C++编程调试秘笈----读书笔记(2)

二、运行时的错误

一个可以进行安全检查的宏

scpp_assert.h：

#ifndef __SCCP_ASSERT_H__#define __SCCP_ASSERT_H__#include "sstream"#ifdef SCPP_THROW_EXCEPTION_ON_BUG#include "exception"namespace scpp{class ScppAssertFailedException : public std::exception{public:ScppAssertFailedException(const char *file_name, unsigned line_number, const char* message);~ScppAssertFailedException() throw(){};public:virtual const char * what() const throw(){return what_.c_str();}private:std::string what_;};}// namespace scpp#endifvoid SCPP_AssertErrorHandler(const char *file_name, unsigned line_number, const char *message);#define SCPP_ASSERT(condition, msg)\if (!(condition))\{                                               \std::ostringstream s;                       \s << msg;                                   \SCPP_AssertErrorHandler(                    \__FILE__, __LINE__, s.str().c_str());   \}                                               #ifndef _DEBUG#define SCPP_TEST_ASSERT_ON#endif // !_DEBUG#ifdef SCPP_TEST_ASSERT_ON#define SCPP_TEST_ASSERT_ON(condition, msg) SCPP_ASSERT(condition, msg)#else#define SCPP_TEST_ASSERT_ON(condition, msg) // do nothing#endif // !SCPP_TEST_ASSERT_ON#endif // !_SCCP_ASSERT_H_

scpp_assert.cpp：

#include "stdafx.h"#include "scpp_assert.h"#include "iostream"#include "stdlib.h"#ifdef SCPP_THROW_EXCEPTION_ON_BUGnamespace scpp{ScppAssertFailedException::ScppAssertFailedException(const char *file_name, unsigned line_number, const char* message){std::ostringstream ss;ss << "SCPP assertion failed with message '" << message<< "' in file " << file_name << " #" << line_number;what_ = ss.str();}}#endif // SCPP_THROW_EXCEPTION_ON_BUGvoid SCPP_AssertErrorHandler(const char *file_name, unsigned line_number, const char *message){#ifdef SCPP_THROW_EXCEPTION_ON_BUGthrow scpp::ScppAssertFailedException(file_name, line_number, message);#elsestd::cerr << message << " in file " << file_name << " #" << line_number << std::endl << std::flush;exit(1);#endif // SCPP_THROW_EXCEPTION_ON_BUG}

 

测试程序：

// debug.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include "scpp_assert.h"#include "iostream"int _tmain(int argc, _TCHAR* argv[]){std::cout << "hello, SCPP_ASSERT" << std::endl;double stockPrice = 100.0;SCPP_ASSERT(0 < stockPrice && stockPrice <= 1.e6, "Stock price " << stockPrice << " is out of range");stockPrice = -1.0;SCPP_ASSERT(0 < stockPrice && stockPrice <= 1.e6, "Stock price " << stockPrice << " is out of range");return 0;}

这个宏可以合成一条有意义的错误，包括与错误有关的更多信息：

SCPP_ASSERT(0 < stockPrice && stockPrice <= 1.e6, 

"Stock price " << stockPrice << " is out of range");

 

而且在这个宏中，可以使用任何类的对象，只要他定义了<<操作符。比如：

#include "stdafx.h"#include "scpp_assert.h"#include "iostream"class MyClass{public:bool IsValid(bool flag){return flag == true ? true : false; }friend std::ostream& operator <<(std::ostream & os, const MyClass &obj);};inline std::ostream& operator <<(std::ostream & os, const MyClass &obj){return os;}int _tmain(int argc, _TCHAR* argv[]){std::cout << "hello, SCPP_ASSERT" << std::endl;MyClass obj;SCPP_ASSERT(obj.IsValid(false), "this object " << obj << " is invalid.");return 0;}

 

如果一开始定义了SCPP_THROW_EXCEPTION_ON_BUG那么，即是要打开安全检查，当检查多的时候，速度会有所下降。