muduo网络库源码学习————日志类封装

muduo库里面的日志使方法如下

这里定义了一个宏
#define LOG_INFO if (muduo::Logger::logLevel() <= muduo::Logger::INFO) \
  muduo::Logger(__FILE__, __LINE__).stream()
返回的stream重载了一系列的运算符，使用方法如下
LOG_INFO<<“info ...”;   // 使用方式
上面那句其实就是
muduo::Logger(__FILE__, __LINE__).stream()<<“info”;

调用过程实际是如下所示的
Logger => Impl => LogStream => operator<< FixedBuffer => g_output => g_flush
muduo库里面的日志类封装相关的文件为Logging.h，Logging.cc，LogSrtream.h，LogSrtream.cc，附带一个StringPiece.h文件，几个文件的注解如下所示：
Logging.h

//日志输出
#ifndef MUDUO_BASE_LOGGING_H
#define MUDUO_BASE_LOGGING_H

#include <muduo/base/LogStream.h>
#include <muduo/base/Timestamp.h>

namespace muduo
{

class Logger
{
 public:
    //日志级别
  enum LogLevel
  {
    TRACE,
    DEBUG,
    INFO,
    WARN,
    ERROR,
    FATAL,
    NUM_LOG_LEVELS,//级别个数6
  };

  // compile time calculation of basename of source file
  class SourceFile
  {
   public:
    template<int N>
    inline SourceFile(const char (&arr)[N])
      : data_(arr),
        size_(N-1)
    {
      const char* slash = strrchr(data_, '/'); // builtin function
      if (slash)
      {
        data_ = slash + 1;
        size_ -= static_cast<int>(data_ - arr);
      }
    }

    explicit SourceFile(const char* filename)
      : data_(filename)
    {
      const char* slash = strrchr(filename, '/');
      if (slash)
      {
        data_ = slash + 1;
      }
      size_ = static_cast<int>(strlen(data_));
    }

    const char* data_;
    int size_;
  };
//四个构造函数
  Logger(SourceFile file, int line);
  Logger(SourceFile file, int line, LogLevel level);
  Logger(SourceFile file, int line, LogLevel level, const char* func);
  Logger(SourceFile file, int line, bool toAbort);
  ~Logger();

  LogStream& stream() { return impl_.stream_; }

  static LogLevel logLevel();
  static void setLogLevel(LogLevel level);

  typedef void (*OutputFunc)(const char* msg, int len);
  typedef void (*FlushFunc)();
  static void setOutput(OutputFunc);
  static void setFlush(FlushFunc);

 private:
//Loger类的内部嵌套类
//Impl类主要是负责日志的格式化
class Impl
{
 public:
  typedef Logger::LogLevel LogLevel;
  //构造函数
  Impl(LogLevel level, int old_errno, const SourceFile& file, int line);
  //格式化时间函数
  void formatTime();
  void finish();

  Timestamp time_;//Timestamp时间戳
  LogStream stream_;//LogStream类对象成员
  LogLevel level_;//日志级别
  int line_;//行号
  SourceFile basename_;
};

  Impl impl_;//Impl类对象成员

};

extern Logger::LogLevel g_logLevel;

inline Logger::LogLevel Logger::logLevel()
{
  return g_logLevel;//日志级别
}
//日志输出宏，输出在哪个文件? 哪一行? 哪个函数? 哪种级别?
//无名对象所在语句执行后就立即被析构，然后调用析构函数将缓冲区的内容分输出  
// muduo::Logger(__FILE__, __LINE__, muduo::Logger::TRACE, __func__).stream()返回的是一个LogStream对象
#define LOG_TRACE if (muduo::Logger::logLevel() <= muduo::Logger::TRACE) \
  muduo::Logger(__FILE__, __LINE__, muduo::Logger::TRACE, __func__).stream()
#define LOG_DEBUG if (muduo::Logger::logLevel() <= muduo::Logger::DEBUG) \
  muduo::Logger(__FILE__, __LINE__, muduo::Logger::DEBUG, __func__).stream()
#define LOG_INFO if (muduo::Logger::logLevel() <= muduo::Logger::INFO) \
  muduo::Logger(__FILE__, __LINE__).stream()
#define LOG_WARN muduo::Logger(__FILE__, __LINE__, muduo::Logger::WARN).stream()
#define LOG_ERROR muduo::Logger(__FILE__, __LINE__, muduo::Logger::ERROR).stream()
#define LOG_FATAL muduo::Logger(__FILE__, __LINE__, muduo::Logger::FATAL).stream()
//false表示不会退出程序
#define LOG_SYSERR muduo::Logger(__FILE__, __LINE__, false).stream()//ERROR
//true表示会退出程序
#define LOG_SYSFATAL muduo::Logger(__FILE__, __LINE__, true).stream()//FATAL

const char* strerror_tl(int savedErrno);

// Taken from glog/logging.h
//
// Check that the input is non NULL.  This very useful in constructor
// initializer lists.

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

// A small helper for CHECK_NOTNULL().
template <typename T>
T* CheckNotNull(Logger::SourceFile file, int line, const char *names, T* ptr) {
  if (ptr == NULL) {
   Logger(file, line, Logger::FATAL).stream() << names;
  }
  return ptr;
}

}

#endif  // MUDUO_BASE_LOGGING_H

Logging.cc

#include <muduo/base/Logging.h>

#include <muduo/base/CurrentThread.h>
#include <muduo/base/StringPiece.h>
#include <muduo/base/Timestamp.h>

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

#include <sstream>

namespace muduo
{

/*
class LoggerImpl
{
 public:
  typedef Logger::LogLevel LogLevel;
  LoggerImpl(LogLevel level, int old_errno, const char* file, int line);
  void finish();

  Timestamp time_;
  LogStream stream_;
  LogLevel level_;
  int line_;
  const char* fullname_;
  const char* basename_;
};
*/


__thread char t_errnobuf[512];
__thread char t_time[32];
__thread time_t t_lastSecond;

const char* strerror_tl(int savedErrno)
{
  return strerror_r(savedErrno, t_errnobuf, sizeof t_errnobuf);
}
//初始化日志级别
Logger::LogLevel initLogLevel()
{//获取环境变量
  if (::getenv("MUDUO_LOG_TRACE"))//如果获取到了这个环境变量
    return Logger::TRACE;//日志级别为TRACE
  else if (::getenv("MUDUO_LOG_DEBUG"))//如果获取到了这个环境变量
    return Logger::DEBUG;//日志级别为DEBUG
  else
    return Logger::INFO;//否则日志级别为INFO
}

Logger::LogLevel g_logLevel = initLogLevel();
//日志级别
const char* LogLevelName[Logger::NUM_LOG_LEVELS] =
{
  "TRACE ",
  "DEBUG ",
  "INFO  ",
  "WARN  ",
  "ERROR ",
  "FATAL ",
};

// helper class for known string length at compile time
class T
{
 public:
  T(const char* str, unsigned len)
    :str_(str),
     len_(len)
  {
    assert(strlen(str) == len_);
  }

  const char* str_;
  const unsigned len_;
};

inline LogStream& operator<<(LogStream& s, T v)
{
  s.append(v.str_, v.len_);
  return s;
}

inline LogStream& operator<<(LogStream& s, const Logger::SourceFile& v)
{
  s.append(v.data_, v.size_);
  return s;
}
//默认输出
void defaultOutput(const char* msg, int len)
{//输出到标准输出
  size_t n = fwrite(msg, 1, len, stdout);
  //FIXME check n
  (void)n;
}
//默认清空
void defaultFlush()
{//默认清空标准输出
  fflush(stdout);
}

Logger::OutputFunc g_output = defaultOutput;
Logger::FlushFunc g_flush = defaultFlush;

}

using namespace muduo;
//Impl类的构造函数
//级别，错误(没有错误则传0),文件，行
//Impl类主要是负责日志的格式化
Logger::Impl::Impl(LogLevel level, int savedErrno, const SourceFile& file, int line)
  : time_(Timestamp::now()),//登记当前的时间
    stream_(),//LogStream类
    level_(level),//级别
    line_(line),//行
    basename_(file)//文件名称
{
  formatTime();//格式化时间
  CurrentThread::tid();//缓存当前线程的id
  //输出字符串格式的线程id
  stream_ << T(CurrentThread::tidString(), 6);
  stream_ << T(LogLevelName[level], 6);
  if (savedErrno != 0)//如果savedErrno不为零，还要输出对应的信息
  {
    stream_ << strerror_tl(savedErrno) << " (errno=" << savedErrno << ") ";
  }
}

void Logger::Impl::formatTime()
{
  int64_t microSecondsSinceEpoch = time_.microSecondsSinceEpoch();//获得微秒格式的时间
  time_t seconds = static_cast<time_t>(microSecondsSinceEpoch / 1000000);//获得秒
  int microseconds = static_cast<int>(microSecondsSinceEpoch % 1000000);//微秒
  if (seconds != t_lastSecond)
  {
    t_lastSecond = seconds;
    struct tm tm_time;
    ::gmtime_r(&seconds, &tm_time); // FIXME TimeZone::fromUtcTime

    int len = snprintf(t_time, sizeof(t_time), "%4d%02d%02d %02d:%02d:%02d",
        tm_time.tm_year + 1900, tm_time.tm_mon + 1, tm_time.tm_mday,
        tm_time.tm_hour, tm_time.tm_min, tm_time.tm_sec);
    assert(len == 17); (void)len;
  }
  Fmt us(".%06dZ ", microseconds);
  assert(us.length() == 9);
  //LogStream类重载运算符，把信息输出到缓冲区
  stream_ << T(t_time, 17) << T(us.data(), 9);
}

void Logger::Impl::finish()
{
  stream_ << " - " << basename_ << ':' << line_ << '\n';
}
//构造函数，都是构造Impl对象
Logger::Logger(SourceFile file, int line) : impl_(INFO, 0, file, line)
{
}
//文件名，行，级别，函数名称
Logger::Logger(SourceFile file, int line, LogLevel level, const char* func) : impl_(level, 0, file, line)
{//格式化函数名称
  impl_.stream_ << func << ' ';
}

Logger::Logger(SourceFile file, int line, LogLevel level): impl_(level, 0, file, line)
{
}
//如果toAbort是真，则级别为FATAL，否则为ERROR
Logger::Logger(SourceFile file, int line, bool toAbort) : impl_(toAbort?FATAL:ERROR, errno, file, line)
{
}
//析构函数
Logger::~Logger()
{
  impl_.finish();
  //取出stream类缓冲区的内容放到buf
  const LogStream::Buffer& buf(stream().buffer());
  //输出，g_output有一个默认的输出stdout
  g_output(buf.data(), buf.length());
  if (impl_.level_ == FATAL)//如果是FATAL
  {
    g_flush();//清空缓冲区
    abort();//终止程序
  }
}

void Logger::setLogLevel(Logger::LogLevel level)
{
  g_logLevel = level;
}
//更改输出函数
void Logger::setOutput(OutputFunc out)
{
  g_output = out;
}

void Logger::setFlush(FlushFunc flush)
{
  g_flush = flush;
}

LogSrtream.h

//日志流
#ifndef MUDUO_BASE_LOGSTREAM_H
#define MUDUO_BASE_LOGSTREAM_H

#include <muduo/base/StringPiece.h>
#include <muduo/base/Types.h>
#include <assert.h>
#include <string.h> // memcpy
#ifndef MUDUO_STD_STRING
#include <string>
#endif
#include <boost/noncopyable.hpp>

namespace muduo
{

namespace detail
{
//定义两个缓冲区大小的常量
const int kSmallBuffer = 4000;
const int kLargeBuffer = 4000*1000;
//缓冲区类
//模板，但是SIZE是非类型参数
template<int SIZE>
class FixedBuffer : boost::noncopyable//不可被拷贝
{
 public:
    //构造函数
  FixedBuffer() : cur_(data_)//初始化当前指针
  {//设置函数指针
    setCookie(cookieStart);
  }
//析构函数
  ~FixedBuffer()
  {//传递函数指针，这个和构造函数传递的两个函数在下面
    setCookie(cookieEnd);
  }
//添加数据
  void append(const char* /*restrict*/ buf, size_t len)
  {
    // FIXME: append partially当前可用空间长度大于len
    if (implicit_cast<size_t>(avail()) > len)
    {//复制数据
      memcpy(cur_, buf, len);
      //更新当前指针
      cur_ += len;
    }
    //如果当前空间不够用了，这里并没有实现添加部分进来
  }

  const char* data() const { return data_; }
  //已经用的长度空间
  int length() const { return static_cast<int>(cur_ - data_); }
  // write to data_ directly
  char* current() { return cur_; }
  //当前可用的空间(end减去当前指针)
  int avail() const { return static_cast<int>(end() - cur_); }
  //增加  
  void add(size_t len) { cur_ += len; }
  //重置空间
  void reset() { cur_ = data_; }
  //把数据都清零，相当于memset(buf,0,sizeof(buf))
  void bzero() { ::bzero(data_, sizeof data_); }
  // for used by GDB
  //在数据后面加个结束符
  const char* debugString();
  //将函数指针指向传递进来的函数
  void setCookie(void (*cookie)()) { cookie_ = cookie; }
  // for used by unit test
  //把数据构造一个String对象出来
  string asString() const { return string(data_, length()); }

 private:
    //返回的是缓冲区的后一个地址
  const char* end() const { return data_ + sizeof data_; }
  // Must be outline function for cookies.
  static void cookieStart();
  static void cookieEnd();

  void (*cookie_)();//一个函数指针
  char data_[SIZE];//data就是缓冲区,容量为传进来的SIZE
  char* cur_;//当前指针
};

}
//LogStream类主要是封装了插入运算符
class LogStream : boost::noncopyable
{
  typedef LogStream self;
 public:
    //包含了LogStream的缓冲区，kSmallBuffer，k开头的表示一个常量，是谷歌的编程规范
  typedef detail::FixedBuffer<detail::kSmallBuffer> Buffer;
   //输出数据首先是输出到缓冲区当中
   //以下重载了各种类型的插入运算符
   //返回的是自身的引用
  self& operator<<(bool v)
  {//输出布尔类型
    buffer_.append(v ? "1" : "0", 1);//长度是1
    return *this;
  }
  //实现在.cc文件
  self& operator<<(short);
  self& operator<<(unsigned short);
  self& operator<<(int);
  self& operator<<(unsigned int);
  self& operator<<(long);
  self& operator<<(unsigned long);
  self& operator<<(long long);
  self& operator<<(unsigned long long);
    //存放指针
  self& operator<<(const void*);
  //浮点数
  self& operator<<(float v)
  {
    *this << static_cast<double>(v);
    return *this;
  }
  self& operator<<(double);
  // self& operator<<(long double);
 //存放单个字符
  self& operator<<(char v)
  {
    buffer_.append(&v, 1);
    return *this;
  }

  // self& operator<<(signed char);
  // self& operator<<(unsigned char);
 //存放字符串
  self& operator<<(const char* v)
  {//把字符串添加进缓冲区
    buffer_.append(v, strlen(v));
    return *this;
  }

  self& operator<<(const string& v)
  {
    buffer_.append(v.c_str(), v.size());
    return *this;
  }
//如果定义了MUDUO_STD_STRING，则使用的是std::string
//否则使用的是__gnu_cxx::__sso_string
#ifndef MUDUO_STD_STRING
  self& operator<<(const std::string& v)
  {
    buffer_.append(v.c_str(), v.size());
    return *this;
  }
#endif

  self& operator<<(const StringPiece& v)
  {
    buffer_.append(v.data(), v.size());
    return *this;
  }
  //这三个只是改装了以下接口
  void append(const char* data, int len) { buffer_.append(data, len); }
  const Buffer& buffer() const { return buffer_; }
  void resetBuffer() { buffer_.reset(); }

 private:
  void staticCheck();
//成员模板函数
  template<typename T>
  void formatInteger(T);

  Buffer buffer_;//大小为kSmallBuffer的缓冲区

  static const int kMaxNumericSize = 32;
};

class Fmt // : boost::noncopyable
{
 public:
    //成员模板，把val进行格式化，然后存放到buf中
  template<typename T>
  Fmt(const char* fmt, T val);

  const char* data() const { return buf_; }//返回格式化的数据
  int length() const { return length_; }//返回长度

 private:
  char buf_[32];
  int length_;
};

inline LogStream& operator<<(LogStream& s, const Fmt& fmt)
{
  s.append(fmt.data(), fmt.length());
  return s;
}

}
#endif  // MUDUO_BASE_LOGSTREAM_H

LogSrtream.cc

#include <muduo/base/LogStream.h>

#include <algorithm>
#include <limits>
#include <boost/static_assert.hpp>
#include <boost/type_traits/is_arithmetic.hpp>
#include <assert.h>
#include <string.h>
#include <stdint.h>
#include <stdio.h>

using namespace muduo;
using namespace muduo::detail;

#pragma GCC diagnostic ignored "-Wtype-limits"
//#pragma GCC diagnostic error "-Wtype-limits"
namespace muduo
{
namespace detail
{

const char digits[] = "9876543210123456789";
const char* zero = digits + 9;//digits + 9就是"0"
BOOST_STATIC_ASSERT(sizeof(digits) == 20);

const char digitsHex[] = "0123456789ABCDEF";
BOOST_STATIC_ASSERT(sizeof digitsHex == 17);

// Efficient Integer to String Conversions, by Matthew Wilson.
//将 一个数转换成字符串
template<typename T>
size_t convert(char buf[], T value)
{
  T i = value;
  char* p = buf;

  do
  {//对10取模得到最后一位数字
    int lsd = static_cast<int>(i % 10);
    i /= 10;//更新当前数
    //zero将数字转换成字符串,zero指针指向的字符是0，再偏移lsd个位置可以得到相应的字符
    *p++ = zero[lsd];
  } while (i != 0);
//比如-123会转成"321-"
  if (value < 0)//如果要转换的值小于0
  {
    *p++ = '-';
  }
  *p = '\0';//添加结束符
  std::reverse(buf, p);//使用reverse将字符串进行逆转

  return p - buf;//返回转换的字符数
}

//uintptr_t类型对于32位平台来说就是unsigned int
//对于64位平台来说就是unsigned long int
size_t convertHex(char buf[], uintptr_t value)
{//转换成16进制的字符，和转换成10进制的差不多
  uintptr_t i = value;
  char* p = buf;
  do
  {
    int lsd = i % 16;
    i /= 16;
    *p++ = digitsHex[lsd];
  } while (i != 0);

  *p = '\0';
  std::reverse(buf, p);

  return p - buf;
}

}
}
//在数据后面加个\0，相当于字符串
template<int SIZE>
const char* FixedBuffer<SIZE>::debugString()
{
  *cur_ = '\0';//加入结束符
  return data_;
}

template<int SIZE>
void FixedBuffer<SIZE>::cookieStart()
{
}

template<int SIZE>
void FixedBuffer<SIZE>::cookieEnd()
{
}

template class FixedBuffer<kSmallBuffer>;
template class FixedBuffer<kLargeBuffer>;

void LogStream::staticCheck()
{
  BOOST_STATIC_ASSERT(kMaxNumericSize - 10 > std::numeric_limits<double>::digits10);
  BOOST_STATIC_ASSERT(kMaxNumericSize - 10 > std::numeric_limits<long double>::digits10);
  BOOST_STATIC_ASSERT(kMaxNumericSize - 10 > std::numeric_limits<long>::digits10);
  BOOST_STATIC_ASSERT(kMaxNumericSize - 10 > std::numeric_limits<long long>::digits10);
}
//类型转换成员模板的实现
template<typename T>
void LogStream::formatInteger(T v)
{//当前缓冲区大于32
  if (buffer_.avail() >= kMaxNumericSize)//kMaxNumericSize为32
  {//把v转换成字符串，存放到buffer_.current()
    size_t len = convert(buffer_.current(), v);
    //调整buffer_.current()指针
    buffer_.add(len);
  }
}
//重载各种运算符
LogStream& LogStream::operator<<(short v)
{//short转成int
  *this << static_cast<int>(v);
  return *this;
}

LogStream& LogStream::operator<<(unsigned short v)
{//unsigned short转成unsigned int
  *this << static_cast<unsigned int>(v);
  return *this;
}

LogStream& LogStream::operator<<(int v)
{
  formatInteger(v);
  return *this;
}

LogStream& LogStream::operator<<(unsigned int v)
{
  formatInteger(v);
  return *this;
}

LogStream& LogStream::operator<<(long v)
{
  formatInteger(v);
  return *this;
}

LogStream& LogStream::operator<<(unsigned long v)
{
  formatInteger(v);
  return *this;
}

LogStream& LogStream::operator<<(long long v)
{
  formatInteger(v);
  return *this;
}

LogStream& LogStream::operator<<(unsigned long long v)
{
  formatInteger(v);
  return *this;
}
//转换指针，是转成16进制的
LogStream& LogStream::operator<<(const void* p)
{//把指针强制转换为uintptr_t类型
//uintptr_t类型对于32位平台来说就是unsigned int
//对于64位平台来说就是unsigned long int
  uintptr_t v = reinterpret_cast<uintptr_t>(p);
  if (buffer_.avail() >= kMaxNumericSize)
  {
    char* buf = buffer_.current();//获取当前的位置
    buf[0] = '0';//添加两个字符表示是16进制
    buf[1] = 'x';
    size_t len = convertHex(buf+2, v);
    buffer_.add(len+2);//更新当前指针
  }
  return *this;
}

// FIXME: replace this with Grisu3 by Florian Loitsch.
LogStream& LogStream::operator<<(double v)
{
  if (buffer_.avail() >= kMaxNumericSize)
  {
    int len = snprintf(buffer_.current(), kMaxNumericSize, "%.12g", v);
    buffer_.add(len);
  }
  return *this;
}
//把T按fmt格式化后存放到buf中
template<typename T>
Fmt::Fmt(const char* fmt, T val)
{//断言T是算术类型
  BOOST_STATIC_ASSERT(boost::is_arithmetic<T>::value == true);
 //使用snprintf函数进行格式化
  length_ = snprintf(buf_, sizeof buf_, fmt, val);
  assert(static_cast<size_t>(length_) < sizeof buf_);
}

// Explicit instantiations
//模板的特化
template Fmt::Fmt(const char* fmt, char);
template Fmt::Fmt(const char* fmt, short);
template Fmt::Fmt(const char* fmt, unsigned short);
template Fmt::Fmt(const char* fmt, int);
template Fmt::Fmt(const char* fmt, unsigned  int);
template Fmt::Fmt(const char* fmt, long);
template Fmt::Fmt(const char* fmt, unsigned long);
template Fmt::Fmt(const char* fmt, long long);
template Fmt::Fmt(const char* fmt, unsigned long long);
template Fmt::Fmt(const char* fmt, float);
template Fmt::Fmt(const char* fmt, double);

编写两个简单的程序使用下日志功能，Log_test1.cc将日志输出到终端，代码如下

//日志输出到标准输出
#include <muduo/base/Logging.h>
#include <errno.h>

using namespace muduo;

int main()
{   //简单的使用下日志输出
    //各种级别的日志输出
    LOG_TRACE<<"trace ...";
    LOG_DEBUG<<"debug ...";
    LOG_INFO<<"info ...";
    LOG_WARN<<"warn ...";
    LOG_ERROR<<"error ...";
    //LOG_FATAL<<"fatal ...";//这里会中断程序，先注释掉
    errno = 13;
    LOG_SYSERR<<"syserr ...";
    //LOG_SYSFATAL<<"sysfatal ...";//这里会中断程序，先注释掉
    return 0;
}

运行结果如下所示：

Log_test2.cc将日志输出到文件，代码如下所示：

//日志输出到文件
#include <muduo/base/Logging.h>
#include <errno.h>
#include <stdio.h>

using namespace muduo;

FILE* g_file;//定义一个文件
//muduo中的  typedef void (*OutputFunc)(const char* msg, int len);
void dummyOutput(const char* msg, int len)
{
    if (g_file)
    {//将内容写到文件里
        fwrite(msg, 1, len, g_file);
    }
}

void dummyFlush()
{
    fflush(g_file);//清空输出
}

int main()
{
    g_file = ::fopen("/mnt/hgfs/lcw_program/lcw_muduo_learning/tests/muduo_log", "ae");//打开文件
    Logger::setOutput(dummyOutput);//设置输出到文件,dummyOutput为函数
    Logger::setFlush(dummyFlush);

    LOG_TRACE<<"trace ...";
    LOG_DEBUG<<"debug ...";
    LOG_INFO<<"info ...";
    LOG_WARN<<"warn ...";
    LOG_ERROR<<"error ...";
    //LOG_FATAL<<"fatal ...";//这里会中断程序，先注释掉
    errno = 13;
    LOG_SYSERR<<"syserr ...";
    //LOG_SYSFATAL<<"sysfatal ...";

    ::fclose(g_file);//关闭文件

    return 0;
}

运行结果如下：

文件内容如下：