base/logging.h

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_LOGGING_H_
   6 #define BASE_LOGGING_H_
   7
   8 #include <cassert>
   9 #include <string>
  10 #include <cstring>
  11 #include <sstream>
  12
  13 #include "base/base_export.h"
  14 #include "base/basictypes.h"
  15 #include "base/debug/debugger.h"
  16 #include "build/build_config.h"
  17
  18 //
  19 // Optional message capabilities
  20 // -----------------------------
  21 // Assertion failed messages and fatal errors are displayed in a dialog box
  22 // before the application exits. However, running this UI creates a message
  23 // loop, which causes application messages to be processed and potentially
  24 // dispatched to existing application windows. Since the application is in a
  25 // bad state when this assertion dialog is displayed, these messages may not
  26 // get processed and hang the dialog, or the application might go crazy.
  27 //
  28 // Therefore, it can be beneficial to display the error dialog in a separate
  29 // process from the main application. When the logging system needs to display
  30 // a fatal error dialog box, it will look for a program called
  31 // "DebugMessage.exe" in the same directory as the application executable. It
  32 // will run this application with the message as the command line, and will
  33 // not include the name of the application as is traditional for easier
  34 // parsing.
  35 //
  36 // The code for DebugMessage.exe is only one line. In WinMain, do:
  37 //   MessageBox(NULL, GetCommandLineW(), L"Fatal Error", 0);
  38 //
  39 // If DebugMessage.exe is not found, the logging code will use a normal
  40 // MessageBox, potentially causing the problems discussed above.
  41
  42
  43 // Instructions
  44 // ------------
  45 //
  46 // Make a bunch of macros for logging.  The way to log things is to stream
  47 // things to LOG(<a particular severity level>).  E.g.,
  48 //
  49 //   LOG(INFO) << "Found " << num_cookies << " cookies";
  50 //
  51 // You can also do conditional logging:
  52 //
  53 //   LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
  54 //
  55 // The CHECK(condition) macro is active in both debug and release builds and
  56 // effectively performs a LOG(FATAL) which terminates the process and
  57 // generates a crashdump unless a debugger is attached.
  58 //
  59 // There are also "debug mode" logging macros like the ones above:
  60 //
  61 //   DLOG(INFO) << "Found cookies";
  62 //
  63 //   DLOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
  64 //
  65 // All "debug mode" logging is compiled away to nothing for non-debug mode
  66 // compiles.  LOG_IF and development flags also work well together
  67 // because the code can be compiled away sometimes.
  68 //
  69 // We also have
  70 //
  71 //   LOG_ASSERT(assertion);
  72 //   DLOG_ASSERT(assertion);
  73 //
  74 // which is syntactic sugar for {,D}LOG_IF(FATAL, assert fails) << assertion;
  75 //
  76 // There are "verbose level" logging macros.  They look like
  77 //
  78 //   VLOG(1) << "I'm printed when you run the program with --v=1 or more";
  79 //   VLOG(2) << "I'm printed when you run the program with --v=2 or more";
  80 //
  81 // These always log at the INFO log level (when they log at all).
  82 // The verbose logging can also be turned on module-by-module.  For instance,
  83 //    --vmodule=profile=2,icon_loader=1,browser_*=3,*/chromeos/*=4 --v=0
  84 // will cause:
  85 //   a. VLOG(2) and lower messages to be printed from profile.{h,cc}
  86 //   b. VLOG(1) and lower messages to be printed from icon_loader.{h,cc}
  87 //   c. VLOG(3) and lower messages to be printed from files prefixed with
  88 //      "browser"
  89 //   d. VLOG(4) and lower messages to be printed from files under a
  90 //     "chromeos" directory.
  91 //   e. VLOG(0) and lower messages to be printed from elsewhere
  92 //
  93 // The wildcarding functionality shown by (c) supports both '*' (match
  94 // 0 or more characters) and '?' (match any single character)
  95 // wildcards.  Any pattern containing a forward or backward slash will
  96 // be tested against the whole pathname and not just the module.
  97 // E.g., "*/foo/bar/*=2" would change the logging level for all code
  98 // in source files under a "foo/bar" directory.
  99 //
 100 // There's also VLOG_IS_ON(n) "verbose level" condition macro. To be used as
 101 //
 102 //   if (VLOG_IS_ON(2)) {
 103 //     // do some logging preparation and logging
 104 //     // that can't be accomplished with just VLOG(2) << ...;
 105 //   }
 106 //
 107 // There is also a VLOG_IF "verbose level" condition macro for sample
 108 // cases, when some extra computation and preparation for logs is not
 109 // needed.
 110 //
 111 //   VLOG_IF(1, (size > 1024))
 112 //      << "I'm printed when size is more than 1024 and when you run the "
 113 //         "program with --v=1 or more";
 114 //
 115 // We also override the standard 'assert' to use 'DLOG_ASSERT'.
 116 //
 117 // Lastly, there is:
 118 //
 119 //   PLOG(ERROR) << "Couldn't do foo";
 120 //   DPLOG(ERROR) << "Couldn't do foo";
 121 //   PLOG_IF(ERROR, cond) << "Couldn't do foo";
 122 //   DPLOG_IF(ERROR, cond) << "Couldn't do foo";
 123 //   PCHECK(condition) << "Couldn't do foo";
 124 //   DPCHECK(condition) << "Couldn't do foo";
 125 //
 126 // which append the last system error to the message in string form (taken from
 127 // GetLastError() on Windows and errno on POSIX).
 128 //
 129 // The supported severity levels for macros that allow you to specify one
 130 // are (in increasing order of severity) INFO, WARNING, ERROR, ERROR_REPORT,
 131 // and FATAL.
 132 //
 133 // Very important: logging a message at the FATAL severity level causes
 134 // the program to terminate (after the message is logged).
 135 //
 136 // Note the special severity of ERROR_REPORT only available/relevant in normal
 137 // mode, which displays error dialog without terminating the program. There is
 138 // no error dialog for severity ERROR or below in normal mode.
 139 //
 140 // There is also the special severity of DFATAL, which logs FATAL in
 141 // debug mode, ERROR in normal mode.
 142
 143 namespace logging {
 144
 145 // TODO(avi): do we want to do a unification of character types here?
 146 #if defined(OS_WIN)
 147 typedef wchar_t PathChar;
 148 #else
 149 typedef char PathChar;
 150 #endif
 151
 152 // Where to record logging output? A flat file and/or system debug log
 153 // via OutputDebugString.
 154 enum LoggingDestination {
 155   LOG_NONE                = 0,
 156   LOG_TO_FILE             = 1 << 0,
 157   LOG_TO_SYSTEM_DEBUG_LOG = 1 << 1,
 158
 159   LOG_TO_ALL = LOG_TO_FILE | LOG_TO_SYSTEM_DEBUG_LOG,
 160
 161   // On Windows, use a file next to the exe; on POSIX platforms, where
 162   // it may not even be possible to locate the executable on disk, use
 163   // stderr.
 164 #if defined(OS_WIN)
 165   LOG_DEFAULT = LOG_TO_FILE,
 166 #elif defined(OS_POSIX)
 167   LOG_DEFAULT = LOG_TO_SYSTEM_DEBUG_LOG,
 168 #endif
 169 };
 170
 171 // Indicates that the log file should be locked when being written to.
 172 // Unless there is only one single-threaded process that is logging to
 173 // the log file, the file should be locked during writes to make each
 174 // log output atomic. Other writers will block.
 175 //
 176 // All processes writing to the log file must have their locking set for it to
 177 // work properly. Defaults to LOCK_LOG_FILE.
 178 enum LogLockingState { LOCK_LOG_FILE, DONT_LOCK_LOG_FILE };
 179
 180 // On startup, should we delete or append to an existing log file (if any)?
 181 // Defaults to APPEND_TO_OLD_LOG_FILE.
 182 enum OldFileDeletionState { DELETE_OLD_LOG_FILE, APPEND_TO_OLD_LOG_FILE };
 183
 184 struct BASE_EXPORT LoggingSettings {
 185   // The defaults values are:
 186   //
 187   //  logging_dest: LOG_DEFAULT
 188   //  log_file:     NULL
 189   //  lock_log:     LOCK_LOG_FILE
 190   //  delete_old:   APPEND_TO_OLD_LOG_FILE
 191   LoggingSettings();
 192
 193   LoggingDestination logging_dest;
 194
 195   // The three settings below have an effect only when LOG_TO_FILE is
 196   // set in |logging_dest|.
 197   const PathChar* log_file;
 198   LogLockingState lock_log;
 199   OldFileDeletionState delete_old;
 200 };
 201
 202 // Define different names for the BaseInitLoggingImpl() function depending on
 203 // whether NDEBUG is defined or not so that we'll fail to link if someone tries
 204 // to compile logging.cc with NDEBUG but includes logging.h without defining it,
 205 // or vice versa.
 206 #if NDEBUG
 207 #define BaseInitLoggingImpl BaseInitLoggingImpl_built_with_NDEBUG
 208 #else
 209 #define BaseInitLoggingImpl BaseInitLoggingImpl_built_without_NDEBUG
 210 #endif
 211
 212 // Implementation of the InitLogging() method declared below.  We use a
 213 // more-specific name so we can #define it above without affecting other code
 214 // that has named stuff "InitLogging".
 215 BASE_EXPORT bool BaseInitLoggingImpl(const LoggingSettings& settings);
 216
 217 // Sets the log file name and other global logging state. Calling this function
 218 // is recommended, and is normally done at the beginning of application init.
 219 // If you don't call it, all the flags will be initialized to their default
 220 // values, and there is a race condition that may leak a critical section
 221 // object if two threads try to do the first log at the same time.
 222 // See the definition of the enums above for descriptions and default values.
 223 //
 224 // The default log file is initialized to "debug.log" in the application
 225 // directory. You probably don't want this, especially since the program
 226 // directory may not be writable on an enduser's system.
 227 //
 228 // This function may be called a second time to re-direct logging (e.g after
 229 // loging in to a user partition), however it should never be called more than
 230 // twice.
 231 inline bool InitLogging(const LoggingSettings& settings) {
 232   return BaseInitLoggingImpl(settings);
 233 }
 234
 235 // Sets the log level. Anything at or above this level will be written to the
 236 // log file/displayed to the user (if applicable). Anything below this level
 237 // will be silently ignored. The log level defaults to 0 (everything is logged
 238 // up to level INFO) if this function is not called.
 239 // Note that log messages for VLOG(x) are logged at level -x, so setting
 240 // the min log level to negative values enables verbose logging.
 241 BASE_EXPORT void SetMinLogLevel(int level);
 242
 243 // Gets the current log level.
 244 BASE_EXPORT int GetMinLogLevel();
 245
 246 // Gets the VLOG default verbosity level.
 247 BASE_EXPORT int GetVlogVerbosity();
 248
 249 // Gets the current vlog level for the given file (usually taken from
 250 // __FILE__).
 251
 252 // Note that |N| is the size *with* the null terminator.
 253 BASE_EXPORT int GetVlogLevelHelper(const char* file_start, size_t N);
 254
 255 template <size_t N>
 256 int GetVlogLevel(const char (&file)[N]) {
 257   return GetVlogLevelHelper(file, N);
 258 }
 259
 260 // Sets the common items you want to be prepended to each log message.
 261 // process and thread IDs default to off, the timestamp defaults to on.
 262 // If this function is not called, logging defaults to writing the timestamp
 263 // only.
 264 BASE_EXPORT void SetLogItems(bool enable_process_id, bool enable_thread_id,
 265                              bool enable_timestamp, bool enable_tickcount);
 266
 267 // Sets whether or not you'd like to see fatal debug messages popped up in
 268 // a dialog box or not.
 269 // Dialogs are not shown by default.
 270 BASE_EXPORT void SetShowErrorDialogs(bool enable_dialogs);
 271
 272 // Sets the Log Assert Handler that will be used to notify of check failures.
 273 // The default handler shows a dialog box and then terminate the process,
 274 // however clients can use this function to override with their own handling
 275 // (e.g. a silent one for Unit Tests)
 276 typedef void (*LogAssertHandlerFunction)(const std::string& str);
 277 BASE_EXPORT void SetLogAssertHandler(LogAssertHandlerFunction handler);
 278
 279 // Sets the Log Report Handler that will be used to notify of check failures
 280 // in non-debug mode. The default handler shows a dialog box and continues
 281 // the execution, however clients can use this function to override with their
 282 // own handling.
 283 typedef void (*LogReportHandlerFunction)(const std::string& str);
 284 BASE_EXPORT void SetLogReportHandler(LogReportHandlerFunction handler);
 285
 286 // Sets the Log Message Handler that gets passed every log message before
 287 // it's sent to other log destinations (if any).
 288 // Returns true to signal that it handled the message and the message
 289 // should not be sent to other log destinations.
 290 typedef bool (*LogMessageHandlerFunction)(int severity,
 291     const char* file, int line, size_t message_start, const std::string& str);
 292 BASE_EXPORT void SetLogMessageHandler(LogMessageHandlerFunction handler);
 293 BASE_EXPORT LogMessageHandlerFunction GetLogMessageHandler();
 294
 295 typedef int LogSeverity;
 296 const LogSeverity LOG_VERBOSE = -1;  // This is level 1 verbosity
 297 // Note: the log severities are used to index into the array of names,
 298 // see log_severity_names.
 299 const LogSeverity LOG_INFO = 0;
 300 const LogSeverity LOG_WARNING = 1;
 301 const LogSeverity LOG_ERROR = 2;
 302 const LogSeverity LOG_ERROR_REPORT = 3;
 303 const LogSeverity LOG_FATAL = 4;
 304 const LogSeverity LOG_NUM_SEVERITIES = 5;
 305
 306 // LOG_DFATAL is LOG_FATAL in debug mode, ERROR in normal mode
 307 #ifdef NDEBUG
 308 const LogSeverity LOG_DFATAL = LOG_ERROR;
 309 #else
 310 const LogSeverity LOG_DFATAL = LOG_FATAL;
 311 #endif
 312
 313 // A few definitions of macros that don't generate much code. These are used
 314 // by LOG() and LOG_IF, etc. Since these are used all over our code, it's
 315 // better to have compact code for these operations.
 316 #define COMPACT_GOOGLE_LOG_EX_INFO(ClassName, ...) \
 317   logging::ClassName(__FILE__, __LINE__, logging::LOG_INFO , ##__VA_ARGS__)
 318 #define COMPACT_GOOGLE_LOG_EX_WARNING(ClassName, ...) \
 319   logging::ClassName(__FILE__, __LINE__, logging::LOG_WARNING , ##__VA_ARGS__)
 320 #define COMPACT_GOOGLE_LOG_EX_ERROR(ClassName, ...) \
 321   logging::ClassName(__FILE__, __LINE__, logging::LOG_ERROR , ##__VA_ARGS__)
 322 #define COMPACT_GOOGLE_LOG_EX_ERROR_REPORT(ClassName, ...) \
 323   logging::ClassName(__FILE__, __LINE__, \
 324                      logging::LOG_ERROR_REPORT , ##__VA_ARGS__)
 325 #define COMPACT_GOOGLE_LOG_EX_FATAL(ClassName, ...) \
 326   logging::ClassName(__FILE__, __LINE__, logging::LOG_FATAL , ##__VA_ARGS__)
 327 #define COMPACT_GOOGLE_LOG_EX_DFATAL(ClassName, ...) \
 328   logging::ClassName(__FILE__, __LINE__, logging::LOG_DFATAL , ##__VA_ARGS__)
 329
 330 #define COMPACT_GOOGLE_LOG_INFO \
 331   COMPACT_GOOGLE_LOG_EX_INFO(LogMessage)
 332 #define COMPACT_GOOGLE_LOG_WARNING \
 333   COMPACT_GOOGLE_LOG_EX_WARNING(LogMessage)
 334 #define COMPACT_GOOGLE_LOG_ERROR \
 335   COMPACT_GOOGLE_LOG_EX_ERROR(LogMessage)
 336 #define COMPACT_GOOGLE_LOG_ERROR_REPORT \
 337   COMPACT_GOOGLE_LOG_EX_ERROR_REPORT(LogMessage)
 338 #define COMPACT_GOOGLE_LOG_FATAL \
 339   COMPACT_GOOGLE_LOG_EX_FATAL(LogMessage)
 340 #define COMPACT_GOOGLE_LOG_DFATAL \
 341   COMPACT_GOOGLE_LOG_EX_DFATAL(LogMessage)
 342
 343 #if defined(OS_WIN)
 344 // wingdi.h defines ERROR to be 0. When we call LOG(ERROR), it gets
 345 // substituted with 0, and it expands to COMPACT_GOOGLE_LOG_0. To allow us
 346 // to keep using this syntax, we define this macro to do the same thing
 347 // as COMPACT_GOOGLE_LOG_ERROR, and also define ERROR the same way that
 348 // the Windows SDK does for consistency.
 349 #define ERROR 0
 350 #define COMPACT_GOOGLE_LOG_EX_0(ClassName, ...) \
 351   COMPACT_GOOGLE_LOG_EX_ERROR(ClassName , ##__VA_ARGS__)
 352 #define COMPACT_GOOGLE_LOG_0 COMPACT_GOOGLE_LOG_ERROR
 353 // Needed for LOG_IS_ON(ERROR).
 354 const LogSeverity LOG_0 = LOG_ERROR;
 355 #endif
 356
 357 // As special cases, we can assume that LOG_IS_ON(ERROR_REPORT) and
 358 // LOG_IS_ON(FATAL) always hold.  Also, LOG_IS_ON(DFATAL) always holds
 359 // in debug mode.  In particular, CHECK()s will always fire if they
 360 // fail.
 361 #define LOG_IS_ON(severity) \
 362   ((::logging::LOG_ ## severity) >= ::logging::GetMinLogLevel())
 363
 364 // We can't do any caching tricks with VLOG_IS_ON() like the
 365 // google-glog version since it requires GCC extensions.  This means
 366 // that using the v-logging functions in conjunction with --vmodule
 367 // may be slow.
 368 #define VLOG_IS_ON(verboselevel) \
 369   ((verboselevel) <= ::logging::GetVlogLevel(__FILE__))
 370
 371 // Helper macro which avoids evaluating the arguments to a stream if
 372 // the condition doesn't hold.
 373 #define LAZY_STREAM(stream, condition)                                  \
 374   !(condition) ? (void) 0 : ::logging::LogMessageVoidify() & (stream)
 375
 376 // We use the preprocessor's merging operator, "##", so that, e.g.,
 377 // LOG(INFO) becomes the token COMPACT_GOOGLE_LOG_INFO.  There's some funny
 378 // subtle difference between ostream member streaming functions (e.g.,
 379 // ostream::operator<<(int) and ostream non-member streaming functions
 380 // (e.g., ::operator<<(ostream&, string&): it turns out that it's
 381 // impossible to stream something like a string directly to an unnamed
 382 // ostream. We employ a neat hack by calling the stream() member
 383 // function of LogMessage which seems to avoid the problem.
 384 #define LOG_STREAM(severity) COMPACT_GOOGLE_LOG_ ## severity.stream()
 385
 386 #define LOG(severity) LAZY_STREAM(LOG_STREAM(severity), LOG_IS_ON(severity))
 387 #define LOG_IF(severity, condition) \
 388   LAZY_STREAM(LOG_STREAM(severity), LOG_IS_ON(severity) && (condition))
 389
 390 #define SYSLOG(severity) LOG(severity)
 391 #define SYSLOG_IF(severity, condition) LOG_IF(severity, condition)
 392
 393 // The VLOG macros log with negative verbosities.
 394 #define VLOG_STREAM(verbose_level) \
 395   logging::LogMessage(__FILE__, __LINE__, -verbose_level).stream()
 396
 397 #define VLOG(verbose_level) \
 398   LAZY_STREAM(VLOG_STREAM(verbose_level), VLOG_IS_ON(verbose_level))
 399
 400 #define VLOG_IF(verbose_level, condition) \
 401   LAZY_STREAM(VLOG_STREAM(verbose_level), \
 402       VLOG_IS_ON(verbose_level) && (condition))
 403
 404 #if defined (OS_WIN)
 405 #define VPLOG_STREAM(verbose_level) \
 406   logging::Win32ErrorLogMessage(__FILE__, __LINE__, -verbose_level, \
 407     ::logging::GetLastSystemErrorCode()).stream()
 408 #elif defined(OS_POSIX)
 409 #define VPLOG_STREAM(verbose_level) \
 410   logging::ErrnoLogMessage(__FILE__, __LINE__, -verbose_level, \
 411     ::logging::GetLastSystemErrorCode()).stream()
 412 #endif
 413
 414 #define VPLOG(verbose_level) \
 415   LAZY_STREAM(VPLOG_STREAM(verbose_level), VLOG_IS_ON(verbose_level))
 416
 417 #define VPLOG_IF(verbose_level, condition) \
 418   LAZY_STREAM(VPLOG_STREAM(verbose_level), \
 419     VLOG_IS_ON(verbose_level) && (condition))
 420
 421 // TODO(akalin): Add more VLOG variants, e.g. VPLOG.
 422
 423 #define LOG_ASSERT(condition)  \
 424   LOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "
 425 #define SYSLOG_ASSERT(condition) \
 426   SYSLOG_IF(FATAL, !(condition)) << "Assert failed: " #condition ". "
 427
 428 #if defined(OS_WIN)
 429 #define PLOG_STREAM(severity) \
 430   COMPACT_GOOGLE_LOG_EX_ ## severity(Win32ErrorLogMessage, \
 431       ::logging::GetLastSystemErrorCode()).stream()
 432 #elif defined(OS_POSIX)
 433 #define PLOG_STREAM(severity) \
 434   COMPACT_GOOGLE_LOG_EX_ ## severity(ErrnoLogMessage, \
 435       ::logging::GetLastSystemErrorCode()).stream()
 436 #endif
 437
 438 #define PLOG(severity)                                          \
 439   LAZY_STREAM(PLOG_STREAM(severity), LOG_IS_ON(severity))
 440
 441 #define PLOG_IF(severity, condition) \
 442   LAZY_STREAM(PLOG_STREAM(severity), LOG_IS_ON(severity) && (condition))
 443
 444 // The actual stream used isn't important.
 445 #define EAT_STREAM_PARAMETERS                                           \
 446   true ? (void) 0 : ::logging::LogMessageVoidify() & LOG_STREAM(FATAL)
 447
 448 // CHECK dies with a fatal error if condition is not true.  It is *not*
 449 // controlled by NDEBUG, so the check will be executed regardless of
 450 // compilation mode.
 451 //
 452 // We make sure CHECK et al. always evaluates their arguments, as
 453 // doing CHECK(FunctionWithSideEffect()) is a common idiom.
 454
 455 #if defined(OFFICIAL_BUILD) && defined(NDEBUG)
 456
 457 // Make all CHECK functions discard their log strings to reduce code
 458 // bloat for official release builds.
 459
 460 // TODO(akalin): This would be more valuable if there were some way to
 461 // remove BreakDebugger() from the backtrace, perhaps by turning it
 462 // into a macro (like __debugbreak() on Windows).
 463 #define CHECK(condition)                                                \
 464   !(condition) ? ::base::debug::BreakDebugger() : EAT_STREAM_PARAMETERS
 465
 466 #define PCHECK(condition) CHECK(condition)
 467
 468 #define CHECK_OP(name, op, val1, val2) CHECK((val1) op (val2))
 469
 470 #else
 471
 472 #define CHECK(condition)                       \
 473   LAZY_STREAM(LOG_STREAM(FATAL), !(condition)) \
 474   << "Check failed: " #condition ". "
 475
 476 #define PCHECK(condition) \
 477   LAZY_STREAM(PLOG_STREAM(FATAL), !(condition)) \
 478   << "Check failed: " #condition ". "
 479
 480 // Helper macro for binary operators.
 481 // Don't use this macro directly in your code, use CHECK_EQ et al below.
 482 //
 483 // TODO(akalin): Rewrite this so that constructs like if (...)
 484 // CHECK_EQ(...) else { ... } work properly.
 485 #define CHECK_OP(name, op, val1, val2)                          \
 486   if (std::string* _result =                                    \
 487       logging::Check##name##Impl((val1), (val2),                \
 488                                  #val1 " " #op " " #val2))      \
 489     logging::LogMessage(__FILE__, __LINE__, _result).stream()
 490
 491 #endif
 492
 493 // Build the error message string.  This is separate from the "Impl"
 494 // function template because it is not performance critical and so can
 495 // be out of line, while the "Impl" code should be inline.  Caller
 496 // takes ownership of the returned string.
 497 template<class t1, class t2>
 498 std::string* MakeCheckOpString(const t1& v1, const t2& v2, const char* names) {
 499   std::ostringstream ss;
 500   ss << names << " (" << v1 << " vs. " << v2 << ")";
 501   std::string* msg = new std::string(ss.str());
 502   return msg;
 503 }
 504
 505 // MSVC doesn't like complex extern templates and DLLs.
 506 #if !defined(COMPILER_MSVC)
 507 // Commonly used instantiations of MakeCheckOpString<>. Explicitly instantiated
 508 // in logging.cc.
 509 extern template BASE_EXPORT std::string* MakeCheckOpString<int, int>(
 510     const int&, const int&, const char* names);
 511 extern template BASE_EXPORT
 512 std::string* MakeCheckOpString<unsigned long, unsigned long>(
 513     const unsigned long&, const unsigned long&, const char* names);
 514 extern template BASE_EXPORT
 515 std::string* MakeCheckOpString<unsigned long, unsigned int>(
 516     const unsigned long&, const unsigned int&, const char* names);
 517 extern template BASE_EXPORT
 518 std::string* MakeCheckOpString<unsigned int, unsigned long>(
 519     const unsigned int&, const unsigned long&, const char* names);
 520 extern template BASE_EXPORT
 521 std::string* MakeCheckOpString<std::string, std::string>(
 522     const std::string&, const std::string&, const char* name);
 523 #endif
 524
 525 // Helper functions for CHECK_OP macro.
 526 // The (int, int) specialization works around the issue that the compiler
 527 // will not instantiate the template version of the function on values of
 528 // unnamed enum type - see comment below.
 529 #define DEFINE_CHECK_OP_IMPL(name, op) \
 530   template <class t1, class t2> \
 531   inline std::string* Check##name##Impl(const t1& v1, const t2& v2, \
 532                                         const char* names) { \
 533     if (v1 op v2) return NULL; \
 534     else return MakeCheckOpString(v1, v2, names); \
 535   } \
 536   inline std::string* Check##name##Impl(int v1, int v2, const char* names) { \
 537     if (v1 op v2) return NULL; \
 538     else return MakeCheckOpString(v1, v2, names); \
 539   }
 540 DEFINE_CHECK_OP_IMPL(EQ, ==)
 541 DEFINE_CHECK_OP_IMPL(NE, !=)
 542 DEFINE_CHECK_OP_IMPL(LE, <=)
 543 DEFINE_CHECK_OP_IMPL(LT, < )
 544 DEFINE_CHECK_OP_IMPL(GE, >=)
 545 DEFINE_CHECK_OP_IMPL(GT, > )
 546 #undef DEFINE_CHECK_OP_IMPL
 547
 548 #define CHECK_EQ(val1, val2) CHECK_OP(EQ, ==, val1, val2)
 549 #define CHECK_NE(val1, val2) CHECK_OP(NE, !=, val1, val2)
 550 #define CHECK_LE(val1, val2) CHECK_OP(LE, <=, val1, val2)
 551 #define CHECK_LT(val1, val2) CHECK_OP(LT, < , val1, val2)
 552 #define CHECK_GE(val1, val2) CHECK_OP(GE, >=, val1, val2)
 553 #define CHECK_GT(val1, val2) CHECK_OP(GT, > , val1, val2)
 554
 555 #if defined(NDEBUG)
 556 #define ENABLE_DLOG 0
 557 #else
 558 #define ENABLE_DLOG 1
 559 #endif
 560
 561 #if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
 562 #define DCHECK_IS_ON 0
 563 #else
 564 #define DCHECK_IS_ON 1
 565 #endif
 566
 567 // Definitions for DLOG et al.
 568
 569 #if ENABLE_DLOG
 570
 571 #define DLOG_IS_ON(severity) LOG_IS_ON(severity)
 572 #define DLOG_IF(severity, condition) LOG_IF(severity, condition)
 573 #define DLOG_ASSERT(condition) LOG_ASSERT(condition)
 574 #define DPLOG_IF(severity, condition) PLOG_IF(severity, condition)
 575 #define DVLOG_IF(verboselevel, condition) VLOG_IF(verboselevel, condition)
 576 #define DVPLOG_IF(verboselevel, condition) VPLOG_IF(verboselevel, condition)
 577
 578 #else  // ENABLE_DLOG
 579
 580 // If ENABLE_DLOG is off, we want to avoid emitting any references to
 581 // |condition| (which may reference a variable defined only if NDEBUG
 582 // is not defined).  Contrast this with DCHECK et al., which has
 583 // different behavior.
 584
 585 #define DLOG_IS_ON(severity) false
 586 #define DLOG_IF(severity, condition) EAT_STREAM_PARAMETERS
 587 #define DLOG_ASSERT(condition) EAT_STREAM_PARAMETERS
 588 #define DPLOG_IF(severity, condition) EAT_STREAM_PARAMETERS
 589 #define DVLOG_IF(verboselevel, condition) EAT_STREAM_PARAMETERS
 590 #define DVPLOG_IF(verboselevel, condition) EAT_STREAM_PARAMETERS
 591
 592 #endif  // ENABLE_DLOG
 593
 594 // DEBUG_MODE is for uses like
 595 //   if (DEBUG_MODE) foo.CheckThatFoo();
 596 // instead of
 597 //   #ifndef NDEBUG
 598 //     foo.CheckThatFoo();
 599 //   #endif
 600 //
 601 // We tie its state to ENABLE_DLOG.
 602 enum { DEBUG_MODE = ENABLE_DLOG };
 603
 604 #undef ENABLE_DLOG
 605
 606 #define DLOG(severity)                                          \
 607   LAZY_STREAM(LOG_STREAM(severity), DLOG_IS_ON(severity))
 608
 609 #define DPLOG(severity)                                         \
 610   LAZY_STREAM(PLOG_STREAM(severity), DLOG_IS_ON(severity))
 611
 612 #define DVLOG(verboselevel) DVLOG_IF(verboselevel, VLOG_IS_ON(verboselevel))
 613
 614 #define DVPLOG(verboselevel) DVPLOG_IF(verboselevel, VLOG_IS_ON(verboselevel))
 615
 616 // TODO(vitalybuka): following should be removed and replaced with PLOG.
 617 #if defined(OS_WIN)
 618 #define LOG_GETLASTERROR(severity) PLOG(severity)
 619 #define DLOG_GETLASTERROR(severity) DPLOG(severity)
 620 #elif defined(OS_POSIX)
 621 #define LOG_ERRNO(severity) PLOG(severity)
 622 #define DLOG_ERRNO(severity) DPLOG(severity)
 623 #endif
 624
 625 // Definitions for DCHECK et al.
 626
 627 #if DCHECK_IS_ON
 628
 629 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \
 630   COMPACT_GOOGLE_LOG_EX_FATAL(ClassName , ##__VA_ARGS__)
 631 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_FATAL
 632 const LogSeverity LOG_DCHECK = LOG_FATAL;
 633
 634 #else  // DCHECK_IS_ON
 635
 636 // These are just dummy values.
 637 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \
 638   COMPACT_GOOGLE_LOG_EX_INFO(ClassName , ##__VA_ARGS__)
 639 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_INFO
 640 const LogSeverity LOG_DCHECK = LOG_INFO;
 641
 642 #endif  // DCHECK_IS_ON
 643
 644 // DCHECK et al. make sure to reference |condition| regardless of
 645 // whether DCHECKs are enabled; this is so that we don't get unused
 646 // variable warnings if the only use of a variable is in a DCHECK.
 647 // This behavior is different from DLOG_IF et al.
 648
 649 #define DCHECK(condition)                                         \
 650   LAZY_STREAM(LOG_STREAM(DCHECK), DCHECK_IS_ON && !(condition))   \
 651   << "Check failed: " #condition ". "
 652
 653 #define DPCHECK(condition)                                        \
 654   LAZY_STREAM(PLOG_STREAM(DCHECK), DCHECK_IS_ON && !(condition))  \
 655   << "Check failed: " #condition ". "
 656
 657 // Helper macro for binary operators.
 658 // Don't use this macro directly in your code, use DCHECK_EQ et al below.
 659 #define DCHECK_OP(name, op, val1, val2)                         \
 660   if (DCHECK_IS_ON)                                             \
 661     if (std::string* _result =                                  \
 662         logging::Check##name##Impl((val1), (val2),              \
 663                                    #val1 " " #op " " #val2))    \
 664       logging::LogMessage(                                      \
 665           __FILE__, __LINE__, ::logging::LOG_DCHECK,            \
 666           _result).stream()
 667
 668 // Equality/Inequality checks - compare two values, and log a
 669 // LOG_DCHECK message including the two values when the result is not
 670 // as expected.  The values must have operator<<(ostream, ...)
 671 // defined.
 672 //
 673 // You may append to the error message like so:
 674 //   DCHECK_NE(1, 2) << ": The world must be ending!";
 675 //
 676 // We are very careful to ensure that each argument is evaluated exactly
 677 // once, and that anything which is legal to pass as a function argument is
 678 // legal here.  In particular, the arguments may be temporary expressions
 679 // which will end up being destroyed at the end of the apparent statement,
 680 // for example:
 681 //   DCHECK_EQ(string("abc")[1], 'b');
 682 //
 683 // WARNING: These may not compile correctly if one of the arguments is a pointer
 684 // and the other is NULL. To work around this, simply static_cast NULL to the
 685 // type of the desired pointer.
 686
 687 #define DCHECK_EQ(val1, val2) DCHECK_OP(EQ, ==, val1, val2)
 688 #define DCHECK_NE(val1, val2) DCHECK_OP(NE, !=, val1, val2)
 689 #define DCHECK_LE(val1, val2) DCHECK_OP(LE, <=, val1, val2)
 690 #define DCHECK_LT(val1, val2) DCHECK_OP(LT, < , val1, val2)
 691 #define DCHECK_GE(val1, val2) DCHECK_OP(GE, >=, val1, val2)
 692 #define DCHECK_GT(val1, val2) DCHECK_OP(GT, > , val1, val2)
 693
 694 #if defined(NDEBUG) && defined(OS_CHROMEOS)
 695 #define NOTREACHED() LOG(ERROR) << "NOTREACHED() hit in " << \
 696     __FUNCTION__ << ". "
 697 #else
 698 #define NOTREACHED() DCHECK(false)
 699 #endif
 700
 701 // Redefine the standard assert to use our nice log files
 702 #undef assert
 703 #define assert(x) DLOG_ASSERT(x)
 704
 705 // This class more or less represents a particular log message.  You
 706 // create an instance of LogMessage and then stream stuff to it.
 707 // When you finish streaming to it, ~LogMessage is called and the
 708 // full message gets streamed to the appropriate destination.
 709 //
 710 // You shouldn't actually use LogMessage's constructor to log things,
 711 // though.  You should use the LOG() macro (and variants thereof)
 712 // above.
 713 class BASE_EXPORT LogMessage {
 714  public:
 715   LogMessage(const char* file, int line, LogSeverity severity, int ctr);
 716
 717   // Two special constructors that generate reduced amounts of code at
 718   // LOG call sites for common cases.
 719   //
 720   // Used for LOG(INFO): Implied are:
 721   // severity = LOG_INFO, ctr = 0
 722   //
 723   // Using this constructor instead of the more complex constructor above
 724   // saves a couple of bytes per call site.
 725   LogMessage(const char* file, int line);
 726
 727   // Used for LOG(severity) where severity != INFO.  Implied
 728   // are: ctr = 0
 729   //
 730   // Using this constructor instead of the more complex constructor above
 731   // saves a couple of bytes per call site.
 732   LogMessage(const char* file, int line, LogSeverity severity);
 733
 734   // A special constructor used for check failures.  Takes ownership
 735   // of the given string.
 736   // Implied severity = LOG_FATAL
 737   LogMessage(const char* file, int line, std::string* result);
 738
 739   // A special constructor used for check failures, with the option to
 740   // specify severity.  Takes ownership of the given string.
 741   LogMessage(const char* file, int line, LogSeverity severity,
 742              std::string* result);
 743
 744   ~LogMessage();
 745
 746   std::ostream& stream() { return stream_; }
 747
 748  private:
 749   void Init(const char* file, int line);
 750
 751   LogSeverity severity_;
 752   std::ostringstream stream_;
 753   size_t message_start_;  // Offset of the start of the message (past prefix
 754                           // info).
 755   // The file and line information passed in to the constructor.
 756   const char* file_;
 757   const int line_;
 758
 759 #if defined(OS_WIN)
 760   // Stores the current value of GetLastError in the constructor and restores
 761   // it in the destructor by calling SetLastError.
 762   // This is useful since the LogMessage class uses a lot of Win32 calls
 763   // that will lose the value of GLE and the code that called the log function
 764   // will have lost the thread error value when the log call returns.
 765   class SaveLastError {
 766    public:
 767     SaveLastError();
 768     ~SaveLastError();
 769
 770     unsigned long get_error() const { return last_error_; }
 771
 772    protected:
 773     unsigned long last_error_;
 774   };
 775
 776   SaveLastError last_error_;
 777 #endif
 778
 779   DISALLOW_COPY_AND_ASSIGN(LogMessage);
 780 };
 781
 782 // A non-macro interface to the log facility; (useful
 783 // when the logging level is not a compile-time constant).
 784 inline void LogAtLevel(int const log_level, std::string const &msg) {
 785   LogMessage(__FILE__, __LINE__, log_level).stream() << msg;
 786 }
 787
 788 // This class is used to explicitly ignore values in the conditional
 789 // logging macros.  This avoids compiler warnings like "value computed
 790 // is not used" and "statement has no effect".
 791 class LogMessageVoidify {
 792  public:
 793   LogMessageVoidify() { }
 794   // This has to be an operator with a precedence lower than << but
 795   // higher than ?:
 796   void operator&(std::ostream&) { }
 797 };
 798
 799 #if defined(OS_WIN)
 800 typedef unsigned long SystemErrorCode;
 801 #elif defined(OS_POSIX)
 802 typedef int SystemErrorCode;
 803 #endif
 804
 805 // Alias for ::GetLastError() on Windows and errno on POSIX. Avoids having to
 806 // pull in windows.h just for GetLastError() and DWORD.
 807 BASE_EXPORT SystemErrorCode GetLastSystemErrorCode();
 808 BASE_EXPORT std::string SystemErrorCodeToString(SystemErrorCode error_code);
 809
 810 #if defined(OS_WIN)
 811 // Appends a formatted system message of the GetLastError() type.
 812 class BASE_EXPORT Win32ErrorLogMessage {
 813  public:
 814   Win32ErrorLogMessage(const char* file,
 815                        int line,
 816                        LogSeverity severity,
 817                        SystemErrorCode err);
 818
 819   // Appends the error message before destructing the encapsulated class.
 820   ~Win32ErrorLogMessage();
 821
 822   std::ostream& stream() { return log_message_.stream(); }
 823
 824  private:
 825   SystemErrorCode err_;
 826   LogMessage log_message_;
 827
 828   DISALLOW_COPY_AND_ASSIGN(Win32ErrorLogMessage);
 829 };
 830 #elif defined(OS_POSIX)
 831 // Appends a formatted system message of the errno type
 832 class BASE_EXPORT ErrnoLogMessage {
 833  public:
 834   ErrnoLogMessage(const char* file,
 835                   int line,
 836                   LogSeverity severity,
 837                   SystemErrorCode err);
 838
 839   // Appends the error message before destructing the encapsulated class.
 840   ~ErrnoLogMessage();
 841
 842   std::ostream& stream() { return log_message_.stream(); }
 843
 844  private:
 845   SystemErrorCode err_;
 846   LogMessage log_message_;
 847
 848   DISALLOW_COPY_AND_ASSIGN(ErrnoLogMessage);
 849 };
 850 #endif  // OS_WIN
 851
 852 // Closes the log file explicitly if open.
 853 // NOTE: Since the log file is opened as necessary by the action of logging
 854 //       statements, there's no guarantee that it will stay closed
 855 //       after this call.
 856 BASE_EXPORT void CloseLogFile();
 857
 858 // Async signal safe logging mechanism.
 859 BASE_EXPORT void RawLog(int level, const char* message);
 860
 861 #define RAW_LOG(level, message) logging::RawLog(logging::LOG_ ## level, message)
 862
 863 #define RAW_CHECK(condition)                                                   \
 864   do {                                                                         \
 865     if (!(condition))                                                          \
 866       logging::RawLog(logging::LOG_FATAL, "Check failed: " #condition "\n");   \
 867   } while (0)
 868
 869 #if defined(OS_WIN)
 870 // Returns the default log file path.
 871 BASE_EXPORT std::wstring GetLogFileFullPath();
 872 #endif
 873
 874 }  // namespace logging
 875
 876 // These functions are provided as a convenience for logging, which is where we
 877 // use streams (it is against Google style to use streams in other places). It
 878 // is designed to allow you to emit non-ASCII Unicode strings to the log file,
 879 // which is normally ASCII. It is relatively slow, so try not to use it for
 880 // common cases. Non-ASCII characters will be converted to UTF-8 by these
 881 // operators.
 882 BASE_EXPORT std::ostream& operator<<(std::ostream& out, const wchar_t* wstr);
 883 inline std::ostream& operator<<(std::ostream& out, const std::wstring& wstr) {
 884   return out << wstr.c_str();
 885 }
 886
 887 // The NOTIMPLEMENTED() macro annotates codepaths which have
 888 // not been implemented yet.
 889 //
 890 // The implementation of this macro is controlled by NOTIMPLEMENTED_POLICY:
 891 //   0 -- Do nothing (stripped by compiler)
 892 //   1 -- Warn at compile time
 893 //   2 -- Fail at compile time
 894 //   3 -- Fail at runtime (DCHECK)
 895 //   4 -- [default] LOG(ERROR) at runtime
 896 //   5 -- LOG(ERROR) at runtime, only once per call-site
 897
 898 #ifndef NOTIMPLEMENTED_POLICY
 899 #if defined(OS_ANDROID) && defined(OFFICIAL_BUILD)
 900 #define NOTIMPLEMENTED_POLICY 0
 901 #else
 902 // Select default policy: LOG(ERROR)
 903 #define NOTIMPLEMENTED_POLICY 4
 904 #endif
 905 #endif
 906
 907 #if defined(COMPILER_GCC)
 908 // On Linux, with GCC, we can use __PRETTY_FUNCTION__ to get the demangled name
 909 // of the current function in the NOTIMPLEMENTED message.
 910 #define NOTIMPLEMENTED_MSG "Not implemented reached in " << __PRETTY_FUNCTION__
 911 #else
 912 #define NOTIMPLEMENTED_MSG "NOT IMPLEMENTED"
 913 #endif
 914
 915 #if NOTIMPLEMENTED_POLICY == 0
 916 #define NOTIMPLEMENTED() EAT_STREAM_PARAMETERS
 917 #elif NOTIMPLEMENTED_POLICY == 1
 918 // TODO, figure out how to generate a warning
 919 #define NOTIMPLEMENTED() COMPILE_ASSERT(false, NOT_IMPLEMENTED)
 920 #elif NOTIMPLEMENTED_POLICY == 2
 921 #define NOTIMPLEMENTED() COMPILE_ASSERT(false, NOT_IMPLEMENTED)
 922 #elif NOTIMPLEMENTED_POLICY == 3
 923 #define NOTIMPLEMENTED() NOTREACHED()
 924 #elif NOTIMPLEMENTED_POLICY == 4
 925 #define NOTIMPLEMENTED() LOG(ERROR) << NOTIMPLEMENTED_MSG
 926 #elif NOTIMPLEMENTED_POLICY == 5
 927 #define NOTIMPLEMENTED() do {\
 928   static bool logged_once = false;\
 929   LOG_IF(ERROR, !logged_once) << NOTIMPLEMENTED_MSG;\
 930   logged_once = true;\
 931 } while(0);\
 932 EAT_STREAM_PARAMETERS
 933 #endif
 934
 935 #endif  // BASE_LOGGING_H_