The Tor Browser / file revision

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.

 // Use of this source code is governed by a BSD-style license that can be

 // found in the LICENSE file.

 #ifndef BASE_LOGGING_H_

 #define BASE_LOGGING_H_

 #include <cassert>

 #include <string>

 #include <cstring>

 #include <sstream>

 #include "base/base_export.h"

 #include "base/basictypes.h"

 #include "base/debug/debugger.h"

 #include "build/build_config.h"

 //

 // Optional message capabilities

 // -----------------------------

 // Assertion failed messages and fatal errors are displayed in a dialog box

 // before the application exits. However, running this UI creates a message

 // loop, which causes application messages to be processed and potentially

 // dispatched to existing application windows. Since the application is in a

 // bad state when this assertion dialog is displayed, these messages may not

 // get processed and hang the dialog, or the application might go crazy.

 //

 // Therefore, it can be beneficial to display the error dialog in a separate

 // process from the main application. When the logging system needs to display

 // a fatal error dialog box, it will look for a program called

 // "DebugMessage.exe" in the same directory as the application executable. It

 // will run this application with the message as the command line, and will

 // not include the name of the application as is traditional for easier

 // parsing.

 //

 // The code for DebugMessage.exe is only one line. In WinMain, do:

 //   MessageBox(NULL, GetCommandLineW(), L"Fatal Error", 0);

 //

 // If DebugMessage.exe is not found, the logging code will use a normal

 // MessageBox, potentially causing the problems discussed above.

 // Instructions

 // ------------

 //

 // Make a bunch of macros for logging.  The way to log things is to stream

 // things to LOG(<a particular severity level>).  E.g.,

 //

 //   LOG(INFO) << "Found " << num_cookies << " cookies";

 //

 // You can also do conditional logging:

 //

 //   LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";

 //

 // The above will cause log messages to be output on the 1st, 11th, 21st, ...

 // times it is executed.  Note that the special COUNTER value is used to

 // identify which repetition is happening.

 //

 // The CHECK(condition) macro is active in both debug and release builds and

 // effectively performs a LOG(FATAL) which terminates the process and

 // generates a crashdump unless a debugger is attached.

 //

 // There are also "debug mode" logging macros like the ones above:

 //

 //   DLOG(INFO) << "Found cookies";

 //

 //   DLOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";

 //

 // All "debug mode" logging is compiled away to nothing for non-debug mode

 // compiles.  LOG_IF and development flags also work well together

 // because the code can be compiled away sometimes.

 //

 // We also have

 //

 //   LOG_ASSERT(assertion);

 //   DLOG_ASSERT(assertion);

 //

 // which is syntactic sugar for {,D}LOG_IF(FATAL, assert fails) << assertion;

 //

 // There are "verbose level" logging macros.  They look like

 //

 //   VLOG(1) << "I'm printed when you run the program with --v=1 or more";

 //   VLOG(2) << "I'm printed when you run the program with --v=2 or more";

 //

 // These always log at the INFO log level (when they log at all).

 // The verbose logging can also be turned on module-by-module.  For instance,

 //    --vmodule=profile=2,icon_loader=1,browser_*=3,*/chromeos/*=4 --v=0

 // will cause:

 //   a. VLOG(2) and lower messages to be printed from profile.{h,cc}

 //   b. VLOG(1) and lower messages to be printed from icon_loader.{h,cc}

 //   c. VLOG(3) and lower messages to be printed from files prefixed with

 //      "browser"

 //   d. VLOG(4) and lower messages to be printed from files under a

 //     "chromeos" directory.

 //   e. VLOG(0) and lower messages to be printed from elsewhere

 //

 // The wildcarding functionality shown by (c) supports both '*' (match

 // 0 or more characters) and '?' (match any single character)

 // wildcards.  Any pattern containing a forward or backward slash will

 // be tested against the whole pathname and not just the module.

 // E.g., "*/foo/bar/*=2" would change the logging level for all code

 // in source files under a "foo/bar" directory.

 //

 // There's also VLOG_IS_ON(n) "verbose level" condition macro. To be used as

 //

 //   if (VLOG_IS_ON(2)) {

 //     // do some logging preparation and logging

 //     // that can't be accomplished with just VLOG(2) << ...;

 //   }

 //

 // There is also a VLOG_IF "verbose level" condition macro for sample

 // cases, when some extra computation and preparation for logs is not

 // needed.

 //

 //   VLOG_IF(1, (size > 1024))

 //      << "I'm printed when size is more than 1024 and when you run the "

 //         "program with --v=1 or more";

 //

 // We also override the standard 'assert' to use 'DLOG_ASSERT'.

 //

 // Lastly, there is:

 //

 //   PLOG(ERROR) << "Couldn't do foo";

 //   DPLOG(ERROR) << "Couldn't do foo";

 //   PLOG_IF(ERROR, cond) << "Couldn't do foo";

 //   DPLOG_IF(ERROR, cond) << "Couldn't do foo";

 //   PCHECK(condition) << "Couldn't do foo";

 //   DPCHECK(condition) << "Couldn't do foo";

 //

 // which append the last system error to the message in string form (taken from

 // GetLastError() on Windows and errno on POSIX).

 //

 // The supported severity levels for macros that allow you to specify one

 // are (in increasing order of severity) INFO, WARNING, ERROR, ERROR_REPORT,

 // and FATAL.

 //

 // Very important: logging a message at the FATAL severity level causes

 // the program to terminate (after the message is logged).

 //

 // Note the special severity of ERROR_REPORT only available/relevant in normal

 // mode, which displays error dialog without terminating the program. There is

 // no error dialog for severity ERROR or below in normal mode.

 //

 // There is also the special severity of DFATAL, which logs FATAL in

 // debug mode, ERROR in normal mode.

 namespace logging {

 // TODO(avi): do we want to do a unification of character types here?

 #if defined(OS_WIN)

 typedef wchar_t PathChar;

 #else

 typedef char PathChar;

 #endif

 // Where to record logging output? A flat file and/or system debug log

 // via OutputDebugString.

 enum LoggingDestination {

   LOG_NONE                = 0,

   LOG_TO_FILE             = 1 << 0,

   LOG_TO_SYSTEM_DEBUG_LOG = 1 << 1,

   LOG_TO_ALL = LOG_TO_FILE | LOG_TO_SYSTEM_DEBUG_LOG,

   // On Windows, use a file next to the exe; on POSIX platforms, where

   // it may not even be possible to locate the executable on disk, use

   // stderr.

 #if defined(OS_WIN)

   LOG_DEFAULT = LOG_TO_FILE,

 #elif defined(OS_POSIX)

   LOG_DEFAULT = LOG_TO_SYSTEM_DEBUG_LOG,

 #endif

 };

 // Indicates that the log file should be locked when being written to.

 // Unless there is only one single-threaded process that is logging to

 // the log file, the file should be locked during writes to make each

 // log outut atomic. Other writers will block.

 //

 // All processes writing to the log file must have their locking set for it to

 // work properly. Defaults to LOCK_LOG_FILE.

 enum LogLockingState { LOCK_LOG_FILE, DONT_LOCK_LOG_FILE };

 // On startup, should we delete or append to an existing log file (if any)?

 // Defaults to APPEND_TO_OLD_LOG_FILE.

 enum OldFileDeletionState { DELETE_OLD_LOG_FILE, APPEND_TO_OLD_LOG_FILE };

 enum DcheckState {

   DISABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS,

   ENABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS

 };

 struct BASE_EXPORT LoggingSettings {

   // The defaults values are:

   //

   //  logging_dest: LOG_DEFAULT

   //  log_file:     NULL

   //  lock_log:     LOCK_LOG_FILE

   //  delete_old:   APPEND_TO_OLD_LOG_FILE

   //  dcheck_state: DISABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS

   LoggingSettings();

   LoggingDestination logging_dest;

   // The three settings below have an effect only when LOG_TO_FILE is

   // set in |logging_dest|.

   const PathChar* log_file;

   LogLockingState lock_log;

   OldFileDeletionState delete_old;

   DcheckState dcheck_state;

 };

 // Define different names for the BaseInitLoggingImpl() function depending on

 // whether NDEBUG is defined or not so that we'll fail to link if someone tries

 // to compile logging.cc with NDEBUG but includes logging.h without defining it,

 // or vice versa.

 #if NDEBUG

 #define BaseInitLoggingImpl BaseInitLoggingImpl_built_with_NDEBUG

 #else

 #define BaseInitLoggingImpl BaseInitLoggingImpl_built_without_NDEBUG

 #endif

 // Implementation of the InitLogging() method declared below.  We use a

 // more-specific name so we can #define it above without affecting other code

 // that has named stuff "InitLogging".

 BASE_EXPORT bool BaseInitLoggingImpl(const LoggingSettings& settings);

 // Sets the log file name and other global logging state. Calling this function

 // is recommended, and is normally done at the beginning of application init.

 // If you don't call it, all the flags will be initialized to their default

 // values, and there is a race condition that may leak a critical section

 // object if two threads try to do the first log at the same time.

 // See the definition of the enums above for descriptions and default values.

 //

 // The default log file is initialized to "debug.log" in the application

 // directory. You probably don't want this, especially since the program

 // directory may not be writable on an enduser's system.

 //

 // This function may be called a second time to re-direct logging (e.g after

 // loging in to a user partition), however it should never be called more than

 // twice.

 inline bool InitLogging(const LoggingSettings& settings) {

   return BaseInitLoggingImpl(settings);

 }

 // Sets the log level. Anything at or above this level will be written to the

 // log file/displayed to the user (if applicable). Anything below this level

 // will be silently ignored. The log level defaults to 0 (everything is logged

 // up to level INFO) if this function is not called.

 // Note that log messages for VLOG(x) are logged at level -x, so setting

 // the min log level to negative values enables verbose logging.

 BASE_EXPORT void SetMinLogLevel(int level);

 // Gets the current log level.

 BASE_EXPORT int GetMinLogLevel();

 // Gets the VLOG default verbosity level.

 BASE_EXPORT int GetVlogVerbosity();

 // Gets the current vlog level for the given file (usually taken from

 // __FILE__).

 // Note that |N| is the size *with* the null terminator.

 BASE_EXPORT int GetVlogLevelHelper(const char* file_start, size_t N);

 template <size_t N>

 int GetVlogLevel(const char (&file)[N]) {

   return GetVlogLevelHelper(file, N);

 }

 // Sets the common items you want to be prepended to each log message.

 // process and thread IDs default to off, the timestamp defaults to on.

 // If this function is not called, logging defaults to writing the timestamp

 // only.

 BASE_EXPORT void SetLogItems(bool enable_process_id, bool enable_thread_id,

                              bool enable_timestamp, bool enable_tickcount);

 // Sets whether or not you'd like to see fatal debug messages popped up in

 // a dialog box or not.

 // Dialogs are not shown by default.

 BASE_EXPORT void SetShowErrorDialogs(bool enable_dialogs);

 // Sets the Log Assert Handler that will be used to notify of check failures.

 // The default handler shows a dialog box and then terminate the process,

 // however clients can use this function to override with their own handling

 // (e.g. a silent one for Unit Tests)

 typedef void (*LogAssertHandlerFunction)(const std::string& str);

 BASE_EXPORT void SetLogAssertHandler(LogAssertHandlerFunction handler);

 // Sets the Log Report Handler that will be used to notify of check failures

 // in non-debug mode. The default handler shows a dialog box and continues

 // the execution, however clients can use this function to override with their

 // own handling.

 typedef void (*LogReportHandlerFunction)(const std::string& str);

 BASE_EXPORT void SetLogReportHandler(LogReportHandlerFunction handler);

 // Sets the Log Message Handler that gets passed every log message before

 // it's sent to other log destinations (if any).

 // Returns true to signal that it handled the message and the message

 // should not be sent to other log destinations.

 typedef bool (*LogMessageHandlerFunction)(int severity,

     const char* file, int line, size_t message_start, const std::string& str);

 BASE_EXPORT void SetLogMessageHandler(LogMessageHandlerFunction handler);

 BASE_EXPORT LogMessageHandlerFunction GetLogMessageHandler();

 typedef int LogSeverity;

 const LogSeverity LOG_VERBOSE = -1;  // This is level 1 verbosity

 // Note: the log severities are used to index into the array of names,

 // see log_severity_names.

 const LogSeverity LOG_INFO = 0;

 const LogSeverity LOG_WARNING = 1;

 const LogSeverity LOG_ERROR = 2;

 const LogSeverity LOG_ERROR_REPORT = 3;

 const LogSeverity LOG_FATAL = 4;

 const LogSeverity LOG_NUM_SEVERITIES = 5;

 // LOG_DFATAL is LOG_FATAL in debug mode, ERROR in normal mode

 #ifdef NDEBUG

 const LogSeverity LOG_DFATAL = LOG_ERROR;

 #else

 const LogSeverity LOG_DFATAL = LOG_FATAL;

 #endif

 // A few definitions of macros that don't generate much code. These are used

 // by LOG() and LOG_IF, etc. Since these are used all over our code, it's

 // better to have compact code for these operations.

 #define COMPACT_GOOGLE_LOG_EX_INFO(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, logging::LOG_INFO , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_EX_WARNING(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, logging::LOG_WARNING , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_EX_ERROR(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, logging::LOG_ERROR , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_EX_ERROR_REPORT(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, \

                      logging::LOG_ERROR_REPORT , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_EX_FATAL(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, logging::LOG_FATAL , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_EX_DFATAL(ClassName, ...) \

   logging::ClassName(__FILE__, __LINE__, logging::LOG_DFATAL , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_INFO \

   COMPACT_GOOGLE_LOG_EX_INFO(LogMessage)

 #define COMPACT_GOOGLE_LOG_WARNING \

   COMPACT_GOOGLE_LOG_EX_WARNING(LogMessage)

 #define COMPACT_GOOGLE_LOG_ERROR \

   COMPACT_GOOGLE_LOG_EX_ERROR(LogMessage)

 #define COMPACT_GOOGLE_LOG_ERROR_REPORT \

   COMPACT_GOOGLE_LOG_EX_ERROR_REPORT(LogMessage)

 #define COMPACT_GOOGLE_LOG_FATAL \

   COMPACT_GOOGLE_LOG_EX_FATAL(LogMessage)

 #define COMPACT_GOOGLE_LOG_DFATAL \

   COMPACT_GOOGLE_LOG_EX_DFATAL(LogMessage)

 #if defined(OS_WIN)

 // wingdi.h defines ERROR to be 0. When we call LOG(ERROR), it gets

 // substituted with 0, and it expands to COMPACT_GOOGLE_LOG_0. To allow us

 // to keep using this syntax, we define this macro to do the same thing

 // as COMPACT_GOOGLE_LOG_ERROR, and also define ERROR the same way that

 // the Windows SDK does for consistency.

 #define ERROR 0

 #define COMPACT_GOOGLE_LOG_EX_0(ClassName, ...) \

   COMPACT_GOOGLE_LOG_EX_ERROR(ClassName , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_0 COMPACT_GOOGLE_LOG_ERROR

 // Needed for LOG_IS_ON(ERROR).

 const LogSeverity LOG_0 = LOG_ERROR;

 #endif

 // As special cases, we can assume that LOG_IS_ON(ERROR_REPORT) and

 // LOG_IS_ON(FATAL) always hold.  Also, LOG_IS_ON(DFATAL) always holds

 // in debug mode.  In particular, CHECK()s will always fire if they

 // fail.

 #define LOG_IS_ON(severity) \

   ((::logging::LOG_ ## severity) >= ::logging::GetMinLogLevel())

 // We can't do any caching tricks with VLOG_IS_ON() like the

 // google-glog version since it requires GCC extensions.  This means

 // that using the v-logging functions in conjunction with --vmodule

 // may be slow.

 #define VLOG_IS_ON(verboselevel) \

   ((verboselevel) <= ::logging::GetVlogLevel(__FILE__))

 // Helper macro which avoids evaluating the arguments to a stream if

 // the condition doesn't hold.

 #define LAZY_STREAM(stream, condition)                                  \

   !(condition) ? (void) 0 : ::logging::LogMessageVoidify() & (stream)

 // We use the preprocessor's merging operator, "##", so that, e.g.,

 // LOG(INFO) becomes the token COMPACT_GOOGLE_LOG_INFO.  There's some funny

 // subtle difference between ostream member streaming functions (e.g.,

 // ostream::operator<<(int) and ostream non-member streaming functions

 // (e.g., ::operator<<(ostream&, string&): it turns out that it's

 // impossible to stream something like a string directly to an unnamed

 // ostream. We employ a neat hack by calling the stream() member

 // function of LogMessage which seems to avoid the problem.

 #define LOG_STREAM(severity) COMPACT_GOOGLE_LOG_ ## severity.stream()

 #define LOG(severity) LAZY_STREAM(LOG_STREAM(severity), LOG_IS_ON(severity))

 #define LOG_IF(severity, condition) \

   LAZY_STREAM(LOG_STREAM(severity), LOG_IS_ON(severity) && (condition))

 #define SYSLOG(severity) LOG(severity)

 #define SYSLOG_IF(severity, condition) LOG_IF(severity, condition)

 // The VLOG macros log with negative verbosities.

 #define VLOG_STREAM(verbose_level) \

   logging::LogMessage(__FILE__, __LINE__, -verbose_level).stream()

 #define VLOG(verbose_level) \

   LAZY_STREAM(VLOG_STREAM(verbose_level), VLOG_IS_ON(verbose_level))

 #define VLOG_IF(verbose_level, condition) \

   LAZY_STREAM(VLOG_STREAM(verbose_level), \

       VLOG_IS_ON(verbose_level) && (condition))

 #if defined (OS_WIN)

 #define VPLOG_STREAM(verbose_level) \

   logging::Win32ErrorLogMessage(__FILE__, __LINE__, -verbose_level, \

     ::logging::GetLastSystemErrorCode()).stream()

 #elif defined(OS_POSIX)

 #define VPLOG_STREAM(verbose_level) \

   logging::ErrnoLogMessage(__FILE__, __LINE__, -verbose_level, \

     ::logging::GetLastSystemErrorCode()).stream()

 #endif

 #define VPLOG(verbose_level) \

   LAZY_STREAM(VPLOG_STREAM(verbose_level), VLOG_IS_ON(verbose_level))

 #define VPLOG_IF(verbose_level, condition) \

   LAZY_STREAM(VPLOG_STREAM(verbose_level), \

     VLOG_IS_ON(verbose_level) && (condition))

 // TODO(akalin): Add more VLOG variants, e.g. VPLOG.

 #define LOG_ASSERT(condition)  \

   LOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "

 #define SYSLOG_ASSERT(condition) \

   SYSLOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "

 #if defined(OS_WIN)

 #define LOG_GETLASTERROR_STREAM(severity) \

   COMPACT_GOOGLE_LOG_EX_ ## severity(Win32ErrorLogMessage, \

       ::logging::GetLastSystemErrorCode()).stream()

 #define LOG_GETLASTERROR(severity) \

   LAZY_STREAM(LOG_GETLASTERROR_STREAM(severity), LOG_IS_ON(severity))

 #define LOG_GETLASTERROR_MODULE_STREAM(severity, module) \

   COMPACT_GOOGLE_LOG_EX_ ## severity(Win32ErrorLogMessage, \

       ::logging::GetLastSystemErrorCode(), module).stream()

 #define LOG_GETLASTERROR_MODULE(severity, module)                       \

   LAZY_STREAM(LOG_GETLASTERROR_STREAM(severity, module),                \

               LOG_IS_ON(severity))

 // PLOG_STREAM is used by PLOG, which is the usual error logging macro

 // for each platform.

 #define PLOG_STREAM(severity) LOG_GETLASTERROR_STREAM(severity)

 #elif defined(OS_POSIX)

 #define LOG_ERRNO_STREAM(severity) \

   COMPACT_GOOGLE_LOG_EX_ ## severity(ErrnoLogMessage, \

       ::logging::GetLastSystemErrorCode()).stream()

 #define LOG_ERRNO(severity) \

   LAZY_STREAM(LOG_ERRNO_STREAM(severity), LOG_IS_ON(severity))

 // PLOG_STREAM is used by PLOG, which is the usual error logging macro

 // for each platform.

 #define PLOG_STREAM(severity) LOG_ERRNO_STREAM(severity)

 #endif

 #define PLOG(severity)                                          \

   LAZY_STREAM(PLOG_STREAM(severity), LOG_IS_ON(severity))

 #define PLOG_IF(severity, condition) \

   LAZY_STREAM(PLOG_STREAM(severity), LOG_IS_ON(severity) && (condition))

 #if !defined(NDEBUG)

 // Debug builds always include DCHECK and DLOG.

 #undef LOGGING_IS_OFFICIAL_BUILD

 #define LOGGING_IS_OFFICIAL_BUILD 0

 #elif defined(OFFICIAL_BUILD)

 // Official release builds always disable and remove DCHECK and DLOG.

 #undef LOGGING_IS_OFFICIAL_BUILD

 #define LOGGING_IS_OFFICIAL_BUILD 1

 #elif !defined(LOGGING_IS_OFFICIAL_BUILD)

 // Unless otherwise specified, unofficial release builds include

 // DCHECK and DLOG.

 #define LOGGING_IS_OFFICIAL_BUILD 0

 #endif

 // The actual stream used isn't important.

 #define EAT_STREAM_PARAMETERS                                           \

   true ? (void) 0 : ::logging::LogMessageVoidify() & LOG_STREAM(FATAL)

 // CHECK dies with a fatal error if condition is not true.  It is *not*

 // controlled by NDEBUG, so the check will be executed regardless of

 // compilation mode.

 //

 // We make sure CHECK et al. always evaluates their arguments, as

 // doing CHECK(FunctionWithSideEffect()) is a common idiom.

 #if LOGGING_IS_OFFICIAL_BUILD

 // Make all CHECK functions discard their log strings to reduce code

 // bloat for official builds.

 // TODO(akalin): This would be more valuable if there were some way to

 // remove BreakDebugger() from the backtrace, perhaps by turning it

 // into a macro (like __debugbreak() on Windows).

 #define CHECK(condition)                                                \

   !(condition) ? ::base::debug::BreakDebugger() : EAT_STREAM_PARAMETERS

 #define PCHECK(condition) CHECK(condition)

 #define CHECK_OP(name, op, val1, val2) CHECK((val1) op (val2))

 #else

 #define CHECK(condition)                       \

   LAZY_STREAM(LOG_STREAM(FATAL), !(condition)) \

   << "Check failed: " #condition ". "

 #define PCHECK(condition) \

   LAZY_STREAM(PLOG_STREAM(FATAL), !(condition)) \

   << "Check failed: " #condition ". "

 // Helper macro for binary operators.

 // Don't use this macro directly in your code, use CHECK_EQ et al below.

 //

 // TODO(akalin): Rewrite this so that constructs like if (...)

 // CHECK_EQ(...) else { ... } work properly.

 #define CHECK_OP(name, op, val1, val2)                          \

   if (std::string* _result =                                    \

       logging::Check##name##Impl((val1), (val2),                \

                                  #val1 " " #op " " #val2))      \

     logging::LogMessage(__FILE__, __LINE__, _result).stream()

 #endif

 // Build the error message string.  This is separate from the "Impl"

 // function template because it is not performance critical and so can

 // be out of line, while the "Impl" code should be inline.  Caller

 // takes ownership of the returned string.

 template<class t1, class t2>

 std::string* MakeCheckOpString(const t1& v1, const t2& v2, const char* names) {

   std::ostringstream ss;

   ss << names << " (" << v1 << " vs. " << v2 << ")";

   std::string* msg = new std::string(ss.str());

   return msg;

 }

 // MSVC doesn't like complex extern templates and DLLs.

 #if !defined(COMPILER_MSVC)

 // Commonly used instantiations of MakeCheckOpString<>. Explicitly instantiated

 // in logging.cc.

 extern template BASE_EXPORT std::string* MakeCheckOpString<int, int>(

     const int&, const int&, const char* names);

 extern template BASE_EXPORT

 std::string* MakeCheckOpString<unsigned long, unsigned long>(

     const unsigned long&, const unsigned long&, const char* names);

 extern template BASE_EXPORT

 std::string* MakeCheckOpString<unsigned long, unsigned int>(

     const unsigned long&, const unsigned int&, const char* names);

 extern template BASE_EXPORT

 std::string* MakeCheckOpString<unsigned int, unsigned long>(

     const unsigned int&, const unsigned long&, const char* names);

 extern template BASE_EXPORT

 std::string* MakeCheckOpString<std::string, std::string>(

     const std::string&, const std::string&, const char* name);

 #endif

 // Helper functions for CHECK_OP macro.

 // The (int, int) specialization works around the issue that the compiler

 // will not instantiate the template version of the function on values of

 // unnamed enum type - see comment below.

 #define DEFINE_CHECK_OP_IMPL(name, op) \

   template <class t1, class t2> \

   inline std::string* Check##name##Impl(const t1& v1, const t2& v2, \

                                         const char* names) { \

     if (v1 op v2) return NULL; \

     else return MakeCheckOpString(v1, v2, names); \

   } \

   inline std::string* Check##name##Impl(int v1, int v2, const char* names) { \

     if (v1 op v2) return NULL; \

     else return MakeCheckOpString(v1, v2, names); \

   }

 DEFINE_CHECK_OP_IMPL(EQ, ==)

 DEFINE_CHECK_OP_IMPL(NE, !=)

 DEFINE_CHECK_OP_IMPL(LE, <=)

 DEFINE_CHECK_OP_IMPL(LT, < )

 DEFINE_CHECK_OP_IMPL(GE, >=)

 DEFINE_CHECK_OP_IMPL(GT, > )

 #undef DEFINE_CHECK_OP_IMPL

 #define CHECK_EQ(val1, val2) CHECK_OP(EQ, ==, val1, val2)

 #define CHECK_NE(val1, val2) CHECK_OP(NE, !=, val1, val2)

 #define CHECK_LE(val1, val2) CHECK_OP(LE, <=, val1, val2)

 #define CHECK_LT(val1, val2) CHECK_OP(LT, < , val1, val2)

 #define CHECK_GE(val1, val2) CHECK_OP(GE, >=, val1, val2)

 #define CHECK_GT(val1, val2) CHECK_OP(GT, > , val1, val2)

 #if LOGGING_IS_OFFICIAL_BUILD

 // In order to have optimized code for official builds, remove DLOGs and

 // DCHECKs.

 #define ENABLE_DLOG 0

 #define ENABLE_DCHECK 0

 #elif defined(NDEBUG)

 // Otherwise, if we're a release build, remove DLOGs but not DCHECKs

 // (since those can still be turned on via a command-line flag).

 #define ENABLE_DLOG 0

 #define ENABLE_DCHECK 1

 #else

 // Otherwise, we're a debug build so enable DLOGs and DCHECKs.

 #define ENABLE_DLOG 1

 #define ENABLE_DCHECK 1

 #endif

 // Definitions for DLOG et al.

 #if ENABLE_DLOG

 #define DLOG_IS_ON(severity) LOG_IS_ON(severity)

 #define DLOG_IF(severity, condition) LOG_IF(severity, condition)

 #define DLOG_ASSERT(condition) LOG_ASSERT(condition)

 #define DPLOG_IF(severity, condition) PLOG_IF(severity, condition)

 #define DVLOG_IF(verboselevel, condition) VLOG_IF(verboselevel, condition)

 #define DVPLOG_IF(verboselevel, condition) VPLOG_IF(verboselevel, condition)

 #else  // ENABLE_DLOG

 // If ENABLE_DLOG is off, we want to avoid emitting any references to

 // |condition| (which may reference a variable defined only if NDEBUG

 // is not defined).  Contrast this with DCHECK et al., which has

 // different behavior.

 #define DLOG_IS_ON(severity) false

 #define DLOG_IF(severity, condition) EAT_STREAM_PARAMETERS

 #define DLOG_ASSERT(condition) EAT_STREAM_PARAMETERS

 #define DPLOG_IF(severity, condition) EAT_STREAM_PARAMETERS

 #define DVLOG_IF(verboselevel, condition) EAT_STREAM_PARAMETERS

 #define DVPLOG_IF(verboselevel, condition) EAT_STREAM_PARAMETERS

 #endif  // ENABLE_DLOG

 // DEBUG_MODE is for uses like

 //   if (DEBUG_MODE) foo.CheckThatFoo();

 // instead of

 //   #ifndef NDEBUG

 //     foo.CheckThatFoo();

 //   #endif

 //

 // We tie its state to ENABLE_DLOG.

 enum { DEBUG_MODE = ENABLE_DLOG };

 #undef ENABLE_DLOG

 #define DLOG(severity)                                          \

   LAZY_STREAM(LOG_STREAM(severity), DLOG_IS_ON(severity))

 #if defined(OS_WIN)

 #define DLOG_GETLASTERROR(severity) \

   LAZY_STREAM(LOG_GETLASTERROR_STREAM(severity), DLOG_IS_ON(severity))

 #define DLOG_GETLASTERROR_MODULE(severity, module)                      \

   LAZY_STREAM(LOG_GETLASTERROR_STREAM(severity, module),                \

               DLOG_IS_ON(severity))

 #elif defined(OS_POSIX)

 #define DLOG_ERRNO(severity)                                    \

   LAZY_STREAM(LOG_ERRNO_STREAM(severity), DLOG_IS_ON(severity))

 #endif

 #define DPLOG(severity)                                         \

   LAZY_STREAM(PLOG_STREAM(severity), DLOG_IS_ON(severity))

 #define DVLOG(verboselevel) DVLOG_IF(verboselevel, VLOG_IS_ON(verboselevel))

 #define DVPLOG(verboselevel) DVPLOG_IF(verboselevel, VLOG_IS_ON(verboselevel))

 // Definitions for DCHECK et al.

 #if ENABLE_DCHECK

 #if defined(NDEBUG)

 BASE_EXPORT DcheckState get_dcheck_state();

 BASE_EXPORT void set_dcheck_state(DcheckState state);

 #if defined(DCHECK_ALWAYS_ON)

 #define DCHECK_IS_ON() true

 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \

   COMPACT_GOOGLE_LOG_EX_FATAL(ClassName , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_FATAL

 const LogSeverity LOG_DCHECK = LOG_FATAL;

 #else

 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \

   COMPACT_GOOGLE_LOG_EX_ERROR_REPORT(ClassName , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_ERROR_REPORT

 const LogSeverity LOG_DCHECK = LOG_ERROR_REPORT;

 #define DCHECK_IS_ON()                                                  \

   ((::logging::get_dcheck_state() ==                                        \

     ::logging::ENABLE_DCHECK_FOR_NON_OFFICIAL_RELEASE_BUILDS) &&        \

    LOG_IS_ON(DCHECK))

 #endif  // defined(DCHECK_ALWAYS_ON)

 #else  // defined(NDEBUG)

 // On a regular debug build, we want to have DCHECKs enabled.

 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \

   COMPACT_GOOGLE_LOG_EX_FATAL(ClassName , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_FATAL

 const LogSeverity LOG_DCHECK = LOG_FATAL;

 #define DCHECK_IS_ON() true

 #endif  // defined(NDEBUG)

 #else  // ENABLE_DCHECK

 // These are just dummy values since DCHECK_IS_ON() is always false in

 // this case.

 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \

   COMPACT_GOOGLE_LOG_EX_INFO(ClassName , ##__VA_ARGS__)

 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_INFO

 const LogSeverity LOG_DCHECK = LOG_INFO;

 #define DCHECK_IS_ON() false

 #endif  // ENABLE_DCHECK

 #undef ENABLE_DCHECK

 // DCHECK et al. make sure to reference |condition| regardless of

 // whether DCHECKs are enabled; this is so that we don't get unused

 // variable warnings if the only use of a variable is in a DCHECK.

 // This behavior is different from DLOG_IF et al.

 #define DCHECK(condition)                                           \

   LAZY_STREAM(LOG_STREAM(DCHECK), DCHECK_IS_ON() && !(condition))   \

   << "Check failed: " #condition ". "

 #define DPCHECK(condition)                                          \

   LAZY_STREAM(PLOG_STREAM(DCHECK), DCHECK_IS_ON() && !(condition))  \

   << "Check failed: " #condition ". "

 // Helper macro for binary operators.

 // Don't use this macro directly in your code, use DCHECK_EQ et al below.

 #define DCHECK_OP(name, op, val1, val2)                         \

   if (DCHECK_IS_ON())                                           \

     if (std::string* _result =                                  \

         logging::Check##name##Impl((val1), (val2),              \

                                    #val1 " " #op " " #val2))    \

       logging::LogMessage(                                      \

           __FILE__, __LINE__, ::logging::LOG_DCHECK,            \

           _result).stream()

 // Equality/Inequality checks - compare two values, and log a

 // LOG_DCHECK message including the two values when the result is not

 // as expected.  The values must have operator<<(ostream, ...)

 // defined.

 //

 // You may append to the error message like so:

 //   DCHECK_NE(1, 2) << ": The world must be ending!";

 //

 // We are very careful to ensure that each argument is evaluated exactly

 // once, and that anything which is legal to pass as a function argument is

 // legal here.  In particular, the arguments may be temporary expressions

 // which will end up being destroyed at the end of the apparent statement,

 // for example:

 //   DCHECK_EQ(string("abc")[1], 'b');

 //

 // WARNING: These may not compile correctly if one of the arguments is a pointer

 // and the other is NULL. To work around this, simply static_cast NULL to the

 // type of the desired pointer.

 #define DCHECK_EQ(val1, val2) DCHECK_OP(EQ, ==, val1, val2)

 #define DCHECK_NE(val1, val2) DCHECK_OP(NE, !=, val1, val2)

 #define DCHECK_LE(val1, val2) DCHECK_OP(LE, <=, val1, val2)

 #define DCHECK_LT(val1, val2) DCHECK_OP(LT, < , val1, val2)

 #define DCHECK_GE(val1, val2) DCHECK_OP(GE, >=, val1, val2)

 #define DCHECK_GT(val1, val2) DCHECK_OP(GT, > , val1, val2)

 #define NOTREACHED() DCHECK(false)

 // Redefine the standard assert to use our nice log files

 #undef assert

 #define assert(x) DLOG_ASSERT(x)

 // This class more or less represents a particular log message.  You

 // create an instance of LogMessage and then stream stuff to it.

 // When you finish streaming to it, ~LogMessage is called and the

 // full message gets streamed to the appropriate destination.

 //

 // You shouldn't actually use LogMessage's constructor to log things,

 // though.  You should use the LOG() macro (and variants thereof)

 // above.

 class BASE_EXPORT LogMessage {

  public:

   LogMessage(const char* file, int line, LogSeverity severity, int ctr);

   // Two special constructors that generate reduced amounts of code at

   // LOG call sites for common cases.

   //

   // Used for LOG(INFO): Implied are:

   // severity = LOG_INFO, ctr = 0

   //

   // Using this constructor instead of the more complex constructor above

   // saves a couple of bytes per call site.

   LogMessage(const char* file, int line);

   // Used for LOG(severity) where severity != INFO.  Implied

   // are: ctr = 0

   //

   // Using this constructor instead of the more complex constructor above

   // saves a couple of bytes per call site.

   LogMessage(const char* file, int line, LogSeverity severity);

   // A special constructor used for check failures.  Takes ownership

   // of the given string.

   // Implied severity = LOG_FATAL

   LogMessage(const char* file, int line, std::string* result);

   // A special constructor used for check failures, with the option to

   // specify severity.  Takes ownership of the given string.

   LogMessage(const char* file, int line, LogSeverity severity,

              std::string* result);

   ~LogMessage();

   std::ostream& stream() { return stream_; }

  private:

   void Init(const char* file, int line);

   LogSeverity severity_;

   std::ostringstream stream_;

   size_t message_start_;  // Offset of the start of the message (past prefix

                           // info).

   // The file and line information passed in to the constructor.

   const char* file_;

   const int line_;

 #if defined(OS_WIN)

   // Stores the current value of GetLastError in the constructor and restores

   // it in the destructor by calling SetLastError.

   // This is useful since the LogMessage class uses a lot of Win32 calls

   // that will lose the value of GLE and the code that called the log function

   // will have lost the thread error value when the log call returns.

   class SaveLastError {

    public:

     SaveLastError();

     ~SaveLastError();

     unsigned long get_error() const { return last_error_; }

    protected:

     unsigned long last_error_;

   };

   SaveLastError last_error_;

 #endif

   DISALLOW_COPY_AND_ASSIGN(LogMessage);

 };

 // A non-macro interface to the log facility; (useful

 // when the logging level is not a compile-time constant).

 inline void LogAtLevel(int const log_level, std::string const &msg) {

   LogMessage(__FILE__, __LINE__, log_level).stream() << msg;

 }

 // This class is used to explicitly ignore values in the conditional

 // logging macros.  This avoids compiler warnings like "value computed

 // is not used" and "statement has no effect".

 class LogMessageVoidify {

  public:

   LogMessageVoidify() { }

   // This has to be an operator with a precedence lower than << but

   // higher than ?:

   void operator&(std::ostream&) { }

 };

 #if defined(OS_WIN)

 typedef unsigned long SystemErrorCode;

 #elif defined(OS_POSIX)

 typedef int SystemErrorCode;

 #endif

 // Alias for ::GetLastError() on Windows and errno on POSIX. Avoids having to

 // pull in windows.h just for GetLastError() and DWORD.

 BASE_EXPORT SystemErrorCode GetLastSystemErrorCode();

 #if defined(OS_WIN)

 // Appends a formatted system message of the GetLastError() type.

 class BASE_EXPORT Win32ErrorLogMessage {

  public:

   Win32ErrorLogMessage(const char* file,

                        int line,

                        LogSeverity severity,

                        SystemErrorCode err,

                        const char* module);

   Win32ErrorLogMessage(const char* file,

                        int line,

                        LogSeverity severity,

                        SystemErrorCode err);

   // Appends the error message before destructing the encapsulated class.

   ~Win32ErrorLogMessage();

   std::ostream& stream() { return log_message_.stream(); }

  private:

   SystemErrorCode err_;

   // Optional name of the module defining the error.

   const char* module_;

   LogMessage log_message_;

   DISALLOW_COPY_AND_ASSIGN(Win32ErrorLogMessage);

 };

 #elif defined(OS_POSIX)

 // Appends a formatted system message of the errno type

 class BASE_EXPORT ErrnoLogMessage {

  public:

   ErrnoLogMessage(const char* file,

                   int line,

                   LogSeverity severity,

                   SystemErrorCode err);

   // Appends the error message before destructing the encapsulated class.

   ~ErrnoLogMessage();

   std::ostream& stream() { return log_message_.stream(); }

  private:

   SystemErrorCode err_;

   LogMessage log_message_;

   DISALLOW_COPY_AND_ASSIGN(ErrnoLogMessage);

 };

 #endif  // OS_WIN

 // Closes the log file explicitly if open.

 // NOTE: Since the log file is opened as necessary by the action of logging

 //       statements, there's no guarantee that it will stay closed

 //       after this call.

 BASE_EXPORT void CloseLogFile();

 // Async signal safe logging mechanism.

 BASE_EXPORT void RawLog(int level, const char* message);

 #define RAW_LOG(level, message) logging::RawLog(logging::LOG_ ## level, message)

 #define RAW_CHECK(condition)                                                   \

   do {                                                                         \

     if (!(condition))                                                          \

       logging::RawLog(logging::LOG_FATAL, "Check failed: " #condition "\n");   \

   } while (0)

 #if defined(OS_WIN)

 // Returns the default log file path.

 BASE_EXPORT std::wstring GetLogFileFullPath();

 #endif

 }  // namespace logging

 // These functions are provided as a convenience for logging, which is where we

 // use streams (it is against Google style to use streams in other places). It

 // is designed to allow you to emit non-ASCII Unicode strings to the log file,

 // which is normally ASCII. It is relatively slow, so try not to use it for

 // common cases. Non-ASCII characters will be converted to UTF-8 by these

 // operators.

 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const wchar_t* wstr);

 inline std::ostream& operator<<(std::ostream& out, const std::wstring& wstr) {

   return out << wstr.c_str();

 }

 // The NOTIMPLEMENTED() macro annotates codepaths which have

 // not been implemented yet.

 //

 // The implementation of this macro is controlled by NOTIMPLEMENTED_POLICY:

 //   0 -- Do nothing (stripped by compiler)

 //   1 -- Warn at compile time

 //   2 -- Fail at compile time

 //   3 -- Fail at runtime (DCHECK)

 //   4 -- [default] LOG(ERROR) at runtime

 //   5 -- LOG(ERROR) at runtime, only once per call-site

 #ifndef NOTIMPLEMENTED_POLICY

 #if defined(OS_ANDROID) && defined(OFFICIAL_BUILD)

 #define NOTIMPLEMENTED_POLICY 0

 #else

 // Select default policy: LOG(ERROR)

 #define NOTIMPLEMENTED_POLICY 4

 #endif

 #endif

 #if defined(COMPILER_GCC)

 // On Linux, with GCC, we can use __PRETTY_FUNCTION__ to get the demangled name

 // of the current function in the NOTIMPLEMENTED message.

 #define NOTIMPLEMENTED_MSG "Not implemented reached in " << __PRETTY_FUNCTION__

 #else

 #define NOTIMPLEMENTED_MSG "NOT IMPLEMENTED"

 #endif

 #if NOTIMPLEMENTED_POLICY == 0

 #define NOTIMPLEMENTED() EAT_STREAM_PARAMETERS

 #elif NOTIMPLEMENTED_POLICY == 1

 // TODO, figure out how to generate a warning

 #define NOTIMPLEMENTED() COMPILE_ASSERT(false, NOT_IMPLEMENTED)

 #elif NOTIMPLEMENTED_POLICY == 2

 #define NOTIMPLEMENTED() COMPILE_ASSERT(false, NOT_IMPLEMENTED)

 #elif NOTIMPLEMENTED_POLICY == 3

 #define NOTIMPLEMENTED() NOTREACHED()

 #elif NOTIMPLEMENTED_POLICY == 4

 #define NOTIMPLEMENTED() LOG(ERROR) << NOTIMPLEMENTED_MSG

 #elif NOTIMPLEMENTED_POLICY == 5

 #define NOTIMPLEMENTED() do {\

   static bool logged_once = false;\

   LOG_IF(ERROR, !logged_once) << NOTIMPLEMENTED_MSG;\

   logged_once = true;\

 } while(0);\

 EAT_STREAM_PARAMETERS

 #endif

 #endif  // BASE_LOGGING_H_