forked from mirrors/gecko-dev
322 lines
11 KiB
C++
322 lines
11 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef mozilla_logging_h
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#define mozilla_logging_h
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stdarg.h>
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#include "mozilla/Assertions.h"
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#include "mozilla/Atomics.h"
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#include "mozilla/Attributes.h"
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#include "mozilla/Likely.h"
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// We normally have logging enabled everywhere, but measurements showed that
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// having logging enabled on Android is quite expensive (hundreds of kilobytes
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// for both the format strings for logging and the code to perform all the
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// logging calls). Because retrieving logs from a mobile device is
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// comparatively more difficult for Android than it is for desktop and because
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// desktop machines tend to be less space/bandwidth-constrained than Android
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// devices, we've chosen to leave logging enabled on desktop, but disabled on
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// Android. Given that logging can still be useful for development purposes,
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// however, we leave logging enabled on Android developer builds.
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#if !defined(ANDROID) || !defined(RELEASE_OR_BETA)
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# define MOZ_LOGGING_ENABLED 1
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#else
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# define MOZ_LOGGING_ENABLED 0
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#endif
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// The mandatory extension we add to log files. Note that rotate will append
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// the file piece number still at the end.
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#define MOZ_LOG_FILE_EXTENSION ".moz_log"
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// Token for Process ID substitution.
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#define MOZ_LOG_PID_TOKEN "%PID"
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namespace mozilla {
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class TimeStamp;
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// While not a 100% mapping to PR_LOG's numeric values, mozilla::LogLevel does
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// maintain a direct mapping for the Disabled, Debug and Verbose levels.
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//
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// Mappings of LogLevel to PR_LOG's numeric values:
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//
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// +---------+------------------+-----------------+
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// | Numeric | NSPR Logging | Mozilla Logging |
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// +---------+------------------+-----------------+
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// | 0 | PR_LOG_NONE | Disabled |
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// | 1 | PR_LOG_ALWAYS | Error |
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// | 2 | PR_LOG_ERROR | Warning |
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// | 3 | PR_LOG_WARNING | Info |
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// | 4 | PR_LOG_DEBUG | Debug |
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// | 5 | PR_LOG_DEBUG + 1 | Verbose |
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// +---------+------------------+-----------------+
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//
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enum class LogLevel {
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Disabled = 0,
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Error,
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Warning,
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Info,
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Debug,
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Verbose,
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};
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/**
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* Safely converts an integer into a valid LogLevel.
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*/
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LogLevel ToLogLevel(int32_t aLevel);
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class LogModule {
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public:
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~LogModule() { ::free(mName); }
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/**
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* Retrieves the module with the given name. If it does not already exist
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* it will be created.
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*
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* @param aName The name of the module.
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* @return A log module for the given name. This may be shared.
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*/
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static LogModule* Get(const char* aName);
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/**
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* Logging processes -MOZ_LOG and -MOZ_LOG_FILE command line arguments
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* to override or set modules and the file as if passed through MOZ_LOG
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* and MOZ_LOG_FILE env vars. It's fine to pass (0, nullptr) if args
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* are not accessible in the caller's context, it will just do nothing.
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* Note that the args take effect (are processed) only when this function
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* is called the first time.
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*/
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static void Init(int argc, char* argv[]);
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/**
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* Sets the log file to the given filename.
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*/
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static void SetLogFile(const char* aFilename);
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/**
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* @param aBuffer - pointer to a buffer
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* @param aLength - the length of the buffer
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*
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* @return the actual length of the filepath.
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*/
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static uint32_t GetLogFile(char* aBuffer, size_t aLength);
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/**
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* @param aAddTimestamp If we should log a time stamp with every message.
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*/
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static void SetAddTimestamp(bool aAddTimestamp);
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/**
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* @param aIsSync If we should flush the file after every logged message.
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*/
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static void SetIsSync(bool aIsSync);
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/**
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* @param aCaptureStacks If we should capture stacks for the Firefox
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* Profiler markers that are recorded for for each log entry.
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*/
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static void SetCaptureStacks(bool aCaptureStacks);
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/**
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* Indicates whether or not the given log level is enabled.
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*/
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bool ShouldLog(LogLevel aLevel) const { return mLevel >= aLevel; }
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/**
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* Retrieves the log module's current level.
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*/
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LogLevel Level() const { return mLevel; }
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/**
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* Sets the log module's level.
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*/
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void SetLevel(LogLevel level);
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/**
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* Print a log message for this module.
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*/
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void Printv(LogLevel aLevel, const char* aFmt, va_list aArgs) const
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MOZ_FORMAT_PRINTF(3, 0);
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void Printv(LogLevel aLevel, const TimeStamp* aStart, const char* aFmt,
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va_list aArgs) const MOZ_FORMAT_PRINTF(4, 0);
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/**
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* Retrieves the module name.
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*/
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const char* Name() const { return mName; }
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private:
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friend class LogModuleManager;
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explicit LogModule(const char* aName, LogLevel aLevel)
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: mName(strdup(aName)), mLevel(aLevel) {}
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LogModule(LogModule&) = delete;
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LogModule& operator=(const LogModule&) = delete;
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char* mName;
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Atomic<LogLevel, Relaxed> mLevel;
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};
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/**
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* Helper class that lazy loads the given log module. This is safe to use for
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* declaring static references to log modules and can be used as a replacement
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* for accessing a LogModule directly.
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*
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* Example usage:
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* static LazyLogModule sLayoutLog("layout");
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*
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* void Foo() {
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* MOZ_LOG(sLayoutLog, LogLevel::Verbose, ("Entering foo"));
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* }
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*/
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class LazyLogModule final {
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public:
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explicit constexpr LazyLogModule(const char* aLogName)
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: mLogName(aLogName), mLog(nullptr) {}
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MOZ_NEVER_INLINE_DEBUG operator LogModule*() {
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// NB: The use of an atomic makes the reading and assignment of mLog
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// thread-safe. There is a small chance that mLog will be set more
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// than once, but that's okay as it will be set to the same LogModule
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// instance each time. Also note LogModule::Get is thread-safe.
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LogModule* tmp = mLog;
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if (MOZ_UNLIKELY(!tmp)) {
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tmp = LogModule::Get(mLogName);
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mLog = tmp;
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}
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return tmp;
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}
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private:
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const char* const mLogName;
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Atomic<LogModule*, ReleaseAcquire> mLog;
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};
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namespace detail {
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inline bool log_test(const LogModule* module, LogLevel level) {
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MOZ_ASSERT(level != LogLevel::Disabled);
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return module && module->ShouldLog(level);
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}
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void log_print(const LogModule* aModule, LogLevel aLevel, const char* aFmt, ...)
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MOZ_FORMAT_PRINTF(3, 4);
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void log_print(const LogModule* aModule, LogLevel aLevel, TimeStamp* aStart,
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const char* aFmt, ...) MOZ_FORMAT_PRINTF(4, 5);
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} // namespace detail
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} // namespace mozilla
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// Helper macro used convert MOZ_LOG's third parameter, |_args|, from a
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// parenthesized form to a varargs form. For example:
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// ("%s", "a message") => "%s", "a message"
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#define MOZ_LOG_EXPAND_ARGS(...) __VA_ARGS__
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#if MOZ_LOGGING_ENABLED
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# define MOZ_LOG_TEST(_module, _level) \
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MOZ_UNLIKELY(mozilla::detail::log_test(_module, _level))
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#else
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// Define away MOZ_LOG_TEST here so the compiler will fold away entire
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// logging blocks via dead code elimination, e.g.:
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//
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// if (MOZ_LOG_TEST(...)) {
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// ...compute things to log and log them...
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// }
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# define MOZ_LOG_TEST(_module, _level) false
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#endif
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// The natural definition of the MOZ_LOG macro would expand to:
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//
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// do {
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// if (MOZ_LOG_TEST(_module, _level)) {
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// mozilla::detail::log_print(_module, ...);
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// }
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// } while (0)
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//
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// However, since _module is a LazyLogModule, and we need to call
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// LazyLogModule::operator() to get a LogModule* for the MOZ_LOG_TEST
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// macro and for the logging call, we'll wind up doing *two* calls, one
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// for each, rather than a single call. The compiler is not able to
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// fold the two calls into one, and the extra call can have a
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// significant effect on code size. (Making LazyLogModule::operator() a
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// `const` function does not have any effect.)
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//
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// Therefore, we will have to make a single call ourselves. But again,
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// the natural definition:
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//
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// do {
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// ::mozilla::LogModule* real_module = _module;
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// if (MOZ_LOG_TEST(real_module, _level)) {
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// mozilla::detail::log_print(real_module, ...);
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// }
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// } while (0)
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//
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// also has a problem: if logging is disabled, then we will call
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// LazyLogModule::operator() unnecessarily, and the compiler will not be
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// able to optimize away the call as dead code. We would like to avoid
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// such a scenario, as the whole point of disabling logging is for the
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// logging statements to not generate any code.
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//
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// Therefore, we need different definitions of MOZ_LOG, depending on
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// whether logging is enabled or not. (We need an actual definition of
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// MOZ_LOG even when logging is disabled to ensure the compiler sees that
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// variables only used during logging code are actually used, even if the
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// code will never be executed.) Hence, the following code.
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//
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// MOZ_LOG_DURATION takes a start time, and will generate a time range
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// in the logs. Also, if the Firefox Profiler is running,
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// MOZ_LOG_DURATION will generate a marker with a time duration
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// instead of a single point in time.
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#if MOZ_LOGGING_ENABLED
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# define MOZ_LOG(_module, _level, _args) \
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do { \
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const ::mozilla::LogModule* moz_real_module = _module; \
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if (MOZ_LOG_TEST(moz_real_module, _level)) { \
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mozilla::detail::log_print(moz_real_module, _level, \
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MOZ_LOG_EXPAND_ARGS _args); \
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} \
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} while (0)
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# define MOZ_LOG_DURATION(_module, _level, start, _args) \
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do { \
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const ::mozilla::LogModule* moz_real_module = _module; \
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if (MOZ_LOG_TEST(moz_real_module, _level)) { \
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mozilla::detail::log_print(moz_real_module, _level, start, \
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MOZ_LOG_EXPAND_ARGS _args); \
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} \
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} while (0)
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#else
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# define MOZ_LOG(_module, _level, _args) \
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do { \
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if (MOZ_LOG_TEST(_module, _level)) { \
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mozilla::detail::log_print(_module, _level, \
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MOZ_LOG_EXPAND_ARGS _args); \
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} \
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} while (0)
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# define MOZ_LOG_DURATION(_module, _level, start, _args) \
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do { \
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if (MOZ_LOG_TEST(_module, _level)) { \
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mozilla::detail::log_print(_module, _level, start, \
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MOZ_LOG_EXPAND_ARGS _args); \
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} \
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} while (0)
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#endif
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// This #define is a Logging.h-only knob! Don't encourage people to get fancy
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// with their log definitions by exporting it outside of Logging.h.
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#undef MOZ_LOGGING_ENABLED
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#endif // mozilla_logging_h
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