muduo庫源碼學習(base)Exception

class Exception : public std::exception
{
 public:
  explicit Exception(const char* what);
  explicit Exception(const string& what);
  virtual ~Exception() throw();
  virtual const char* what() const throw();
  const char* stackTrace() const throw();

 private:
  void fillStackTrace();

  string message_;
  string stack_;
};

Exception::Exception(const char* msg)
  : message_(msg)
{
  fillStackTrace();
}

Exception::Exception(const string& msg)
  : message_(msg)
{
  fillStackTrace();
}

Exception::~Exception() throw ()
{
}

const char* Exception::what() const throw()
{
  return message_.c_str();
}

const char* Exception::stackTrace() const throw()
{
  return stack_.c_str();
}

void Exception::fillStackTrace()
{
  const int len = 200;
  void* buffer[len];
  //該函數用於獲取當前線程的調用堆棧,獲取的信息將會被存放在buffer中,它是一個指針數組
  int nptrs = ::backtrace(buffer, len);//猜測是得到trace的數量，每個trace存到buffer[i]裏，即從[0]到[nptrs-1]
  char** strings = ::backtrace_symbols(buffer, nptrs);//直接返回這個buffer內的可打印信息
  if (strings)
  {
    for (int i = 0; i < nptrs; ++i)
    {
      // TODO demangle funcion name with abi::__cxa_demangle
      stack_.append(strings[i]);
      stack_.push_back('\n');
    }
    free(strings);//直接free即可！也就是說malloc的是一個一維數組，只是邏輯成二維；
  }
}