admin管理员组

文章数量:1794759

Item 20: Facilitate the return value optimization.(More Effective C++)

Item 20: Facilitate the return value optimization.(More Effective C++)

The rules for C++ allow compilers to optimize temporary objects out of existence. As a result, if you call operator* in a context like this,

Rational a = 10;  Rational b(1, 2);  Rational c = a * b; // operator* is called here

your compilers are allowed to eliminate both the temporary inside operator* and the temporary returned by operator*. They can construct the object defined by the return expression inside the memory allotted for the object c. If your compilers do this, the total cost of temporary objects as a result of your calling operator* is zero: no temporaries are created. Instead, you pay for only one constructor call — the one to create c. Furthermore, you can't do any better than this, because c is a named object, and named objects can't be eliminated

转载于:wwwblogs/zhtf2014/archive/2012/03/09/2387538.html

本文标签： facilitateItemEffectiveoptimizationreturn

版权声明：本文标题：Item 20:Facilitate the return value optimization.(More Effective C++) 内容由林淑君副主任自发贡献，该文观点仅代表作者本人， 转载请联系作者并注明出处：http://www.xiehuijuan.com/baike/1686986873a125736.html， 本站仅提供信息存储空间服务，不拥有所有权，不承担相关法律责任。如发现本站有涉嫌抄袭侵权/违法违规的内容，一经查实，本站将立刻删除。