What’s the deal with OLDNAMES.LIB?

栏目: IT技术 · 发布时间: 3年前

Set the time machine to 1988. The C language has not yet been standardized. Everybody had their own libraries for doing stuff, and some of them even pretended to be compatible with each other. The Microsoft C compiler, for example, came with a bunch of functions like unlink and stat to provide sort-of compatibility with Unix-sort-of source code.

And then the C standard was ratified in 1989. Now things got interesting, because those functions were not part of the C standard. Standard-conforming C programs were welcome to define functions with those names, and the rules say that this is perfectly legal and are not references to the identically-named Unix-like functions.

Now, there was a lot of code written for the Microsoft C toolchain that used these sort-of-Unix-ish functions, and renaming those functions would cause those programs to break.

So should we rename the Unix-ish functions in the Microsoft C library, in order to conform to the C standard? Or should we leave the functions in the Microsoft C library under their pre-standard names, to keep existing code working?

Let’s do both !

The Microsoft C library renamed these Unix-ish function to have a leading underscore. So unlink became _unlink , and so on. A program that didn’t use the Unix-ish library functions could define its own function called unlink , and everything would work just fine. But if the program actually wanted to use the unlink function from the Unix-ish library, this magic library OLDNAMES.LIB would step in.

The OLDNAMES.LIB library doesn’t contain any code of its own. Rather, it contains name redirections that say, “Hey, I have a symbol called unlink , in case you were looking for it. Wait, you want to know what this symbol represents? Um, it represents a symbol named _unlink . Good luck with that.”

If the linker cannot find a symbol named unlink , it turns to OLDNAMES.LIB as a library of last resort, and that library resolves the symbol unlink , but replaces it with an unresolved symbol named _unlink . The linker then goes through the symbol resolution process again, and this time it finds _unlink in the regular C library.

The net result is that your attempt to call the function unlink got redirected to the function _unlink , but only if you didn’t already have a function named unlink .

You can suppress the OLDNAMES.LIB library in various ways, most notably by passing the /NODEFAULTLIB flag, which can be abbreviated to the somewhat enigmatic /NOD .


以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持 码农网

查看所有标签

猜你喜欢:

本站部分资源来源于网络,本站转载出于传递更多信息之目的,版权归原作者或者来源机构所有,如转载稿涉及版权问题,请联系我们

JavaScript王者归来

JavaScript王者归来

月影 / 清华大学出版社 / 2008-7 / 86.00元

你手中的这本《JavaScript王者归来》不仅是一本传播知识的书,更是一本求道的书。 本书分为五个部分循序渐进地与读者讨论了JavaScript的方方面面,从简单的语言基础到丰富的实际应用再到深入剖析语言本质的高级话题,字里行间包含着作者多年工作中对JavaScript实践乃至程序设计思想的深入思考和总结。 本书揭开了JavaScript的面纱,绕过误解和虚幻的表象,引领你探索程序王......一起来看看 《JavaScript王者归来》 这本书的介绍吧!

CSS 压缩/解压工具
CSS 压缩/解压工具

在线压缩/解压 CSS 代码

在线进制转换器
在线进制转换器

各进制数互转换器

HEX HSV 转换工具
HEX HSV 转换工具

HEX HSV 互换工具