/* -*- 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/. */
#ifndef mozilla_logging_h
#define mozilla_logging_h
#include <string.h>
#include <stdarg.h>
#include "mozilla/Assertions.h"
#include "mozilla/Atomics.h"
#include "mozilla/Attributes.h"
#include "mozilla/Likely.h"
// We normally have logging enabled everywhere, but measurements showed that
// having logging enabled on Android is quite expensive (hundreds of kilobytes
// for both the format strings for logging and the code to perform all the
// logging calls). Because retrieving logs from a mobile device is
// comparatively more difficult for Android than it is for desktop and because
// desktop machines tend to be less space/bandwidth-constrained than Android
// devices, we've chosen to leave logging enabled on desktop, but disabled on
// Android. Given that logging can still be useful for development purposes,
// however, we leave logging enabled on Android developer builds.
#if !defined(ANDROID) || !defined(RELEASE_OR_BETA)
#define MOZ_LOGGING_ENABLED 1
#else
#define MOZ_LOGGING_ENABLED 0
#endif
namespace mozilla {
// While not a 100% mapping to PR_LOG's numeric values, mozilla::LogLevel does
// maintain a direct mapping for the Disabled, Debug and Verbose levels.
//
// Mappings of LogLevel to PR_LOG's numeric values:
//
// +---------+------------------+-----------------+
// | Numeric | NSPR Logging | Mozilla Logging |
// +---------+------------------+-----------------+
// | 0 | PR_LOG_NONE | Disabled |
// | 1 | PR_LOG_ALWAYS | Error |
// | 2 | PR_LOG_ERROR | Warning |
// | 3 | PR_LOG_WARNING | Info |
// | 4 | PR_LOG_DEBUG | Debug |
// | 5 | PR_LOG_DEBUG + 1 | Verbose |
// +---------+------------------+-----------------+
//
enum class LogLevel {
Disabled = 0,
Error,
Warning,
Info,
Debug,
Verbose,
};
/**
* Safely converts an integer into a valid LogLevel.
*/
LogLevel ToLogLevel(int32_t aLevel);
class LogModule {
public:
~LogModule() { ::free(mName); }
/**
* Retrieves the module with the given name. If it does not already exist
* it will be created.
*
* @param aName The name of the module.
* @return A log module for the given name. This may be shared.
*/
static LogModule* Get(const char* aName);
static void Init();
/**
* Sets the log file to the given filename.
*/
static void SetLogFile(const char* aFilename);
/**
* @param aBuffer - pointer to a buffer
* @param aLength - the length of the buffer
*
* @return the actual length of the filepath.
*/
static uint32_t GetLogFile(char* aBuffer, size_t aLength);
/**
* @param aAddTimestamp If we should log a time stamp with every message.
*/
static void SetAddTimestamp(bool aAddTimestamp);
/**
* @param aIsSync If we should flush the file after every logged message.
*/
static void SetIsSync(bool aIsSync);
/**
* Indicates whether or not the given log level is enabled.
*/
bool ShouldLog(LogLevel aLevel) const { return mLevel >= aLevel; }
/**
* Retrieves the log module's current level.
*/
LogLevel Level() const { return mLevel; }
/**
* Sets the log module's level.
*/
void SetLevel(LogLevel level) { mLevel = level; }
/**
* Print a log message for this module.
*/
void Printv(LogLevel aLevel, const char* aFmt, va_list aArgs) const
MOZ_FORMAT_PRINTF(3, 0);
/**
* Retrieves the module name.
*/
const char* Name() const { return mName; }
private:
friend class LogModuleManager;
explicit LogModule(const char* aName, LogLevel aLevel)
: mName(strdup(aName)), mLevel(aLevel) {}
LogModule(LogModule&) = delete;
LogModule& operator=(const LogModule&) = delete;
char* mName;
Atomic<LogLevel, Relaxed> mLevel;
};
/**
* Helper class that lazy loads the given log module. This is safe to use for
* declaring static references to log modules and can be used as a replacement
* for accessing a LogModule directly.
*
* Example usage:
* static LazyLogModule sLayoutLog("layout");
*
* void Foo() {
* MOZ_LOG(sLayoutLog, LogLevel::Verbose, ("Entering foo"));
* }
*/
class LazyLogModule final {
public:
explicit constexpr LazyLogModule(const char* aLogName)
: mLogName(aLogName), mLog(nullptr) {}
operator LogModule*();
private:
const char* const mLogName;
Atomic<LogModule*, ReleaseAcquire> mLog;
};
namespace detail {
inline bool log_test(const LogModule* module, LogLevel level) {
MOZ_ASSERT(level != LogLevel::Disabled);
return module && module->ShouldLog(level);
}
void log_print(const LogModule* aModule, LogLevel aLevel, const char* aFmt, ...)
MOZ_FORMAT_PRINTF(3, 4);
} // namespace detail
} // namespace mozilla
// Helper macro used convert MOZ_LOG's third parameter, |_args|, from a
// parenthesized form to a varargs form. For example:
// ("%s", "a message") => "%s", "a message"
#define MOZ_LOG_EXPAND_ARGS(...) __VA_ARGS__
#if MOZ_LOGGING_ENABLED
#define MOZ_LOG_TEST(_module, _level) mozilla::detail::log_test(_module, _level)
#else
// Define away MOZ_LOG_TEST here so the compiler will fold away entire
// logging blocks via dead code elimination, e.g.:
//
// if (MOZ_LOG_TEST(...)) {
// ...compute things to log and log them...
// }
#define MOZ_LOG_TEST(_module, _level) false
#endif
// The natural definition of the MOZ_LOG macro would expand to:
//
// do {
// if (MOZ_LOG_TEST(_module, _level)) {
// mozilla::detail::log_print(_module, ...);
// }
// } while (0)
//
// However, since _module is a LazyLogModule, and we need to call
// LazyLogModule::operator() to get a LogModule* for the MOZ_LOG_TEST
// macro and for the logging call, we'll wind up doing *two* calls, one
// for each, rather than a single call. The compiler is not able to
// fold the two calls into one, and the extra call can have a
// significant effect on code size. (Making LazyLogModule::operator() a
// `const` function does not have any effect.)
//
// Therefore, we will have to make a single call ourselves. But again,
// the natural definition:
//
// do {
// ::mozilla::LogModule* real_module = _module;
// if (MOZ_LOG_TEST(real_module, _level)) {
// mozilla::detail::log_print(real_module, ...);
// }
// } while (0)
//
// also has a problem: if logging is disabled, then we will call
// LazyLogModule::operator() unnecessarily, and the compiler will not be
// able to optimize away the call as dead code. We would like to avoid
// such a scenario, as the whole point of disabling logging is for the
// logging statements to not generate any code.
//
// Therefore, we need different definitions of MOZ_LOG, depending on
// whether logging is enabled or not. (We need an actual definition of
// MOZ_LOG even when logging is disabled to ensure the compiler sees that
// variables only used during logging code are actually used, even if the
// code will never be executed.) Hence, the following code.
#if MOZ_LOGGING_ENABLED
#define MOZ_LOG(_module, _level, _args) \
do { \
const ::mozilla::LogModule* moz_real_module = _module; \
if (MOZ_LOG_TEST(moz_real_module, _level)) { \
mozilla::detail::log_print(moz_real_module, _level, \
MOZ_LOG_EXPAND_ARGS _args); \
} \
} while (0)
#else
#define MOZ_LOG(_module, _level, _args) \
do { \
if (MOZ_LOG_TEST(_module, _level)) { \
mozilla::detail::log_print(_module, _level, MOZ_LOG_EXPAND_ARGS _args); \
} \
} while (0)
#endif
// This #define is a Logging.h-only knob! Don't encourage people to get fancy
// with their log definitions by exporting it outside of Logging.h.
#undef MOZ_LOGGING_ENABLED
#endif // mozilla_logging_h