Exception类实现（12）

Exception 类图

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-message_: string   -stack_:string   <<create>>-Exception(what:char)   <<create>>-Exception(what:string)   <<destroy>>-Exception()   +what():const char *   +stackTrace():const char*   -fillStackTrace ():void

下面是源代码：

头文件：

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#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_; };   }   #endif  // MUDUO_BASE_EXCEPTION_

源文件

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// 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>   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(); }   //填充错误堆栈 void Exception::fillStackTrace() {   const int len = 200;   void* buffer[len];   /*    backtrace()  returns  a  backtrace  for the calling program, in the array pointed to by buffer.  A backtrace is the series of currently    active function calls for the program.  Each item in the array pointed to by buffer is of type void *, and is the return  address  from    the corresponding stack frame.  The size argument specifies the maximum number of addresses that can be stored in buffer.   */   //buffer 存地就是函数的地址   int nptrs = ::backtrace(buffer, len);   /*             Given  the  set  of  addresses returned by backtrace() in buffer, backtrace_symbols() translates the addresses into an array of strings         that describe the addresses symbolically.  The size argument specifies the number of addresses in buffer.  The symbolic  representation        of  each  address  consists  of  the  function name (if this can be determined), a hexadecimal offset into the function, and the actual        return address (in hexadecimal).  The address of the array of string pointers is returned as  the  function  result  of  backtrace_sym-        bols().   This  array  is malloc(3)ed by backtrace_symbols(), and must be freed by the caller.  (The strings pointed to by the array of        pointers need not and should not be freed.)   Pointer--------pointer1 ------string --------------pointer2 ------string --------------pointer3 ------string --------------pointer4 ------string --------------pointer5 ------string --------------pointer6 ------string   我们要释放pointer占用的内存，但是pointer所指向的内存不需要我们释放 free (Pointer) 就OK了   */   //将buffer里面的地址转换为函数符号，也可以所说函数的名字   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');     }     //这个要自己释放     free(strings);   } }

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测试程序

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#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());   } }

程序输出：

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reason: oops stack trace: muduo::Exception::fillStackTrace() muduo::Exception::Exception(char const*) Bar::test() foo() ./exception_test(main+0x10) /lib/libc.so.6(__libc_start_main+0xe6) ./exception_test()