// Copyright (c) 2013, Kenton Varda <temporal@gmail.com> // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions are met: // // 1. Redistributions of source code must retain the above copyright notice, this // list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright notice, // this list of conditions and the following disclaimer in the documentation // and/or other materials provided with the distribution. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND // ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED // WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE // DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR // ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES // (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; // LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND // ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS // SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. // This file declares convenient macros for debug logging and error handling. The macros make // it excessively easy to extract useful context information from code. Example: // // KJ_ASSERT(a == b, a, b, "a and b must be the same."); // // On failure, this will throw an exception whose description looks like: // // myfile.c++:43: bug in code: expected a == b; a = 14; b = 72; a and b must be the same. // // As you can see, all arguments after the first provide additional context. // // The macros available are: // // * `KJ_LOG(severity, ...)`: Just writes a log message, to stderr by default (but you can // intercept messages by implementing an ExceptionCallback). `severity` is `INFO`, `WARNING`, // `ERROR`, or `FATAL`. By default, `INFO` logs are not written, but for command-line apps the // user should be able to pass a flag like `--verbose` to enable them. Other log levels are // enabled by default. Log messages -- like exceptions -- can be intercepted by registering an // ExceptionCallback. // // * `KJ_DBG(...)`: Like `KJ_LOG`, but intended specifically for temporary log lines added while // debugging a particular problem. Calls to `KJ_DBG` should always be deleted before committing // code. It is suggested that you set up a pre-commit hook that checks for this. // // * `KJ_ASSERT(condition, ...)`: Throws an exception if `condition` is false, or aborts if // exceptions are disabled. This macro should be used to check for bugs in the surrounding code // and its dependencies, but NOT to check for invalid input. The macro may be followed by a // brace-delimited code block; if so, the block will be executed in the case where the assertion // fails, before throwing the exception. If control jumps out of the block (e.g. with "break", // "return", or "goto"), then the error is considered "recoverable" -- in this case, if // exceptions are disabled, execution will continue normally rather than aborting (but if // exceptions are enabled, an exception will still be thrown on exiting the block). A "break" // statement in particular will jump to the code immediately after the block (it does not break // any surrounding loop or switch). Example: // // KJ_ASSERT(value >= 0, "Value cannot be negative.", value) { // // Assertion failed. Set value to zero to "recover". // value = 0; // // Don't abort if exceptions are disabled. Continue normally. // // (Still throw an exception if they are enabled, though.) // break; // } // // When exceptions are disabled, we'll get here even if the assertion fails. // // Otherwise, we get here only if the assertion passes. // // * `KJ_REQUIRE(condition, ...)`: Like `KJ_ASSERT` but used to check preconditions -- e.g. to // validate parameters passed from a caller. A failure indicates that the caller is buggy. // // * `KJ_SYSCALL(code, ...)`: Executes `code` assuming it makes a system call. A negative result // is considered an error, with error code reported via `errno`. EINTR is handled by retrying. // Other errors are handled by throwing an exception. If you need to examine the return code, // assign it to a variable like so: // // int fd; // KJ_SYSCALL(fd = open(filename, O_RDONLY), filename); // // `KJ_SYSCALL` can be followed by a recovery block, just like `KJ_ASSERT`. // // * `KJ_NONBLOCKING_SYSCALL(code, ...)`: Like KJ_SYSCALL, but will not throw an exception on // EAGAIN/EWOULDBLOCK. The calling code should check the syscall's return value to see if it // indicates an error; in this case, it can assume the error was EAGAIN because any other error // would have caused an exception to be thrown. // // * `KJ_CONTEXT(...)`: Notes additional contextual information relevant to any exceptions thrown // from within the current scope. That is, until control exits the block in which KJ_CONTEXT() // is used, if any exception is generated, it will contain the given information in its context // chain. This is helpful because it can otherwise be very difficult to come up with error // messages that make sense within low-level helper code. Note that the parameters to // KJ_CONTEXT() are only evaluated if an exception is thrown. This implies that any variables // used must remain valid until the end of the scope. // // Notes: // * Do not write expressions with side-effects in the message content part of the macro, as the // message will not necessarily be evaluated. // * For every macro `FOO` above except `LOG`, there is also a `FAIL_FOO` macro used to report // failures that already happened. For the macros that check a boolean condition, `FAIL_FOO` // omits the first parameter and behaves like it was `false`. `FAIL_SYSCALL` and // `FAIL_RECOVERABLE_SYSCALL` take a string and an OS error number as the first two parameters. // The string should be the name of the failed system call. // * For every macro `FOO` above, there is a `DFOO` version (or `RECOVERABLE_DFOO`) which is only // executed in debug mode, i.e. when KJ_DEBUG is defined. KJ_DEBUG is defined automatically // by common.h when compiling without optimization (unless NDEBUG is defined), but you can also // define it explicitly (e.g. -DKJ_DEBUG). Generally, production builds should NOT use KJ_DEBUG // as it may enable expensive checks that are unlikely to fail. #ifndef KJ_DEBUG_H_ #define KJ_DEBUG_H_ #include "string.h" #include "exception.h" namespace kj { #define KJ_LOG(severity, ...) \ if (!::kj::_::Debug::shouldLog(::kj::_::Debug::Severity::severity)) {} else \ ::kj::_::Debug::log(__FILE__, __LINE__, ::kj::_::Debug::Severity::severity, \ #__VA_ARGS__, __VA_ARGS__) #define KJ_DBG(...) KJ_LOG(DBG, ##__VA_ARGS__) #define _kJ_FAULT(nature, cond, ...) \ if (KJ_LIKELY(cond)) {} else \ for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Nature::nature, 0, \ #cond, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal()) #define _kJ_FAIL_FAULT(nature, ...) \ for (::kj::_::Debug::Fault f(__FILE__, __LINE__, ::kj::Exception::Nature::nature, 0, \ nullptr, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal()) #define KJ_ASSERT(...) _kJ_FAULT(LOCAL_BUG, ##__VA_ARGS__) #define KJ_REQUIRE(...) _kJ_FAULT(PRECONDITION, ##__VA_ARGS__) #define KJ_FAIL_ASSERT(...) _kJ_FAIL_FAULT(LOCAL_BUG, ##__VA_ARGS__) #define KJ_FAIL_REQUIRE(...) _kJ_FAIL_FAULT(PRECONDITION, ##__VA_ARGS__) #define KJ_SYSCALL(call, ...) \ if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, false)) {} else \ for (::kj::_::Debug::Fault f( \ __FILE__, __LINE__, ::kj::Exception::Nature::OS_ERROR, \ _kjSyscallResult.getErrorNumber(), #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal()) #define KJ_NONBLOCKING_SYSCALL(call, ...) \ if (auto _kjSyscallResult = ::kj::_::Debug::syscall([&](){return (call);}, true)) {} else \ for (::kj::_::Debug::Fault f( \ __FILE__, __LINE__, ::kj::Exception::Nature::OS_ERROR, \ _kjSyscallResult.getErrorNumber(), #call, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal()) #define KJ_FAIL_SYSCALL(code, errorNumber, ...) \ for (::kj::_::Debug::Fault f( \ __FILE__, __LINE__, ::kj::Exception::Nature::OS_ERROR, \ errorNumber, code, #__VA_ARGS__, ##__VA_ARGS__);; f.fatal()) #define KJ_CONTEXT(...) \ auto KJ_UNIQUE_NAME(_kjContextFunc) = [&]() -> ::kj::_::Debug::Context::Value { \ return ::kj::_::Debug::Context::Value(__FILE__, __LINE__, \ ::kj::_::Debug::makeContextDescription(#__VA_ARGS__, ##__VA_ARGS__)); \ }; \ ::kj::_::Debug::ContextImpl<decltype(KJ_UNIQUE_NAME(_kjContextFunc))> \ KJ_UNIQUE_NAME(_kjContext)(KJ_UNIQUE_NAME(_kjContextFunc)) #define _kJ_NONNULL(nature, value, ...) \ (*({ \ auto _kj_result = ::kj::_::readMaybe(value); \ if (KJ_UNLIKELY(!_kj_result)) { \ ::kj::_::Debug::Fault(__FILE__, __LINE__, ::kj::Exception::Nature::nature, 0, \ #value " != nullptr", #__VA_ARGS__, ##__VA_ARGS__).fatal(); \ } \ _kj_result; \ })) #define KJ_ASSERT_NONNULL(value, ...) _kJ_NONNULL(LOCAL_BUG, value, ##__VA_ARGS__) #define KJ_REQUIRE_NONNULL(value, ...) _kJ_NONNULL(PRECONDITION, value, ##__VA_ARGS__) #ifdef KJ_DEBUG #define KJ_DLOG LOG #define KJ_DASSERT KJ_ASSERT #define KJ_DREQUIRE KJ_REQUIRE #else #define KJ_DLOG(...) do {} while (false) #define KJ_DASSERT(...) do {} while (false) #define KJ_DREQUIRE(...) do {} while (false) #endif namespace _ { // private class Debug { public: Debug() = delete; enum class Severity { INFO, // Information describing what the code is up to, which users may request to see // with a flag like `--verbose`. Does not indicate a problem. Not printed by // default; you must call setLogLevel(INFO) to enable. WARNING, // A problem was detected but execution can continue with correct output. ERROR, // Something is wrong, but execution can continue with garbage output. FATAL, // Something went wrong, and execution cannot continue. DBG // Temporary debug logging. See KJ_DBG. // Make sure to update the stringifier if you add a new severity level. }; static inline bool shouldLog(Severity severity) { return severity >= minSeverity; } // Returns whether messages of the given severity should be logged. static inline void setLogLevel(Severity severity) { minSeverity = severity; } // Set the minimum message severity which will be logged. // // TODO(someday): Expose publicly. template <typename... Params> static void log(const char* file, int line, Severity severity, const char* macroArgs, Params&&... params); class Fault { public: template <typename... Params> Fault(const char* file, int line, Exception::Nature nature, int errorNumber, const char* condition, const char* macroArgs, Params&&... params); ~Fault() noexcept(false); void fatal() KJ_NORETURN; // Throw the exception. private: void init(const char* file, int line, Exception::Nature nature, int errorNumber, const char* condition, const char* macroArgs, ArrayPtr<String> argValues); Exception* exception; }; class SyscallResult { public: inline SyscallResult(int errorNumber): errorNumber(errorNumber) {} inline operator void*() { return errorNumber == 0 ? this : nullptr; } inline int getErrorNumber() { return errorNumber; } private: int errorNumber; }; template <typename Call> static SyscallResult syscall(Call&& call, bool nonblocking); class Context: public ExceptionCallback { public: Context(); KJ_DISALLOW_COPY(Context); virtual ~Context() noexcept(false); struct Value { const char* file; int line; String description; inline Value(const char* file, int line, String&& description) : file(file), line(line), description(mv(description)) {} }; virtual Value evaluate() = 0; virtual void onRecoverableException(Exception&& exception) override; virtual void onFatalException(Exception&& exception) override; virtual void logMessage(const char* file, int line, int contextDepth, String&& text) override; private: bool logged; Maybe<Value> value; Value ensureInitialized(); }; template <typename Func> class ContextImpl: public Context { public: inline ContextImpl(Func& func): func(func) {} KJ_DISALLOW_COPY(ContextImpl); Value evaluate() override { return func(); } private: Func& func; }; template <typename... Params> static String makeContextDescription(const char* macroArgs, Params&&... params); private: static Severity minSeverity; static void logInternal(const char* file, int line, Severity severity, const char* macroArgs, ArrayPtr<String> argValues); static String makeContextDescriptionInternal(const char* macroArgs, ArrayPtr<String> argValues); static int getOsErrorNumber(bool nonblocking); // Get the error code of the last error (e.g. from errno). Returns -1 on EINTR. }; ArrayPtr<const char> KJ_STRINGIFY(Debug::Severity severity); template <typename... Params> void Debug::log(const char* file, int line, Severity severity, const char* macroArgs, Params&&... params) { String argValues[sizeof...(Params)] = {str(params)...}; logInternal(file, line, severity, macroArgs, arrayPtr(argValues, sizeof...(Params))); } template <typename... Params> Debug::Fault::Fault(const char* file, int line, Exception::Nature nature, int errorNumber, const char* condition, const char* macroArgs, Params&&... params) : exception(nullptr) { String argValues[sizeof...(Params)] = {str(params)...}; init(file, line, nature, errorNumber, condition, macroArgs, arrayPtr(argValues, sizeof...(Params))); } template <typename Call> Debug::SyscallResult Debug::syscall(Call&& call, bool nonblocking) { while (call() < 0) { int errorNum = getOsErrorNumber(nonblocking); // getOsErrorNumber() returns -1 to indicate EINTR. // Also, if nonblocking is true, then it returns 0 on EAGAIN, which will then be treated as a // non-error. if (errorNum != -1) { return SyscallResult(errorNum); } } return SyscallResult(0); } template <typename... Params> String Debug::makeContextDescription(const char* macroArgs, Params&&... params) { String argValues[sizeof...(Params)] = {str(params)...}; return makeContextDescriptionInternal(macroArgs, arrayPtr(argValues, sizeof...(Params))); } } // namespace _ (private) } // namespace kj #endif // KJ_DEBUG_H_