如何提供的libc职能，两个人的名字？ [英] How does libc provide functions with two names?

问题描述

在直接结合（-B直接）libc中的出现提供了许多
         有两个名字的功能。例如，的getpwent（）和_getpwent（）。
         这两个名字所指正是libc中的相同的功能。

Before the advent of direct binding (-B direct) libc provided many functions with two names. For example, getpwent() and _getpwent(). These two names referred to exactly the same function in libc.

如何libc中提出两个函数名指向相同的实现？

How does libc make two function names point to the same implementation?

我觉得应该不会像写作一样code虽然两次一样容易。

I think it should not be as easy as writing the same code twice though.

推荐答案

它可以通过完成的弱别名的一个非标准连接把戏，一直围绕年初以来，Unix系统，并可以被所有UNIX编译器/连接器支持我知道。它基本上做的：

It's done via weak aliases a "nonstandard" linker trick that's been around since early unices and that's supported by all unix compilers/linkers I know of. It's basically done as:

void __foo(void);
void foo(void) __attribute__((weak, alias("__foo")));

经常与宏抽象的那么一点点。这使得它，因此象征富将具有相同的地址和类型符号 __富默认，但允许它由强的定义在别处被覆盖。

often with macros to abstract it a little bit. This makes it so the symbol foo will have the same address and type as the symbol __foo by default, but allows it to be overridden by a "strong" definition somewhere else.

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