* This function asserts and aborts if it ever executed.
*
* Example usage:
*
* class Trooper {
* const Droid& lookFor;
* Trooper() : lookFor(MakeCompilerAssumeUnreachableFakeValue<
const Droid&>()) {
* // The class might be instantiated due to existing caller
* // but this never happens in practice.
* }
* };
*
*/
#ifdef __cplusplus
namespace mozilla {
template <typename T>
static inline T MakeCompilerAssumeUnreachableFakeValue() {
MOZ_MAKE_COMPILER_ASSUME_IS_UNREACHABLE();
}
} // namespace mozilla
#endif // __cplusplus
#endif /* mozilla_Assertions_h */
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