ch7-2008軟件工程七章編碼設計34

1、1（主講（主講 趙元哲）趙元哲）23456 數(shù)據(jù)結構的復雜性問題數(shù)據(jù)結構的復雜性問題 數(shù)據(jù)實時處理能力數(shù)據(jù)實時處理能力 數(shù)據(jù)庫操作問題數(shù)據(jù)庫操作問題78910111213141516171819202122nDefensive programmingDefensive programming is a form of defensive design intended is a form of defensive design intended to ensure the continuing function of a piece of software in spite to ensure

2、 the continuing function of a piece of software in spite of unforeseeable usage of said software. The idea can be of unforeseeable usage of said software. The idea can be viewed as reducing or eliminating the prospect of viewed as reducing or eliminating the prospect of Murphys LawMurphys Law having

3、 effect. Defensive programming techniques are used having effect. Defensive programming techniques are used especially when a piece of software could be misused especially when a piece of software could be misused mischievously or inadvertently to catastrophic effect.mischievously or inadvertently t

4、o catastrophic effect.nDefensive programmingDefensive programming is an approach to improve software and is an approach to improve software and source code, in terms of:source code, in terms of: General qualityGeneral quality - Reducing the number of software bugs and - Reducing the number of softwa

5、re bugs and blems. Making the source code comprehensibleMaking the source code comprehensible - the source code - the source code should be readable and understandable so it is approved in a should be readable and understandable so it is approved in a code audit.code audit. Making the so

6、ftware behave in a predictable manner despite Making the software behave in a predictable manner despite unexpected inputs or user actions.unexpected inputs or user actions.23n最常見的最常見的defensive programmingdefensive programming方法是加方法是加assertion(assertion(就是一種強制檢查就是一種強制檢查) )，比如比如: : 在訪問一個內(nèi)存地址之前，先檢查指向那里的指針是否在訪問一個內(nèi)存地址之前，先檢查指向那里的指針是否有效。有效。 在在win32win32平臺上可以加入平臺上可以加入，然后就可以，然后就可以用用assert(bool)assert(bool)這個函數(shù)。這個函數(shù)。 如果檢查出這里有錯，程序就會被中斷在這行語句處，如果檢查