base/logging.h

Go to the documentation of this file.

// Copyright 2010-2021 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef OR_TOOLS_BASE_LOGGING_H_
#define OR_TOOLS_BASE_LOGGING_H_

#include <errno.h>
#include <string.h>
#include <time.h>

#include <cassert>
#include <cstddef>
#include <iosfwd>
#include <ostream>
#include <sstream>
#include <string>
#if defined(__GNUC__) && defined(__linux__)
#include <unistd.h>
#endif
#include <vector>

#include "ortools/base/commandlineflags.h"
#include "ortools/base/integral_types.h"
#include "ortools/base/log_severity.h"
#include "ortools/base/logging_export.h"
#include "ortools/base/macros.h"
#include "ortools/base/vlog_is_on.h"

#define QCHECK CHECK
#define QCHECK_EQ CHECK_EQ
#define ABSL_DIE_IF_NULL CHECK_NOTNULL
#define CHECK_OK(x) CHECK((x).ok())
#define QCHECK_OK CHECK_OK

// used by or-tools non C++ ports to bridge with the C++ layer.
void FixFlagsAndEnvironmentForSwig();

#if defined(_MSC_VER)
#define GLOG_MSVC_PUSH_DISABLE_WARNING(n) \
  __pragma(warning(push)) __pragma(warning(disable : n))
#define GLOG_MSVC_POP_WARNING() __pragma(warning(pop))
#define ATTRIBUTE_NOINLINE
#define ATTRIBUTE_NORETURN __declspec(noreturn)
#else
#define GLOG_MSVC_PUSH_DISABLE_WARNING(n)
#define GLOG_MSVC_POP_WARNING()
#define ATTRIBUTE_NOINLINE __attribute__((noinline))
#define ATTRIBUTE_NORETURN __attribute__((noreturn))
#endif

// The global value of GOOGLE_STRIP_LOG. All the messages logged to
// LOG(XXX) with severity less than GOOGLE_STRIP_LOG will not be displayed.
// If it can be determined at compile time that the message will not be
// printed, the statement will be compiled out.
//
// Example: to strip out all INFO and WARNING messages, use the value
// of 2 below. To make an exception for WARNING messages from a single
// file, add "#define GOOGLE_STRIP_LOG 1" to that file _before_ including
// base/logging.h
#ifndef GOOGLE_STRIP_LOG
#define GOOGLE_STRIP_LOG 0
#endif

// GCC can be told that a certain branch is not likely to be taken (for
// instance, a CHECK failure), and use that information in static analysis.
// Giving it this information can help it optimize for the common case in
// the absence of better information (ie. -fprofile-arcs).
//
#ifndef GOOGLE_PREDICT_BRANCH_NOT_TAKEN
#if !defined(_MSC_VER)
#define GOOGLE_PREDICT_BRANCH_NOT_TAKEN(x) (__builtin_expect(x, 0))
#else
#define GOOGLE_PREDICT_BRANCH_NOT_TAKEN(x) x
#endif
#endif

#ifndef GOOGLE_PREDICT_FALSE
#if !defined(_MSC_VER)
#define GOOGLE_PREDICT_FALSE(x) (__builtin_expect(x, 0))
#else
#define GOOGLE_PREDICT_FALSE(x) x
#endif
#endif

#ifndef GOOGLE_PREDICT_TRUE
#if !defined(_MSC_VER)
#define GOOGLE_PREDICT_TRUE(x) (__builtin_expect(!!(x), 1))
#else
#define GOOGLE_PREDICT_TRUE(x) x
#endif
#endif

// 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 capture log messages in a string, rather than reporting them
// immediately:
//
//   vector<string> errors;
//   LOG_STRING(ERROR, &errors) << "Couldn't parse cookie #" << cookie_num;
//
// This pushes back the new error onto 'errors'; if given a NULL pointer,
// it reports the error via LOG(ERROR).
//
// You can also do conditional logging:
//
//   LOG_IF(INFO, num_cookies > 10) << "Got lots of cookies";
//
// You can also do occasional logging (log every n'th occurrence of an
// event):
//
//   LOG_EVERY_N(INFO, 10) << "Got the " << google::COUNTER << "th cookie";
//
// The above will cause log messages to be output on the 1st, 11th, 21st, ...
// times it is executed.  Note that the special google::COUNTER value is used
// to identify which repetition is happening.
//
// You can also do occasional conditional logging (log every n'th
// occurrence of an event, when condition is satisfied):
//
//   LOG_IF_EVERY_N(INFO, (size > 1024), 10) << "Got the " << google::COUNTER
//                                           << "th big cookie";
//
// You can log messages the first N times your code executes a line. E.g.
//
//   LOG_FIRST_N(INFO, 20) << "Got the " << google::COUNTER << "th cookie";
//
// Outputs log messages for the first 20 times it is executed.
//
// Analogous SYSLOG, SYSLOG_IF, and SYSLOG_EVERY_N macros are available.
// These log to syslog as well as to the normal logs.  If you use these at
// all, you need to be aware that syslog can drastically reduce performance,
// especially if it is configured for remote logging!  Don't use these
// unless you fully understand this and have a concrete need to use them.
// Even then, try to minimize your use of them.
//
// 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";
//
//   DLOG_EVERY_N(INFO, 10) << "Got the " << google::COUNTER << "th cookie";
//
// All "debug mode" logging is compiled away to nothing for non-debug mode
// compiles.
//
// 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=mapreduce=2,file=1,gfs*=3 --v=0
// will cause:
//   a. VLOG(2) and lower messages to be printed from mapreduce.{h,cc}
//   b. VLOG(1) and lower messages to be printed from file.{h,cc}
//   c. VLOG(3) and lower messages to be printed from files prefixed with "gfs"
//   d. 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.
//
// 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_EVERY_N "verbose level"
// condition macros for sample cases, when some extra computation and
// preparation for logs is not needed.
//   VLOG_EVERY_N(1, 10)
//      << "I'm printed every 10th occurrence, and when you run the program "
//         "with --v=1 or more. Present occurrence is " << google::COUNTER;
//
// The supported severity levels for macros that allow you to specify one
// are (in increasing order of severity) INFO, WARNING, ERROR, and FATAL.
// Note that messages of a given severity are logged not only in the
// logfile for that severity, but also in all logfiles of lower severity.
// E.g., a message of severity FATAL will be logged to the logfiles of
// severity FATAL, ERROR, WARNING, and INFO.
//
// There is also the special severity of DFATAL, which logs FATAL in
// debug mode, ERROR in normal mode.
//
// Very important: logging a message at the FATAL severity level causes
// the program to terminate (after the message is logged).
//
// Unless otherwise specified, logs will be written to the filename
// "<program name>.<hostname>.<user name>.log.<severity level>.", followed
// by the date, time, and pid (you can't prevent the date, time, and pid
// from being in the filename).
//
// The logging code takes two flags:
//     --v=#           set the verbose level
//     --logtostderr   log all the messages to stderr instead of to logfiles

// LOG LINE PREFIX FORMAT
//
// Log lines have this form:
//
//     Lmmdd hh:mm:ss.uuuuuu threadid file:line] msg...
//
// where the fields are defined as follows:
//
//   L                A single character, representing the log level
//                    (eg 'I' for INFO)
//   mm               The month (zero padded; ie May is '05')
//   dd               The day (zero padded)
//   hh:mm:ss.uuuuuu  Time in hours, minutes and fractional seconds
//   threadid         The space-padded thread ID as returned by GetTID()
//                    (this matches the PID on Linux)
//   file             The file name
//   line             The line number
//   msg              The user-supplied message
//
// Example:
//
//   I1103 11:57:31.739339 24395 google.cc:2341] Command line: ./some_prog
//   I1103 11:57:31.739403 24395 google.cc:2342] Process id 24395
//
// NOTE: although the microseconds are useful for comparing events on
// a single machine, clocks on different machines may not be well
// synchronized.  Hence, use caution when comparing the low bits of
// timestamps from different machines.

// Set whether log messages go to stderr instead of logfiles
ABSL_DECLARE_FLAG(bool, logtostderr);

// Set whether log messages go to stderr in addition to logfiles.
ABSL_DECLARE_FLAG(bool, alsologtostderr);

// Set color messages logged to stderr (if supported by terminal).
ABSL_DECLARE_FLAG(bool, colorlogtostderr);

// Log messages at a level >= this flag are automatically sent to
// stderr in addition to log files.
ABSL_DECLARE_FLAG(int, stderrthreshold);

// Set whether the log prefix should be prepended to each line of output.
ABSL_DECLARE_FLAG(bool, log_prefix);

// Log messages at a level <= this flag are buffered.
// Log messages at a higher level are flushed immediately.
ABSL_DECLARE_FLAG(int, logbuflevel);

// Sets the maximum number of seconds which logs may be buffered for.
ABSL_DECLARE_FLAG(int, logbufsecs);

// Log suppression level: messages logged at a lower level than this
// are suppressed.
ABSL_DECLARE_FLAG(int, minloglevel);

// If specified, logfiles are written into this directory instead of the
// default logging directory.
ABSL_DECLARE_FLAG(std::string, log_dir);

// Set the log file mode.
ABSL_DECLARE_FLAG(int, logfile_mode);

// Sets the path of the directory into which to put additional links
// to the log files.
ABSL_DECLARE_FLAG(std::string, log_link);

ABSL_DECLARE_FLAG(int, v);  // in vlog_is_on.cc

// Sets the maximum log file size (in MB).
ABSL_DECLARE_FLAG(int, max_log_size);

// Sets whether to avoid logging to the disk if the disk is full.
ABSL_DECLARE_FLAG(bool, stop_logging_if_full_disk);

// Log messages below the GOOGLE_STRIP_LOG level will be compiled away for
// security reasons. See LOG(severtiy) below.

// A few definitions of macros that don't generate much code.  Since
// LOG(INFO) and its ilk are used all over our code, it's
// better to have compact code for these operations.

#if GOOGLE_STRIP_LOG == 0
#define COMPACT_GOOGLE_LOG_INFO google::LogMessage(__FILE__, __LINE__)
#define LOG_TO_STRING_INFO(message) \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_INFO, message)
#else
#define COMPACT_GOOGLE_LOG_INFO google::NullStream()
#define LOG_TO_STRING_INFO(message) google::NullStream()
#endif

#if GOOGLE_STRIP_LOG <= 1
#define COMPACT_GOOGLE_LOG_WARNING \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_WARNING)
#define LOG_TO_STRING_WARNING(message) \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_WARNING, message)
#else
#define COMPACT_GOOGLE_LOG_WARNING google::NullStream()
#define LOG_TO_STRING_WARNING(message) google::NullStream()
#endif

#if GOOGLE_STRIP_LOG <= 2
#define COMPACT_GOOGLE_LOG_ERROR \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_ERROR)
#define LOG_TO_STRING_ERROR(message) \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_ERROR, message)
#else
#define COMPACT_GOOGLE_LOG_ERROR google::NullStream()
#define LOG_TO_STRING_ERROR(message) google::NullStream()
#endif

#if GOOGLE_STRIP_LOG <= 3
#define COMPACT_GOOGLE_LOG_FATAL google::LogMessageFatal(__FILE__, __LINE__)
#define LOG_TO_STRING_FATAL(message) \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_FATAL, message)
#else
#define COMPACT_GOOGLE_LOG_FATAL google::NullStreamFatal()
#define LOG_TO_STRING_FATAL(message) google::NullStreamFatal()
#endif

#if defined(NDEBUG) && !defined(DCHECK_ALWAYS_ON)
#define DCHECK_IS_ON() 0
#else
#define DCHECK_IS_ON() 1
#endif

// For DFATAL, we want to use LogMessage (as opposed to
// LogMessageFatal), to be consistent with the original behavior.
#if !DCHECK_IS_ON()
#define COMPACT_GOOGLE_LOG_DFATAL COMPACT_GOOGLE_LOG_ERROR
#elif GOOGLE_STRIP_LOG <= 3
#define COMPACT_GOOGLE_LOG_DFATAL \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_FATAL)
#else
#define COMPACT_GOOGLE_LOG_DFATAL google::NullStreamFatal()
#endif

#define GOOGLE_LOG_INFO(counter)                                     \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_INFO, counter, \
                     &google::LogMessage::SendToLog)
#define SYSLOG_INFO(counter)                                         \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_INFO, counter, \
                     &google::LogMessage::SendToSyslogAndLog)
#define GOOGLE_LOG_WARNING(counter)                                     \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_WARNING, counter, \
                     &google::LogMessage::SendToLog)
#define SYSLOG_WARNING(counter)                                         \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_WARNING, counter, \
                     &google::LogMessage::SendToSyslogAndLog)
#define GOOGLE_LOG_ERROR(counter)                                     \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_ERROR, counter, \
                     &google::LogMessage::SendToLog)
#define SYSLOG_ERROR(counter)                                         \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_ERROR, counter, \
                     &google::LogMessage::SendToSyslogAndLog)
#define GOOGLE_LOG_FATAL(counter)                                     \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_FATAL, counter, \
                     &google::LogMessage::SendToLog)
#define SYSLOG_FATAL(counter)                                         \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_FATAL, counter, \
                     &google::LogMessage::SendToSyslogAndLog)
#define GOOGLE_LOG_DFATAL(counter)                                      \
  google::LogMessage(__FILE__, __LINE__, google::DFATAL_LEVEL, counter, \
                     &google::LogMessage::SendToLog)
#define SYSLOG_DFATAL(counter)                                          \
  google::LogMessage(__FILE__, __LINE__, google::DFATAL_LEVEL, counter, \
                     &google::LogMessage::SendToSyslogAndLog)

#if defined(WIN32) || defined(_WIN32) || defined(__WIN32__) || \
    defined(__CYGWIN__) || defined(__CYGWIN32__)
// A very useful logging macro to log windows errors:
#define LOG_SYSRESULT(result)                                           \
  if (FAILED(HRESULT_FROM_WIN32(result))) {                             \
    LPSTR message = NULL;                                               \
    LPSTR msg = reinterpret_cast<LPSTR>(&message);                      \
    DWORD message_length = FormatMessageA(                              \
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, 0, \
        result, 0, msg, 100, NULL);                                     \
    if (message_length > 0) {                                           \
      google::LogMessage(__FILE__, __LINE__, google::GLOG_ERROR, 0,     \
                         &google::LogMessage::SendToLog)                \
              .stream()                                                 \
          << reinterpret_cast<const char*>(message);                    \
      LocalFree(message);                                               \
    }                                                                   \
  }
#endif

// We use the preprocessor's merging operator, "##", so that, e.g.,
// LOG(INFO) becomes the token 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(severity) COMPACT_GOOGLE_LOG_##severity.stream()
#define SYSLOG(severity) SYSLOG_##severity(0).stream()

namespace google {

// Initialize google's logging library. You will see the program name
// specified by argv0 in log outputs.
GOOGLE_GLOG_DLL_DECL void InitGoogleLogging(const char* argv0);

// Shutdown google's logging library.
GOOGLE_GLOG_DLL_DECL void ShutdownGoogleLogging();

// Install a function which will be called after LOG(FATAL).
GOOGLE_GLOG_DLL_DECL void InstallFailureFunction(void (*fail_func)());

class LogSink;  // defined below

// If a non-NULL sink pointer is given, we push this message to that sink.
// For LOG_TO_SINK we then do normal LOG(severity) logging as well.
// This is useful for capturing messages and passing/storing them
// somewhere more specific than the global log of the process.
// Argument types:
//   LogSink* sink;
//   LogSeverity severity;
// The cast is to disambiguate NULL arguments.
#define LOG_TO_SINK(sink, severity)                               \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                     static_cast<google::LogSink*>(sink), true)   \
      .stream()
#define LOG_TO_SINK_BUT_NOT_TO_LOGFILE(sink, severity)            \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                     static_cast<google::LogSink*>(sink), false)  \
      .stream()

// If a non-NULL string pointer is given, we write this message to that string.
// We then do normal LOG(severity) logging as well.
// This is useful for capturing messages and storing them somewhere more
// specific than the global log of the process.
// Argument types:
//   string* message;
//   LogSeverity severity;
// The cast is to disambiguate NULL arguments.
// NOTE: LOG(severity) expands to LogMessage().stream() for the specified
// severity.
#define LOG_TO_STRING(severity, message) \
  LOG_TO_STRING_##severity(static_cast<string*>(message)).stream()

// If a non-NULL pointer is given, we push the message onto the end
// of a vector of strings; otherwise, we report it with LOG(severity).
// This is handy for capturing messages and perhaps passing them back
// to the caller, rather than reporting them immediately.
// Argument types:
//   LogSeverity severity;
//   vector<string> *outvec;
// The cast is to disambiguate NULL arguments.
#define LOG_STRING(severity, outvec)                                       \
  LOG_TO_STRING_##severity(static_cast<std::vector<std::string>*>(outvec)) \
      .stream()

#define LOG_IF(severity, condition) \
  static_cast<void>(0),             \
      !(condition) ? (void)0 : google::LogMessageVoidify() & LOG(severity)
#define SYSLOG_IF(severity, condition) \
  static_cast<void>(0),                \
      !(condition) ? (void)0 : google::LogMessageVoidify() & SYSLOG(severity)

#define LOG_ASSERT(condition) \
  LOG_IF(FATAL, !(condition)) << "Assert failed: " #condition
#define SYSLOG_ASSERT(condition) \
  SYSLOG_IF(FATAL, !(condition)) << "Assert failed: " #condition

// CHECK dies with a fatal error if condition is not true.  It is *not*
// controlled by DCHECK_IS_ON(), so the check will be executed regardless of
// compilation mode.  Therefore, it is safe to do things like:
//    CHECK(fp->Write(x) == 4)
#define CHECK(condition)                                       \
  LOG_IF(FATAL, GOOGLE_PREDICT_BRANCH_NOT_TAKEN(!(condition))) \
      << "Check failed: " #condition " "

// A container for a string pointer which can be evaluated to a bool -
// true iff the pointer is NULL.
struct CheckOpString {
  CheckOpString(std::string* str) : str_(str) {}
  // No destructor: if str_ is non-NULL, we're about to LOG(FATAL),
  // so there's no point in cleaning up str_.
  operator bool() const {
    return GOOGLE_PREDICT_BRANCH_NOT_TAKEN(str_ != NULL);
  }
  std::string* str_;
};

// Function is overloaded for integral types to allow static const
// integrals declared in classes and not defined to be used as arguments to
// CHECK* macros. It's not encouraged though.
template <class T>
inline const T& GetReferenceableValue(const T& t) {
  return t;
}
inline char GetReferenceableValue(char t) { return t; }
inline unsigned char GetReferenceableValue(unsigned char t) { return t; }
inline signed char GetReferenceableValue(signed char t) { return t; }
inline int16_t GetReferenceableValue(int16_t t) { return t; }
inline uint16_t GetReferenceableValue(uint16_t t) { return t; }
inline int GetReferenceableValue(int t) { return t; }
inline unsigned int GetReferenceableValue(unsigned int t) { return t; }
inline int64_t GetReferenceableValue(int64_t t) { return t; }
inline uint64_t GetReferenceableValue(uint64_t t) { return t; }

// This is a dummy class to define the following operator.
struct DummyClassToDefineOperator {};
}  // namespace google

// Define global operator<< to declare using ::operator<<.
// This declaration will allow use to use CHECK macros for user
// defined classes which have operator<< (e.g., stl_logging.h).
inline std::ostream& operator<<(std::ostream& out,
                                const google::DummyClassToDefineOperator&) {
  return out;
}

namespace google {

// This formats a value for a failing CHECK_XX statement.  Ordinarily,
// it uses the definition for operator<<, with a few special cases below.
template <typename T>
inline void MakeCheckOpValueString(std::ostream* os, const T& v) {
  (*os) << v;
}

// Overrides for char types provide readable values for unprintable
// characters.
template <>
GOOGLE_GLOG_DLL_DECL void MakeCheckOpValueString(std::ostream* os,
                                                 const char& v);
template <>
GOOGLE_GLOG_DLL_DECL void MakeCheckOpValueString(std::ostream* os,
                                                 const signed char& v);
template <>
GOOGLE_GLOG_DLL_DECL void MakeCheckOpValueString(std::ostream* os,
                                                 const unsigned char& v);

// Build the error message string. Specify no inlining for code size.
template <typename T1, typename T2>
std::string* MakeCheckOpString(const T1& v1, const T2& v2,
                               const char* exprtext) ATTRIBUTE_NOINLINE;

// Provide printable value for nullptr_t
template <>
GOOGLE_GLOG_DLL_DECL void MakeCheckOpValueString(std::ostream* os,
                                                 const std::nullptr_t& v);

namespace base {
namespace internal {

// If "s" is less than base_logging::INFO, returns base_logging::INFO.
// If "s" is greater than base_logging::FATAL, returns
// base_logging::ERROR.  Otherwise, returns "s".
LogSeverity NormalizeSeverity(LogSeverity s);

}  // namespace internal

// A helper class for formatting "expr (V1 vs. V2)" in a CHECK_XX
// statement.  See MakeCheckOpString for sample usage.  Other
// approaches were considered: use of a template method (e.g.,
// base::BuildCheckOpString(exprtext, base::Print<T1>, &v1,
// base::Print<T2>, &v2), however this approach has complications
// related to volatile arguments and function-pointer arguments).
class GOOGLE_GLOG_DLL_DECL CheckOpMessageBuilder {
 public:
  // Inserts "exprtext" and " (" to the stream.
  explicit CheckOpMessageBuilder(const char* exprtext);
  // Deletes "stream_".
  ~CheckOpMessageBuilder();
  // For inserting the first variable.
  std::ostream* ForVar1() { return stream_; }
  // For inserting the second variable (adds an intermediate " vs. ").
  std::ostream* ForVar2();
  // Get the result (inserts the closing ")").
  std::string* NewString();

 private:
  std::ostringstream* stream_;
};

}  // namespace base

template <typename T1, typename T2>
std::string* MakeCheckOpString(const T1& v1, const T2& v2,
                               const char* exprtext) {
  base::CheckOpMessageBuilder comb(exprtext);
  MakeCheckOpValueString(comb.ForVar1(), v1);
  MakeCheckOpValueString(comb.ForVar2(), v2);
  return comb.NewString();
}

// 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 <typename T1, typename T2>                                    \
  inline std::string* name##Impl(const T1& v1, const T2& v2,             \
                                 const char* exprtext) {                 \
    if (GOOGLE_PREDICT_TRUE(v1 op v2))                                   \
      return NULL;                                                       \
    else                                                                 \
      return MakeCheckOpString(v1, v2, exprtext);                        \
  }                                                                      \
  inline std::string* name##Impl(int v1, int v2, const char* exprtext) { \
    return name##Impl<int, int>(v1, v2, exprtext);                       \
  }

// We use the full name Check_EQ, Check_NE, etc. in case the file including
// base/logging.h provides its own #defines for the simpler names EQ, NE, etc.
// This happens if, for example, those are used as token names in a
// yacc grammar.
DEFINE_CHECK_OP_IMPL(Check_EQ, ==)  // Compilation error with CHECK_EQ(NULL, x)?
DEFINE_CHECK_OP_IMPL(Check_NE, !=)  // Use CHECK(x == NULL) instead.
DEFINE_CHECK_OP_IMPL(Check_LE, <=)
DEFINE_CHECK_OP_IMPL(Check_LT, <)
DEFINE_CHECK_OP_IMPL(Check_GE, >=)
DEFINE_CHECK_OP_IMPL(Check_GT, >)
#undef DEFINE_CHECK_OP_IMPL

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

#if defined(STATIC_ANALYSIS)
// Only for static analysis tool to know that it is equivalent to assert
#define CHECK_OP_LOG(name, op, val1, val2, log) CHECK((val1)op(val2))
#elif DCHECK_IS_ON()
// In debug mode, avoid constructing CheckOpStrings if possible,
// to reduce the overhead of CHECK statments by 2x.
// Real DCHECK-heavy tests have seen 1.5x speedups.

// The meaning of "string" might be different between now and
// when this macro gets invoked (e.g., if someone is experimenting
// with other string implementations that get defined after this
// file is included).  Save the current meaning now and use it
// in the macro.
typedef std::string _Check_string;
#define CHECK_OP_LOG(name, op, val1, val2, log)                             \
  while (google::_Check_string* _result = google::Check##name##Impl(        \
             google::GetReferenceableValue(val1),                           \
             google::GetReferenceableValue(val2), #val1 " " #op " " #val2)) \
  log(__FILE__, __LINE__, google::CheckOpString(_result)).stream()
#else
// In optimized mode, use CheckOpString to hint to compiler that
// the while condition is unlikely.
#define CHECK_OP_LOG(name, op, val1, val2, log)                             \
  while (google::CheckOpString _result = google::Check##name##Impl(         \
             google::GetReferenceableValue(val1),                           \
             google::GetReferenceableValue(val2), #val1 " " #op " " #val2)) \
  log(__FILE__, __LINE__, _result).stream()
#endif  // STATIC_ANALYSIS, DCHECK_IS_ON()

#if GOOGLE_STRIP_LOG <= 3
#define CHECK_OP(name, op, val1, val2) \
  CHECK_OP_LOG(name, op, val1, val2, google::LogMessageFatal)
#else
#define CHECK_OP(name, op, val1, val2) \
  CHECK_OP_LOG(name, op, val1, val2, google::NullStreamFatal)
#endif  // STRIP_LOG <= 3

// Equality/Inequality checks - compare two values, and log a FATAL 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:
//   CHECK_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:
//   CHECK_EQ(string("abc")[1], 'b');
//
// WARNING: These don't 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 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)

// Check that the input is non NULL.  This very useful in constructor
// initializer lists.

#define CHECK_NOTNULL(val) \
  google::CheckNotNull(__FILE__, __LINE__, "'" #val "' Must be non NULL", (val))

// Helper functions for string comparisons.
// To avoid bloat, the definitions are in logging.cc.
#define DECLARE_CHECK_STROP_IMPL(func, expected)                 \
  GOOGLE_GLOG_DLL_DECL std::string* Check##func##expected##Impl( \
      const char* s1, const char* s2, const char* names);
DECLARE_CHECK_STROP_IMPL(strcmp, true)
DECLARE_CHECK_STROP_IMPL(strcmp, false)
DECLARE_CHECK_STROP_IMPL(strcasecmp, true)
DECLARE_CHECK_STROP_IMPL(strcasecmp, false)
#undef DECLARE_CHECK_STROP_IMPL

// Helper macro for string comparisons.
// Don't use this macro directly in your code, use CHECK_STREQ et al below.
#define CHECK_STROP(func, op, expected, s1, s2)                               \
  while (google::CheckOpString _result = google::Check##func##expected##Impl( \
             (s1), (s2), #s1 " " #op " " #s2))                                \
  LOG(FATAL) << *_result.str_

// String (char*) equality/inequality checks.
// CASE versions are case-insensitive.
//
// Note that "s1" and "s2" may be temporary strings which are destroyed
// by the compiler at the end of the current "full expression"
// (e.g. CHECK_STREQ(Foo().c_str(), Bar().c_str())).

#define CHECK_STREQ(s1, s2) CHECK_STROP(strcmp, ==, true, s1, s2)
#define CHECK_STRNE(s1, s2) CHECK_STROP(strcmp, !=, false, s1, s2)
#define CHECK_STRCASEEQ(s1, s2) CHECK_STROP(strcasecmp, ==, true, s1, s2)
#define CHECK_STRCASENE(s1, s2) CHECK_STROP(strcasecmp, !=, false, s1, s2)

#define CHECK_INDEX(I, A) CHECK(I < (sizeof(A) / sizeof(A[0])))
#define CHECK_BOUND(B, A) CHECK(B <= (sizeof(A) / sizeof(A[0])))

#define CHECK_DOUBLE_EQ(val1, val2)                \
  do {                                             \
    CHECK_LE((val1), (val2) + 0.000000000000001L); \
    CHECK_GE((val1), (val2)-0.000000000000001L);   \
  } while (0)

#define CHECK_NEAR(val1, val2, margin)   \
  do {                                   \
    CHECK_LE((val1), (val2) + (margin)); \
    CHECK_GE((val1), (val2) - (margin)); \
  } while (0)

// perror()..googly style!
//
// PLOG() and PLOG_IF() and PCHECK() behave exactly like their LOG* and
// CHECK equivalents with the addition that they postpend a description
// of the current state of errno to their output lines.

#define PLOG(severity) GOOGLE_PLOG(severity, 0).stream()

#define GOOGLE_PLOG(severity, counter)                                 \
  google::ErrnoLogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                          counter, &google::LogMessage::SendToLog)

#define PLOG_IF(severity, condition) \
  static_cast<void>(0),              \
      !(condition) ? (void)0 : google::LogMessageVoidify() & PLOG(severity)

// A CHECK() macro that postpends errno if the condition is false. E.g.
//
// if (poll(fds, nfds, timeout) == -1) { PCHECK(errno == EINTR); ... }
#define PCHECK(condition)                                       \
  PLOG_IF(FATAL, GOOGLE_PREDICT_BRANCH_NOT_TAKEN(!(condition))) \
      << "Check failed: " #condition " "

// A CHECK() macro that lets you assert the success of a function that
// returns -1 and sets errno in case of an error. E.g.
//
// CHECK_ERR(mkdir(path, 0700));
//
// or
//
// int fd = open(filename, flags); CHECK_ERR(fd) << ": open " << filename;
#define CHECK_ERR(invocation)                                         \
  PLOG_IF(FATAL, GOOGLE_PREDICT_BRANCH_NOT_TAKEN((invocation) == -1)) \
      << #invocation

// Use macro expansion to create, for each use of LOG_EVERY_N(), static
// variables with the __LINE__ expansion as part of the variable name.
#define LOG_EVERY_N_VARNAME(base, line) LOG_EVERY_N_VARNAME_CONCAT(base, line)
#define LOG_EVERY_N_VARNAME_CONCAT(base, line) base##line

#define LOG_OCCURRENCES LOG_EVERY_N_VARNAME(occurrences_, __LINE__)
#define LOG_OCCURRENCES_MOD_N LOG_EVERY_N_VARNAME(occurrences_mod_n_, __LINE__)

#define SOME_KIND_OF_LOG_EVERY_N(severity, n, what_to_do)         \
  static int LOG_OCCURRENCES = 0, LOG_OCCURRENCES_MOD_N = 0;      \
  ++LOG_OCCURRENCES;                                              \
  if (++LOG_OCCURRENCES_MOD_N > n) LOG_OCCURRENCES_MOD_N -= n;    \
  if (LOG_OCCURRENCES_MOD_N == 1)                                 \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                     LOG_OCCURRENCES, &what_to_do)                \
      .stream()

#define SOME_KIND_OF_LOG_IF_EVERY_N(severity, condition, n, what_to_do)       \
  static int LOG_OCCURRENCES = 0, LOG_OCCURRENCES_MOD_N = 0;                  \
  ++LOG_OCCURRENCES;                                                          \
  if (condition &&                                                            \
      ((LOG_OCCURRENCES_MOD_N = (LOG_OCCURRENCES_MOD_N + 1) % n) == (1 % n))) \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_##severity,             \
                     LOG_OCCURRENCES, &what_to_do)                            \
      .stream()

#define SOME_KIND_OF_PLOG_EVERY_N(severity, n, what_to_do)             \
  static int LOG_OCCURRENCES = 0, LOG_OCCURRENCES_MOD_N = 0;           \
  ++LOG_OCCURRENCES;                                                   \
  if (++LOG_OCCURRENCES_MOD_N > n) LOG_OCCURRENCES_MOD_N -= n;         \
  if (LOG_OCCURRENCES_MOD_N == 1)                                      \
  google::ErrnoLogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                          LOG_OCCURRENCES, &what_to_do)                \
      .stream()

#define SOME_KIND_OF_LOG_FIRST_N(severity, n, what_to_do)         \
  static int LOG_OCCURRENCES = 0;                                 \
  if (LOG_OCCURRENCES <= n) ++LOG_OCCURRENCES;                    \
  if (LOG_OCCURRENCES <= n)                                       \
  google::LogMessage(__FILE__, __LINE__, google::GLOG_##severity, \
                     LOG_OCCURRENCES, &what_to_do)                \
      .stream()

namespace logging_internal {
template <bool>
struct CompileAssert {};
struct CrashReason;
}  // namespace logging_internal

#define LOG_EVERY_N(severity, n) \
  SOME_KIND_OF_LOG_EVERY_N(severity, (n), google::LogMessage::SendToLog)

#define SYSLOG_EVERY_N(severity, n)       \
  SOME_KIND_OF_LOG_EVERY_N(severity, (n), \
                           google::LogMessage::SendToSyslogAndLog)

#define PLOG_EVERY_N(severity, n) \
  SOME_KIND_OF_PLOG_EVERY_N(severity, (n), google::LogMessage::SendToLog)

#define LOG_FIRST_N(severity, n) \
  SOME_KIND_OF_LOG_FIRST_N(severity, (n), google::LogMessage::SendToLog)

#define LOG_IF_EVERY_N(severity, condition, n)            \
  SOME_KIND_OF_LOG_IF_EVERY_N(severity, (condition), (n), \
                              google::LogMessage::SendToLog)

// We want the special COUNTER value available for LOG_EVERY_X()'ed messages
enum PRIVATE_Counter { COUNTER };

#ifdef _MSC_VER
// 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.
#define COMPACT_GOOGLE_LOG_0 COMPACT_GOOGLE_LOG_ERROR
#define SYSLOG_0 SYSLOG_ERROR
#define LOG_TO_STRING_0 LOG_TO_STRING_ERROR
// Needed for LOG_IS_ON(ERROR).
const LogSeverity GLOG_0 = GLOG_ERROR;
#endif

// Plus some debug-logging macros that get compiled to nothing for production

#if DCHECK_IS_ON()

#define DLOG(severity) LOG(severity)
#define DVLOG(verboselevel) VLOG(verboselevel)
#define DLOG_IF(severity, condition) LOG_IF(severity, condition)
#define DLOG_EVERY_N(severity, n) LOG_EVERY_N(severity, n)
#define DLOG_IF_EVERY_N(severity, condition, n) \
  LOG_IF_EVERY_N(severity, condition, n)
#define DLOG_ASSERT(condition) LOG_ASSERT(condition)

// debug-only checking.  executed if DCHECK_IS_ON().
#define DCHECK(condition) CHECK(condition)
#define DCHECK_EQ(val1, val2) CHECK_EQ(val1, val2)
#define DCHECK_NE(val1, val2) CHECK_NE(val1, val2)
#define DCHECK_LE(val1, val2) CHECK_LE(val1, val2)
#define DCHECK_LT(val1, val2) CHECK_LT(val1, val2)
#define DCHECK_GE(val1, val2) CHECK_GE(val1, val2)
#define DCHECK_GT(val1, val2) CHECK_GT(val1, val2)
#define DCHECK_NOTNULL(val) CHECK_NOTNULL(val)
#define DCHECK_STREQ(str1, str2) CHECK_STREQ(str1, str2)
#define DCHECK_STRCASEEQ(str1, str2) CHECK_STRCASEEQ(str1, str2)
#define DCHECK_STRNE(str1, str2) CHECK_STRNE(str1, str2)
#define DCHECK_STRCASENE(str1, str2) CHECK_STRCASENE(str1, str2)

#else  // !DCHECK_IS_ON()

#define DLOG(severity)  \
  static_cast<void>(0), \
      true ? (void)0 : google::LogMessageVoidify() & LOG(severity)

#define DVLOG(verboselevel)                                 \
  static_cast<void>(0), (true || !VLOG_IS_ON(verboselevel)) \
                            ? (void)0                       \
                            : google::LogMessageVoidify() & LOG(INFO)

#define DLOG_IF(severity, condition)           \
  static_cast<void>(0), (true || !(condition)) \
                            ? (void)0          \
                            : google::LogMessageVoidify() & LOG(severity)

#define DLOG_EVERY_N(severity, n) \
  static_cast<void>(0),           \
      true ? (void)0 : google::LogMessageVoidify() & LOG(severity)

#define DLOG_IF_EVERY_N(severity, condition, n) \
  static_cast<void>(0), (true || !(condition))  \
                            ? (void)0           \
                            : google::LogMessageVoidify() & LOG(severity)

#define DLOG_ASSERT(condition) \
  static_cast<void>(0), true ? (void)0 : LOG_ASSERT(condition)

// MSVC warning C4127: conditional expression is constant
#define DCHECK(condition)              \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK(condition)

#define DCHECK_EQ(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_EQ(val1, val2)

#define DCHECK_NE(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_NE(val1, val2)

#define DCHECK_LE(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_LE(val1, val2)

#define DCHECK_LT(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_LT(val1, val2)

#define DCHECK_GE(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_GE(val1, val2)

#define DCHECK_GT(val1, val2)          \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_GT(val1, val2)

// You may see warnings in release mode if you don't use the return
// value of DCHECK_NOTNULL. Please just use DCHECK for such cases.
#define DCHECK_NOTNULL(val) (val)

#define DCHECK_STREQ(str1, str2)       \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_STREQ(str1, str2)

#define DCHECK_STRCASEEQ(str1, str2)   \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_STRCASEEQ(str1, str2)

#define DCHECK_STRNE(str1, str2)       \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_STRNE(str1, str2)

#define DCHECK_STRCASENE(str1, str2)   \
  GLOG_MSVC_PUSH_DISABLE_WARNING(4127) \
  while (false) GLOG_MSVC_POP_WARNING() CHECK_STRCASENE(str1, str2)

#endif  // DCHECK_IS_ON()

// Log only in verbose mode.

#define VLOG(verboselevel) LOG_IF(INFO, VLOG_IS_ON(verboselevel))

#define VLOG_EVERY_N(verboselevel, n) \
  LOG_IF_EVERY_N(INFO, VLOG_IS_ON(verboselevel), n)

namespace base_logging {

// LogMessage::LogStream is a std::ostream backed by this streambuf.
// This class ignores overflow and leaves two bytes at the end of the
// buffer to allow for a '\n' and '\0'.
class GOOGLE_GLOG_DLL_DECL LogStreamBuf : public std::streambuf {
 public:
  // REQUIREMENTS: "len" must be >= 2 to account for the '\n' and '\0'.
  LogStreamBuf(char* buf, int len) { setp(buf, buf + len - 2); }

  // This effectively ignores overflow.
  virtual int_type overflow(int_type ch) { return ch; }

  // Legacy public ostrstream method.
  size_t pcount() const { return pptr() - pbase(); }
  char* pbase() const { return std::streambuf::pbase(); }
};

}  // namespace base_logging

//
// 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 GOOGLE_GLOG_DLL_DECL LogMessage {
 public:
  enum {
    // Passing kNoLogPrefix for the line number disables the
    // log-message prefix. Useful for using the LogMessage
    // infrastructure as a printing utility. See also the --log_prefix
    // flag for controlling the log-message prefix on an
    // application-wide basis.
    kNoLogPrefix = -1
  };

  // LogStream inherit from non-DLL-exported class (std::ostrstream)
  // and VC++ produces a warning for this situation.
  // However, MSDN says "C4275 can be ignored in Microsoft Visual C++
  // 2005 if you are deriving from a type in the Standard C++ Library"
  // http://msdn.microsoft.com/en-us/library/3tdb471s(VS.80).aspx
  // Let's just ignore the warning.
  GLOG_MSVC_PUSH_DISABLE_WARNING(4275)
  class GOOGLE_GLOG_DLL_DECL LogStream : public std::ostream {
    GLOG_MSVC_POP_WARNING()
   public:
    LogStream(char* buf, int len, int ctr)
        : std::ostream(NULL), streambuf_(buf, len), ctr_(ctr), self_(this) {
      rdbuf(&streambuf_);
    }

    int ctr() const { return ctr_; }
    void set_ctr(int ctr) { ctr_ = ctr; }
    LogStream* self() const { return self_; }

    // Legacy std::streambuf methods.
    size_t pcount() const { return streambuf_.pcount(); }
    char* pbase() const { return streambuf_.pbase(); }
    char* str() const { return pbase(); }

   private:
    LogStream(const LogStream&);
    LogStream& operator=(const LogStream&);
    base_logging::LogStreamBuf streambuf_;
    int ctr_;          // Counter hack (for the LOG_EVERY_X() macro)
    LogStream* self_;  // Consistency check hack
  };

 public:
  // icc 8 requires this typedef to avoid an internal compiler error.
  typedef void (LogMessage::*SendMethod)();

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

  // Two special constructors that generate reduced amounts of code at
  // LOG call sites for common cases.

  // Used for LOG(INFO): Implied are:
  // severity = INFO, ctr = 0, send_method = &LogMessage::SendToLog.
  //
  // Using this constructor instead of the more complex constructor above
  // saves 19 bytes per call site.
  LogMessage(const char* file, int line);

  // Used for LOG(severity) where severity != INFO.  Implied
  // are: ctr = 0, send_method = &LogMessage::SendToLog
  //
  // Using this constructor instead of the more complex constructor above
  // saves 17 bytes per call site.
  LogMessage(const char* file, int line, LogSeverity severity);

  // Constructor to log this message to a specified sink (if not NULL).
  // Implied are: ctr = 0, send_method = &LogMessage::SendToSinkAndLog if
  // also_send_to_log is true, send_method = &LogMessage::SendToSink otherwise.
  LogMessage(const char* file, int line, LogSeverity severity, LogSink* sink,
             bool also_send_to_log);

  // Constructor where we also give a vector<string> pointer
  // for storing the messages (if the pointer is not NULL).
  // Implied are: ctr = 0, send_method = &LogMessage::SaveOrSendToLog.
  LogMessage(const char* file, int line, LogSeverity severity,
             std::vector<std::string>* outvec);

  // Constructor where we also give a string pointer for storing the
  // message (if the pointer is not NULL).  Implied are: ctr = 0,
  // send_method = &LogMessage::WriteToStringAndLog.
  LogMessage(const char* file, int line, LogSeverity severity,
             std::string* message);

  // A special constructor used for check failures
  LogMessage(const char* file, int line, const CheckOpString& result);

  ~LogMessage();

  // Flush a buffered message to the sink set in the constructor.  Always
  // called by the destructor, it may also be called from elsewhere if
  // needed.  Only the first call is actioned; any later ones are ignored.
  void Flush();

  // An arbitrary limit on the length of a single log message.  This
  // is so that streaming can be done more efficiently.
  static const size_t kMaxLogMessageLen;

  // Theses should not be called directly outside of logging.*,
  // only passed as SendMethod arguments to other LogMessage methods:
  void SendToLog();           // Actually dispatch to the logs
  void SendToSyslogAndLog();  // Actually dispatch to syslog and the logs

  // Call abort() or similar to perform LOG(FATAL) crash.
  static void ATTRIBUTE_NORETURN Fail();

  std::ostream& stream();

  int preserved_errno() const;

  // Must be called without the log_mutex held.  (L < log_mutex)
  static int64_t num_messages(int severity);

  struct LogMessageData;

 private:
  // Fully internal SendMethod cases:
  void SendToSinkAndLog();  // Send to sink if provided and dispatch to the logs
  void SendToSink();        // Send to sink if provided, do nothing otherwise.

  // Write to string if provided and dispatch to the logs.
  void WriteToStringAndLog();

  void SaveOrSendToLog();  // Save to stringvec if provided, else to logs

  void Init(const char* file, int line, LogSeverity severity,
            void (LogMessage::*send_method)());

  // Used to fill in crash information during LOG(FATAL) failures.
  void RecordCrashReason(logging_internal::CrashReason* reason);

  // Counts of messages sent at each priority:
  static int64_t num_messages_[NUM_SEVERITIES];  // under log_mutex

  // We keep the data in a separate struct so that each instance of
  // LogMessage uses less stack space.
  LogMessageData* allocated_;
  LogMessageData* data_;

  friend class LogDestination;

  LogMessage(const LogMessage&);
  void operator=(const LogMessage&);
};

// This class happens to be thread-hostile because all instances share
// a single data buffer, but since it can only be created just before
// the process dies, we don't worry so much.
class GOOGLE_GLOG_DLL_DECL LogMessageFatal : public LogMessage {
 public:
  LogMessageFatal(const char* file, int line);
  LogMessageFatal(const char* file, int line, const CheckOpString& result);
  ATTRIBUTE_NORETURN ~LogMessageFatal();
};

// A non-macro interface to the log facility; (useful
// when the logging level is not a compile-time constant).
inline void LogAtLevel(int const severity, std::string const& msg) {
  LogMessage(__FILE__, __LINE__, severity).stream() << msg;
}

// A macro alternative of LogAtLevel. New code may want to use this
// version since there are two advantages: 1. this version outputs the
// file name and the line number where this macro is put like other
// LOG macros, 2. this macro can be used as C++ stream.
#define LOG_AT_LEVEL(severity) \
  google::LogMessage(__FILE__, __LINE__, severity).stream()

// Check if it's compiled in C++11 mode.
//
// GXX_EXPERIMENTAL_CXX0X is defined by gcc and clang up to at least
// gcc-4.7 and clang-3.1 (2011-12-13).  __cplusplus was defined to 1
// in gcc before 4.7 (Crosstool 16) and clang before 3.1, but is
// defined according to the language version in effect thereafter.
// Microsoft Visual Studio 14 (2015) sets __cplusplus==199711 despite
// reasonably good C++11 support, so we set LANG_CXX for it and
// newer versions (_MSC_VER >= 1900).
#if (defined(__GXX_EXPERIMENTAL_CXX0X__) || __cplusplus >= 201103L || \
     (defined(_MSC_VER) && _MSC_VER >= 1900))
// Helper for CHECK_NOTNULL().
//
// In C++11, all cases can be handled by a single function. Since the value
// category of the argument is preserved (also for rvalue references),
// member initializer lists like the one below will compile correctly:
//
//   Foo()
//     : x_(CHECK_NOTNULL(MethodReturningUniquePtr())) {}
template <typename T>
T CheckNotNull(const char* file, int line, const char* names, T&& t) {
  if (t == nullptr) {
    LogMessageFatal(file, line, new std::string(names));
  }
  return std::forward<T>(t);
}

#else

// A small helper for CHECK_NOTNULL().
template <typename T>
T* CheckNotNull(const char* file, int line, const char* names, T* t) {
  if (t == NULL) {
    LogMessageFatal(file, line, new std::string(names));
  }
  return t;
}
#endif

// Allow folks to put a counter in the LOG_EVERY_X()'ed messages. This
// only works if ostream is a LogStream. If the ostream is not a
// LogStream you'll get an assert saying as much at runtime.
GOOGLE_GLOG_DLL_DECL std::ostream& operator<<(std::ostream& os,
                                              const PRIVATE_Counter&);

// Derived class for PLOG*() above.
class GOOGLE_GLOG_DLL_DECL ErrnoLogMessage : public LogMessage {
 public:
  ErrnoLogMessage(const char* file, int line, LogSeverity severity, int ctr,
                  void (LogMessage::*send_method)());

  // Postpends ": strerror(errno) [errno]".
  ~ErrnoLogMessage();

 private:
  ErrnoLogMessage(const ErrnoLogMessage&);
  void operator=(const ErrnoLogMessage&);
};

// 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 GOOGLE_GLOG_DLL_DECL LogMessageVoidify {
 public:
  LogMessageVoidify() {}
  // This has to be an operator with a precedence lower than << but
  // higher than ?:
  void operator&(std::ostream&) {}
};

// Flushes all log files that contains messages that are at least of
// the specified severity level.  Thread-safe.
GOOGLE_GLOG_DLL_DECL void FlushLogFiles(LogSeverity min_severity);

// Flushes all log files that contains messages that are at least of
// the specified severity level. Thread-hostile because it ignores
// locking -- used for catastrophic failures.
GOOGLE_GLOG_DLL_DECL void FlushLogFilesUnsafe(LogSeverity min_severity);

//
// Set the destination to which a particular severity level of log
// messages is sent.  If base_filename is "", it means "don't log this
// severity".  Thread-safe.
//
GOOGLE_GLOG_DLL_DECL void SetLogDestination(LogSeverity severity,
                                            const char* base_filename);

//
// Set the basename of the symlink to the latest log file at a given
// severity.  If symlink_basename is empty, do not make a symlink.  If
// you don't call this function, the symlink basename is the
// invocation name of the program.  Thread-safe.
//
GOOGLE_GLOG_DLL_DECL void SetLogSymlink(LogSeverity severity,
                                        const char* symlink_basename);

//
// Used to send logs to some other kind of destination
// Users should subclass LogSink and override send to do whatever they want.
// Implementations must be thread-safe because a shared instance will
// be called from whichever thread ran the LOG(XXX) line.
class GOOGLE_GLOG_DLL_DECL LogSink {
 public:
  virtual ~LogSink();

  // Sink's logging logic (message_len is such as to exclude '\n' at the end).
  // This method can't use LOG() or CHECK() as logging system mutex(s) are held
  // during this call.
  virtual void send(LogSeverity severity, const char* full_filename,
                    const char* base_filename, int line,
                    const struct ::tm* tm_time, const char* message,
                    size_t message_len) = 0;

  // Redefine this to implement waiting for
  // the sink's logging logic to complete.
  // It will be called after each send() returns,
  // but before that LogMessage exits or crashes.
  // By default this function does nothing.
  // Using this function one can implement complex logic for send()
  // that itself involves logging; and do all this w/o causing deadlocks and
  // inconsistent rearrangement of log messages.
  // E.g. if a LogSink has thread-specific actions, the send() method
  // can simply add the message to a queue and wake up another thread that
  // handles real logging while itself making some LOG() calls;
  // WaitTillSent() can be implemented to wait for that logic to complete.
  // See our unittest for an example.
  virtual void WaitTillSent();

  // Returns the normal text output of the log message.
  // Can be useful to implement send().
  static std::string ToString(LogSeverity severity, const char* file, int line,
                              const struct ::tm* tm_time, const char* message,
                              size_t message_len);
};

// Add or remove a LogSink as a consumer of logging data.  Thread-safe.
GOOGLE_GLOG_DLL_DECL void AddLogSink(LogSink* destination);
GOOGLE_GLOG_DLL_DECL void RemoveLogSink(LogSink* destination);

//
// Specify an "extension" added to the filename specified via
// SetLogDestination.  This applies to all severity levels.  It's
// often used to append the port we're listening on to the logfile
// name.  Thread-safe.
//
GOOGLE_GLOG_DLL_DECL void SetLogFilenameExtension(
    const char* filename_extension);

//
// Make it so that all log messages of at least a particular severity
// are logged to stderr (in addition to logging to the usual log
// file(s)).  Thread-safe.
//
GOOGLE_GLOG_DLL_DECL void SetStderrLogging(LogSeverity min_severity);

//
// Make it so that all log messages go only to stderr.  Thread-safe.
//
GOOGLE_GLOG_DLL_DECL void LogToStderr();

GOOGLE_GLOG_DLL_DECL const std::vector<std::string>& GetLoggingDirectories();

// For tests only:  Clear the internal [cached] list of logging directories to
// force a refresh the next time GetLoggingDirectories is called.
// Thread-hostile.
void TestOnly_ClearLoggingDirectoriesList();

// Returns a set of existing temporary directories, which will be a
// subset of the directories returned by GetLogginDirectories().
// Thread-safe.
GOOGLE_GLOG_DLL_DECL void GetExistingTempDirectories(
    std::vector<std::string>* list);

// Print any fatal message again -- useful to call from signal handler
// so that the last thing in the output is the fatal message.
// Thread-hostile, but a race is unlikely.
GOOGLE_GLOG_DLL_DECL void ReprintFatalMessage();

// Return the string representation of the provided LogSeverity level.
// Thread-safe.
GOOGLE_GLOG_DLL_DECL const char* GetLogSeverityName(LogSeverity severity);

// ---------------------------------------------------------------------
// Implementation details that are not useful to most clients
// ---------------------------------------------------------------------

// A Logger is the interface used by logging modules to emit entries
// to a log.  A typical implementation will dump formatted data to a
// sequence of files.  We also provide interfaces that will forward
// the data to another thread so that the invoker never blocks.
// Implementations should be thread-safe since the logging system
// will write to them from multiple threads.

namespace base {

class GOOGLE_GLOG_DLL_DECL Logger {
 public:
  virtual ~Logger();

  // Writes "message[0,message_len-1]" corresponding to an event that
  // occurred at "timestamp".  If "force_flush" is true, the log file
  // is flushed immediately.
  //
  // The input message has already been formatted as deemed
  // appropriate by the higher level logging facility.  For example,
  // textual log messages already contain timestamps, and the
  // file:linenumber header.
  virtual void Write(bool force_flush, time_t timestamp, const char* message,
                     int message_len) = 0;

  // Flush any buffered messages
  virtual void Flush() = 0;

  // Get the current LOG file size.
  // The returned value is approximate since some
  // logged data may not have been flushed to disk yet.
  virtual uint32_t LogSize() = 0;
};

// Get the logger for the specified severity level.  The logger
// remains the property of the logging module and should not be
// deleted by the caller.  Thread-safe.
extern GOOGLE_GLOG_DLL_DECL Logger* GetLogger(LogSeverity level);

// Set the logger for the specified severity level.  The logger
// becomes the property of the logging module and should not
// be deleted by the caller.  Thread-safe.
extern GOOGLE_GLOG_DLL_DECL void SetLogger(LogSeverity level, Logger* logger);

}  // namespace base

// glibc has traditionally implemented two incompatible versions of
// strerror_r(). There is a poorly defined convention for picking the
// version that we want, but it is not clear whether it even works with
// all versions of glibc.
// So, instead, we provide this wrapper that automatically detects the
// version that is in use, and then implements POSIX semantics.
// N.B. In addition to what POSIX says, we also guarantee that "buf" will
// be set to an empty string, if this function failed. This means, in most
// cases, you do not need to check the error code and you can directly
// use the value of "buf". It will never have an undefined value.
// DEPRECATED: Use StrError(int) instead.
GOOGLE_GLOG_DLL_DECL int posix_strerror_r(int err, char* buf, size_t len);

// A thread-safe replacement for strerror(). Returns a string describing the
// given POSIX error code.
GOOGLE_GLOG_DLL_DECL std::string StrError(int err);

// A class for which we define operator<<, which does nothing.
class GOOGLE_GLOG_DLL_DECL NullStream : public LogMessage::LogStream {
 public:
  // Initialize the LogStream so the messages can be written somewhere
  // (they'll never be actually displayed). This will be needed if a
  // NullStream& is implicitly converted to LogStream&, in which case
  // the overloaded NullStream::operator<< will not be invoked.
  NullStream() : LogMessage::LogStream(message_buffer_, 1, 0) {}
  NullStream(const char* /*file*/, int /*line*/,
             const CheckOpString& /*result*/)
      : LogMessage::LogStream(message_buffer_, 1, 0) {}
  NullStream& stream() { return *this; }

 private:
  // A very short buffer for messages (which we discard anyway). This
  // will be needed if NullStream& converted to LogStream& (e.g. as a
  // result of a conditional expression).
  char message_buffer_[2];
};

// Do nothing. This operator is inline, allowing the message to be
// compiled away. The message will not be compiled away if we do
// something like (flag ? LOG(INFO) : LOG(ERROR)) << message; when
// SKIP_LOG=WARNING. In those cases, NullStream will be implicitly
// converted to LogStream and the message will be computed and then
// quietly discarded.
template <class T>
inline NullStream& operator<<(NullStream& str, const T&) {
  return str;
}

// Similar to NullStream, but aborts the program (without stack
// trace), like LogMessageFatal.
class GOOGLE_GLOG_DLL_DECL NullStreamFatal : public NullStream {
 public:
  NullStreamFatal() {}
  NullStreamFatal(const char* file, int line, const CheckOpString& result)
      : NullStream(file, line, result) {}
  ATTRIBUTE_NORETURN ~NullStreamFatal() throw() { _exit(1); }
};
}  // namespace google

#endif  // OR_TOOLS_BASE_LOGGING_H_