连接两个共享库的一些相同的符号的 [英] linking two shared libraries with some of the same symbols

问题描述

我想用两个不同的共享库链接。这两个库定义共享的名称，但有不同的实现一些符号。我似乎无法找到一种方法，使每个库使用它自己的实现比其他。

I am trying to link with two different shared libraries. Both libraries define some symbols that share a name but have different implementations. I can't seem to find a way to make each library use its own implementation over the other.

例如，两个库定义全局函数巴（）每个内部调用。图书馆一位来自 foo1称之为（）和库从 foo2的两次调用它（）。

For example, both libraries define a global function bar() that each calls internally. Library one calls it from foo1() and library two calls it from foo2().

Lib1.so：

T bar
T foo1()     // calls bar()

Lib2.so：

Lib2.so:

T bar
T foo2()     // calls bar()

如果我链接到我的应用程序对Lib1.so然后Lib2.so从Lib1.so酒吧调用执行，即使被称为 foo2的（）。如果在另一方面，连结我针对Lib2.so然后Lib1.so应用，则棒总是从Lib2.so称为

If I link my application against Lib1.so and then Lib2.so the bar implementation from Lib1.so is called even when calling foo2(). If on the other hand, I link my application against Lib2.so and then Lib1.so, then bar is always called from Lib2.so.

有没有一种方法，使图书馆总是preFER自己的实现上述任何其他库？

Is there a way to make a library always prefer its own implementation above any other library?

推荐答案

有几种方法来解决这个问题：

There are several ways to solve this:

• 通 -Bsymbolic 或 -Bsymbolic函数 以连接器。这有一个全球性的影响：每一个引用全局符号（函数类型为 -Bsymbolic函数），可以解析到库中的元件被解析为一个符号。有了这个，你失去了干预内部库调用使用LD_ preLOAD这些符号的能力。 的符号仍然远销，这样他们就可以从库外被引用。

• Pass -Bsymbolic or -Bsymbolic-functions to the linker. This has a global effect: every reference to a global symbol (of function type for -Bsymbolic-functions) that can be resolved to a symbol in the library is resolved to that symbol. With this you lose the ability to interpose internal library calls to those symbols using LD_PRELOAD. The symbols are still exported, so they can be referenced from outside the library.

使用的版本脚本标记符号的本地的图书馆，例如使用类似： {地方：酒吧;}; 并通过 - 版本脚本= versionfile 来的链接。 的符号的不的出口。

Use a version script to mark symbols as local to the library, e.g. use something like: {local: bar;}; and pass --version-script=versionfile to the linker. The symbols are not exported.

与approppiate 可视性标志符号（<一个href=\"http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html#index-g_t_0040$c$c_007bvisibility_007d-attribute-2535\">GCC信息页面能见度），这将是任何的隐藏的内部或保护的。 保护的的知名度符号的导出为 .protected 隐藏的符号不导出和 内部的符号不导出并您妥协不是从图书馆外面打电话给他们，即使是间接地通过函数指针

Mark symbols with an approppiate visibility (GCC info page for visibility), which will be either hidden, internal, or protected. protected visibility symbols are exported as .protected, hidden symbols are not exported, and internal symbols are not exported and you compromise not to call them from outside the library, even indirectly through function pointers.

您可以检查哪些符号与 objdump的-T 导出。

You can check which symbols are exported with objdump -T.

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