1 Exception類

Exception類包括兩個檔案 :Exception.cc, Exception.h。

1.1 Exception.h

#ifndef MUDUO_BASE_EXCEPTION_H
#define MUDUO_BASE_EXCEPTION_H

#include <muduo/base/Types.h>
#include <exception>

namespace muduo
{

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_;
};

}

1.2 Exception.cc

#include <muduo/base/Exception.h>

//#include <cxxabi.h>
#include <execinfo.h>
#include <stdlib.h>

using namespace muduo;

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];
  int nptrs = ::backtrace(buffer, len);
  char** strings = ::backtrace_symbols(buffer, nptrs);
  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);
  }
}

2 backtrace函式

int backtrace(void **buffer, int size); 棧回溯，儲存各個棧幀的地址;
buffer這個指標指向了一個陣列，陣列中的每一項都是void *型別，用來儲存函式的地址。

3 backtrace_symbols函式

char **backtrace_symbols(void const buffer, int size);根據地址，轉成相應的函式符號；
char strings = ::backtrace_symbols(buffer, nptrs);返回的是指標的指標；

4 還原C++函式的真實的名稱

需要的標頭檔案是<cxxabi.h>和<stdio.h>

string Exception::demangle(const char* symbol)
{
  size_t size;
  int status;
  char temp[128];
  char* demangled;
  //first, try to demangle a c++ name
  if (1 == sscanf(symbol, "%*[^(]%*[^_]%127[^)+]", temp)) {
    if (NULL != (demangled = abi::__cxa_demangle(temp, NULL, &size, &status))) {
      string result(demangled);
      free(demangled);
      return result;
    }
  }
  //if that didn't work, try to get a regular c symbol
  if (1 == sscanf(symbol, "%127s", temp)) {
    return temp;
  }
 
  //if all else fails, just return the symbol
  return symbol;
}

修改fillStackTrace()

void Exception::fillStackTrace()
{
  const int len = 200;
  void* buffer[len];
  int nptrs = ::backtrace(buffer, len);
  char** strings = ::backtrace_symbols(buffer, nptrs);
  if (strings)
  {
    for (int i = 0; i < nptrs; ++i)
    {
      // TODO demangle funcion name with abi::__cxa_demangle
      stack_.append(demangle(strings[i]));
      stack_.push_back('\n');
    }
    free(strings);
  }
}