12muduo_base库源码分析（三）

最新推荐文章于 2024-05-25 23:16:02 发布

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本文介绍了一个基于C++的异常处理类的设计与实现，通过具体的代码示例展示了如何捕获和记录异常信息，包括错误消息及堆栈跟踪。

1.Exception类实现

（1）backtrace，栈回溯，保存各个栈帧的地址

（2)backtrace_symbols，根据地址，转成相应的函数符号

（3）abi::__cxa_demangle

2.代码

Exception.h

// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#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 demangle(const char* symbol);

  string message_;
  string stack_;
};

}

#endif  // MUDUO_BASE_EXCEPTION_H

Exception.cc

// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include <muduo/base/Exception.h>

#include <cxxabi.h>
#include <execinfo.h>
#include <stdlib.h>
#include <stdio.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_.append(demangle(strings[i]));
      stack_.push_back('\n');
    }
    free(strings);
  }
}

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;
}

Exception_test.cpp

#include <muduo/base/Exception.h>
#include <stdio.h>

class Bar
{
 public:
  void test()
  {
    throw muduo::Exception("oops");
  }
};

void foo()
{
  Bar b;
  b.test();
}

int main()
{
  try
  {
    foo();
  }
  catch (const muduo::Exception& ex)
  {
    printf("reason: %s\n", ex.what());
    printf("stack trace: %s\n", ex.stackTrace());
  }
}